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  • 1970-1974  (742)
  • 1920-1924
  • Ultrastructure  (453)
  • Physical Chemistry  (289)
  • 101
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 6 (1974), S. 371-382 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the thermal decomposition of diallylamine to propylene and prop-2-enaldimine have been studied in the gas phase in presence of an excess of methylamine over the temperature range of 532.7 to 615.6°K, using a static reaction system. Methylamine reacted with the unstable primary product prop-2-enaldimine, forming the thermally stable N-methyl prop-2-enaldimine.First-order rate constants, based on the internal standard technique, fit the Arrhenius relationship log k(s-1) = (11.04 ± 0.13) - (37.11 ± 0.33 kcal/mole)/2.303 RT. They were independent on the initial total pressure (46-340 torr), the initial pressure of diallylamine (9.2-65 torr), or methylamine as well as the conversion attained. Despite an apparent surface sensitivity, the reaction is essentially homogeneous in nature as demonstrated by experiments carried out in a packed reaction vessel.The observed activation parameters for the title reaction together with those observed earlier for triallylamine and allylcyclohexylamine are consistent with the proposed concerted reaction mechanism involving a cyclic 6-center transition state. The observed substituent effects suggest a nonsynchronous mode of bond breaking and bond formation.
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  • 102
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 6 (1974) 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 103
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 6 (1974), S. 457-466 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Activation energies for substitution reactions of the type AC + B → A + CB, occurring in polar media and characterized by an abrupt change of the term along two coordinates have been calculated within the framework of the quantum-mechanical theory of chemical reactions. In the case of nonadiabatic processes, the transmission coefficient and activation energy for these reactions are expressed in terms of characteristic parameters of the medium (reorganization energy, effective frequency of solvent fluctuation polarization) and the potential energy curves for intermolecular interactions between the reactants (AC and B) and between the products (A and BC).
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  • 104
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal decomposition of ethylallylether (EAE) has been studied in the gas phase over the temperature range of 560-648°K. Propylene and acetaldehyde are the only reaction products observed. The reaction is apparently homogeneous in nature and independent of the pressure of EAE and of added foreign gases. The experimetally determined first-order rate constants, using the internal standard technique, fit the Arrhenius relationship log k(s-1) = 11.84 ± 0.29 - (43.57 ± 0.77 kcal/mole)/2.303RT. Independently the same rate constants are obtained, based on the amounts of products formed. The observed activation parameters are in general agreement with expectations based on the concept of a 6-center 1,5-H-shift retro-“ene” reaction mechanism, and they agree with previous results obtained for the similar reactions involving alkylallylamines and olefins.
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  • 105
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 6 (1974), S. 453-456 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A competitive method involving the direct measurement of radical concentrations by EPR spectroscopy has been used to show that in solution at 25°C the rate constants for the bimolecular self-reactions of ethyl, isopropyl, tert-butyl, cyclopentyl, and trichloromethyl are all approximately equal, as had been indicated previously by direct measurement of the rate constants for decay of these radicals.
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  • 106
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 6 (1974), S. 507-516 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Predictions of the “redox” and “complex” schemes for the Fe3+ catalyzed decomposition of H2O2 have been compared with published and new experimental data by numerical integratior of the appropriate complete sets of differential equations. Apparent discrepancies for the redox scheme at high Fe3+/H2O2 ratios are shown to disappear in the complete treatment, and inconsistencies of the complex scheme with both kinetic data and spectroscopic measurements are pointed out.
    Additional Material: 7 Ill.
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  • 107
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 6 (1974), S. 531-543 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of reactant self-heating or cooling upon rate data is considered, and three approaches to the problem of obtaining valid kinetic parameters are described in detail. A comparison of these approaches emphasises the need to assess and allow for thermal effects during the initial planning of kinetic experiments if satisfactory results are to be acquired. An integrated rate expression is given for use with nonisothermal data, and is used to provide correction factors for rate constants which have been derived without allowance for thermal effects.
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  • 108
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 6 (1974), S. 553-565 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of O(3P), prepared from the Hg photosensitization of N2O, with C2HCl3 was studied at 25°C. The products of the reaction in the absence of O2 were CO, CHCl3, and polymer (as well as N2 from the N2O). The quantum yields of CO and CHCl3 were 0.23 ± 0.01 and 0.14 ± 0.05, is respectively independent of reaction conditions. The reaction mechanism is with k14a/k14 = 0.23, where k14a + k14b. Most of the HCl and CCl2 combine to form CHCl3, but some other products must also be formed to account for the difference in the CO and CHCl3 quantum yields. The C2HCl3O* adduct polymerizes without involving additional C2HCl3 molecules, since the quantum yield of C2HCl3 disappearance, —Φ{C2HCl3}, was about 1.0 at high values of [N2O]/[C2HCl3]. The rate coefficient for the reaction of O(3P) with C2HCl3 is 0.10 that for the reaction of O(3P) with C2F4.In the presence of O2 the free radical chain oxidation occurs because of the reaction The main product is CHCl2CCl(O) with smaller amounts of CO and CCl2O, and some CO2. The chain lengths were long and values of — Φ {C2HCl3} up to 90 were observed.
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  • 109
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 6 (1974), S. 587-595 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the decay of hydroxyl radicals in the presence of excess acetylene were studied at pressures in the vicinity of 1 torr and at ambient temperature in a tubular discharge-flow reactor. Hydroxyl radicals were produced by the reaction of atomic hydrogen with nitrogen dioxide, H + NO2 → OH + NO. The concentration of hydroxyl was followed by line absorption photometry at 308.939 nm and 308.328 nm. Second-order rate coeffcients were determined in two sets of experiments. The initial concentration ratio [C2H2]0/[OH]0 was in the range of 2.3 to 13.2 in the first set, and 14 to 125 (owing to greater hydroxyl detection sensitivity) in the second set. Values of the second-order rate coefficient obtained were nk5 = (2.9 ± 0.3) × 10-13 cm3/molec-sec in the first set, and nk5 = (2.1 ± 0.6) × 10-13 cm3/molec-sec in the second set, where n is the stoichiometric coefficient of OH. A value of the bimolecular rate constant k5 = (2.0 ± 0.6) × 10-13 cm/molec-sec is consistent with both sets of data, as well as an earlier determination.
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  • 110
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 6 (1974) 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 111
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 6 (1974), S. 631-641 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal decomposition of t-butylmethyl ether has been studied using the VLPP technique. The recommended Arrhenius parameters for the molecular elimination, reaction (1), are A(800°K) = 101 3, 9 sec-1 and Ea (800°K) = 59.0 ± 1.0 kcal/mole. No radical reactions occur under the conditions used. These parameters are in good agreement with earlier experimental work and with theoretical estimates of both A and E.
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  • 112
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 6 (1974), S. 829-848 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chemical reactions of SO2(3B1) molecules with cis- and trans-2-butene have been studied in gaseous mixtures at 25°C by excitation of SO2 within the SO2(3B1) → SO2(+, 1A1) ‘forbidden’ band using 3500-4100-Å light. The initial quatum yields of olefin isomerization were determined as a function of the [SO2]/[2-butene] ratio and added gases, He and O2. The kinetic treatment of these data suggests that there is formed in the SO2(3B1) quenching step with either cis- or trans-2-butene, some common intermediate, probably a triplet addition complex between SO- and olefin. It decomposes very rapidly to form the 2-butene isomers in the ratio [trans-2-butene]/[cis-2-butene] = 1.8. In another series of experiments SO2 was excited using a 3630 ± 1-Å laser pulse of short duration, and the SO2(3B1) quenching rate constants with the 2-butenes were determined from the SO2(3B1) lifetime measurements. The rate constants at 21°C are (1.29 ± 0.18) × 1011 and (1.22 ± 0.15) × 1011 l/mole·sec with cis-2-butene and trans-2-butene, respectively, as the quencher molecule. Within the experimental error these quenching constants equal those derived from the quantum yield data. Thus the rate-determining step in the isomerization reaction is suggested to be the quenching reaction, presumably the formation of the triplet SO2-2-butene addition complex. In a third series of experiments using light scattering measurements, it was found that the aerosol formation probably originates largely from SO3 and H2SO4 mist formed following the reaction SO2(3B1) + SO2 → SO3 + SO(3Σ-). Aerosol formation from photochemically excited SO2-olefin interaction is probably unimportant in these systems and must be unimportant in the atmosphere.
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  • 113
    Electronic Resource
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    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 6 (1974), S. 887-891 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The decaying absorption of CH3 radicals at 216.4 nm has been followed over more than three half-lives using a photoelectric split-beam kinetic spectrometer. The rate constant for recombination kr was found to be (5.60 ± 0.76) × 10-11 cm3/molecule·s.
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  • 114
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    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 6 (1974), S. 899-920 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Singlet methylene was reacted with cyclopentadiene to give chemically activated bicyclo[3.1.0]hex-2-ene (BCH). The rate of isomerization of BCH to 1,4-cyclohexadiene, 1,3-cyclohexadiene, cis-1,3,5-hexatriene, and l-methylcyclopentadiene is compared with calculated rate constants using the RRKM theory and measured or estimated thermal Arrhenius parameters. Subsequent isomerizations of the C6H8 products are also measured and calculated. These include 1,4-cyclohexadiene to benzene and the reversible reactions between 1,3-cyclohexadiene, cis-1,3,5-hexatriene, and trans-1,3,5-hexatriene. The results provide new data for several of these reactions which have not been observed in thermal studies. Agreement between the observed and calculated rates using the strong collision assumption is satisfactory except for the trans-1,3,5-hexatriene to cis-1,3,5-hexatriene reaction.
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  • 115
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 6 (1974), S. 813-828 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Study of the reaction by very-low-pressure pyrolysis (VLPP) in the temperature range of 550-850°K yields for the high-pressure Arrhenius parameters \documentclass{article}\pagestyle{empty}\begin{document}$$\log {\rm }\,k_{\rm 1} = (15.6 \pm 0.5) - (36.0 \pm 1.0)/\theta {\rm \,(sec}^{{\rm - 1}})$$\end{document} where θ = 2.303RT in kcal/mole. These in turn yield for the high-pressure second-order recombination of tBu + NO, k-1 = (3.5 ± 1.7) × 109 1./mole·sec at 600°K. For the competing reaction l./mole·sec and E4 ≥ 4.2 kcal/mole. The bond dissociation energy DHo (tBu-NO) was determined to be (39.5 ± 1.5) kcal/mole, both from the equilibrium constant and from the activation energy of reaction (1), obtained from RRKM calculations. A ‘free-volume’ model for the transition state for dissociation is consistent with the data. A limited study of the system at 8-200 torr showed an extremely rapid inhibition by products and a very complex set of products.
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  • 116
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    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 6 (1974), S. 875-876 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 117
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    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 6 (1974), S. 893-897 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal isomerization of 1,1-divinylcyclopropane has been investigated in the gas phase in the temperature range of 238 to 288°C and for pressures in the range of 4 to 12 torr. The isomerization to 1-vinylcyclopentene is homogeneous and kinetically first order and almost certainly unimolecular. The rate constants yield the Arrhenius equation \documentclass{article}\pagestyle{empty}\begin{document}$$\log {\rm }k({\rm s}^{ - 1} {\rm)} = 13.53 \pm 0.13 - (42.45 \pm 0.33{\rm \,kcal/mole})/RT\,{\rm In 10}$$\end{document} or \documentclass{article}\pagestyle{empty}\begin{document}$$\log {\rm }k({\rm s}^{ - 1} {\rm)} = 13.53 \pm 0.13 - (117.6 \pm 1.4{\rm \,kJ/mole})/RT\,{\rm In 10}$$\end{document} The assumption of a similar transition state for this isomerization with that of l-methyl-l-vinylcyclopropane leads to a value for an alkylpentadienyl radical stabilisation energy of 19.2 ± 1.6 kcal/mole (80.4 ± 6.7 kJ/mole), and this value is compared with other estimates.
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  • 118
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    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 6 (1974), S. 15-28 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The oxidation of inositol by quinquevalent vandadium in acid medium is a first-order reaction both in vanadium (V) and inositol. The stoichiometry of the reaction is consistent with the use of two equivalents of vanadium (V) per mole of inositol with the formation of one mole of inosose. The reaction is catalyzed both by sulfuric and perchloric acid, but the rate is faster in sulfuric acid than in perchloric acid. In 1M-6M perchloric acid solutions the reaction has shown a variable order in H+, but in solutions of 2M-5M sulfuric and perchloric acid of constant ionic strength, the rate has a linear dependence on [H+]2. There is also a linear correlation between the rate and bisulfate ions in sulfuric acid at constant hydrogen ion concentration. The energy of activation is found to be 19 kcal/mole and a negative entropy value of - 14 e.u. A suitable mechanism, consistent with the kinetics in 2M-5M acid solutions, is suggested and the values of various rate constants are evaluated.
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  • 119
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Very strong laser emission at 5 μm was detected when SO2 and CHBr3 were flash photolyzed in the vacuum ultraviolet (λ ≥ 165 nm) in the presence of a large amount of diluent (SF6, He, or Ar). About 110 vibration-rotation transitions ranging from Δv = 18 → 17 to 3 → 2, except 16 → 15, were identified. The primary reactions leading to the CO stimulated emission are as follows: The product analysis results and the variation of laser intensity with flash energy and SO concentration indicate that the following side reactions are also occurring. Addition of a small amount of O2 enhances the laser output by both eliminating these side reactions and simultaneously producing vibrationally excited CO via reaction (8), which has been previously shown to generate CO stimulated emission. The effects of various reactive (NO and H2) and inert (He, Ar, SF6, CO, N2, N2O, and CO2) gases have been examined. All additives (P ≤ 20 torr), except NO and H2, increase the total laser output. N2O enhances the power most efficiently, whereas CO, N2, and CO2 are less effective and have similar efficiencies. The enhancement of the laser intensity by these near-resonant gases is ascribed to the depletion of CO population at lower levels which thus increases the rates cascading from higher levels. NO and H2 quench the laser output by chemically reducing the concentration of the CH radical.
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  • 120
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    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 6 (1974), S. 61-75 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A kinetic study of lead atoms in the spin orbit states, Pb(63P1) and Pb Pb(63P2), 0.969 and 1.320 eV, respectively, above the 63P0 ground state, has been carried out by atomic absorption spectroscopy. The electronically excited lead atoms were generated by the pulsed irradiation of lead tetraethyl and monitored photoelectrically by time-resolved attenuation of resonance radiation. The decay of the two atomic states has been studied in the presence of He, Ar, H2, D2, N2, O2, CO, NO, CO2, N2O, CH4, C2H4, C2H2 CF4, SF6, and PbEt4, and rate constants for the collisional quenching by these gases are reported. The resulting data are compared with those for the deactivation of other atomic spin orbit states of comparable energy. In general, the higher energy state, Pb(63P2), is found to be deactivated more rapidly. It would appear that the magnitude of the electronic energy to be transferred on collision governs the rates of quenching, at least where a weak interaction potential is involved, and that for most gases, deactivation of Pb(63P2) proceeds via Pb(63P1).
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  • 121
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation and characterization of the iron(II) complex of the hexadentate Schiff base ligand NN‴-bis-[α-(2-pyridyl)benzylidene]triethylenetetramine are reported. Kinetic patterns and rate constants for aquation of this complex, and for its reactions with hydroxide, cyanide, and peroxodisulphate have been determined. Activation parameters for the reaction with cyanide, in aqueous solution, are ΔH
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  • 122
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    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 6 (1974), S. 169-228 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methods are discussed for the production and detection of the hydroperoxyl radical for use in gas phase kinetic studies. Rate constants for gas phase reactions of the hydroperoxyl radical with itself, H2, H2O, CO, NO, SO2, O3, C2H6, C3H8, i-and n-C4H10, C2H4, i-C4H8, HCHO, C2H5CHO, n-C3H7CHO, Br, O, OH, and H are critically evaluated. Recommended or estimated rate constant expressions with associated error limits are given applicable over specified temperature ranges (normally 300-1000°K). The reactivity of HO2 compared with OH, O, H, F, Cl, Br, CH3, and CH3O is presented in tabular form and the implications for atmospheric chemistry are discussed.
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  • 123
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    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 6 (1974), S. 257-263 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The pyrolysis of C6F5I has been studied by the toluene carrier method over the temperature range of 900-978°K with contact times of 0.4-2.0 seconds and total pressures of 11.2-19.5 torr. Percent decomposition ranged from 8.6 to 97.7%. With toluene-to-C6F5I molar ratios of greater than 150, 85-100% of the C6F5 released abstracts a hydrogen atom from toluene to produce C6F5H. No significant quantities of I2 were observed and the only major gaseous product was HI. Within the limits of the experimental method the decomposition of C6F5I was first order and homogeneous.Least squares analysis of log k1 and 103/T(C6F5I → C6F5 + I) values gives \documentclass{article}\pagestyle{empty}\begin{document}$${\rm log}\,k_1 ({\rm s}^{- 1}) = 15.9 - 69,200/4.576T $$\end{document} while a weighted line of best fit yields. \documentclass{article}\pagestyle{empty}\begin{document}$${\rm log}\,k_1 ({\rm s}^{- 1}) = 15.4 - 67,000/4.576T$$\end{document} Based on this latter equation D[C6F5—I] at 298°K is estimated as 66.2 kcal/mole.
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  • 124
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    International Journal of Chemical Kinetics 6 (1974), S. 265-277 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the gamma-radiation-induced free radical chain reaction in solutions of C2Cl3F in cyclohexane (RH) was investigated over a temperature range of 87.5-200°C. The following rate constants and rate constant ratios were determined for the reactions: \documentclass{article}\pagestyle{empty}\begin{document}$$\begin{array}{*{20}c} {{\rm (2a)}} & {{\rm R} + {\rm C}_{\rm 2} {\rm Cl}_{\rm 3} {\rm F} \to {\rm RCClFCCl}_{\rm 2}} \\ \end{array}$$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$\begin{array}{*{20}c} {(2{\rm b})} & \to \\ \end{array}{\rm RCCl}_{\rm 2} {\rm CClF}$$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$\begin{array}{*{20}c}{{\rm (3a)}} & {{\rm RCClFCCl}_{\rm 2} \to {\rm RCF}}\\ \end{array}{\raise1pt\hbox{$\Relbar \kern-4pt{\Relbar}$}}{\rm CCl}_{\rm 2} + {\rm Cl}$$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$\begin{array}{*{20}c} {{\rm (4a)}} & {{\rm RCClFCCl}_{\rm 2} + {\rm RH} \to {\rm RCClFCCl}_{\rm 2} {\rm H} + {\rm R}} \\ \end{array}$$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$\log {\rm }k_{2a} ({\rm mole}^{{\rm - 1}} 1.\,{\rm sec}^{{\rm - 1}}) = (8.64 \pm 0.35) - (6.38 \pm 0.41)/\theta ^1$$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$\log {\rm }k_{{\rm 2b}} /k_{{\rm 2a}} = (- 0.03 \pm 0.15) - (2.39 \pm 0.28)/\theta$$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$\log {\rm (}k_{3{\rm a}} /k_{4{\rm a}})({\rm mole}\,1.^{{\rm - 1}}) = (6.17 \pm 0.10) - (10.14 \pm 0.18)/\theta$$\end{document} In competitive experiments in ternary solutions of C2Cl4 and C2Cl3F in cyclohexane the rate constant ratio k2c/k2a was determined \documentclass{article}\pagestyle{empty}\begin{document}$$\begin{array}{*{20}c} {{\rm (2c)}} & {{\rm R} + {\rm C}_{\rm 2} {\rm Cl}_{\rm 4} \to {\rm RC}_{\rm 2} {\rm Cl}_{\rm 4}} \\ \end{array}$$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$\log {\rm }k_{{\rm 2c}} /k_{{\rm 2a}} = (0.13 \pm 0.06) - (1.20 \pm 0.12)/\theta$$\end{document} By comparing with previous data for the addition of cyclohexyl radicals to other chloroethylenes it is shown that in certain cases the trends in activation energies for cyclohexyl radical addition can be correlated with the C—Cl bond dissociation energies in the adduct radicals.
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  • 125
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    International Journal of Chemical Kinetics 6 (1974), S. 323-336 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The substitution of N-alkyl substituted ethylenediamines for chloride ions in the rapidly equilibrating system \documentclass{article}\pagestyle{empty}\begin{document}$${\rm PdCl}_{\rm 4} ^{{\rm 2 - }} {\rm + H}_{\rm 2} {\rm O}\rightleftharpoons{\rm PdCl}_{\rm 3} ({\rm H}_2 {\rm O)}^{\rm - } + {\rm Cl}^{\rm - }$$\end{document} has been investigated in aqueous acid medium. The kinetic data can be accommodated by the general rate law \documentclass{article}\pagestyle{empty}\begin{document}$$k_{{\rm obs}} = \left\{ {\frac{k}{{\left[{{\rm H}^{\rm + }} \right]}} + \frac{{k'}}{{\left[{{\rm H}^{\rm + } } \right]\left[{{\rm Cl}^{\rm - } } \right]}}} \right\}\left[{{\rm N}_{\rm n} {\rm N}_{\rm m} {\rm en}} \right]_{{\rm total}}$$\end{document} where n = 0, 1, or 2 and m = 0, 1, or 2, depending on whether none, one, or two methyl groups are attached to the two nitrogen atoms of ethylenediamine. Reaction with the most heavily substituted ethylenediamine, namely, N2N2en discloses a change of the mentioned rate law to \documentclass{article}\pagestyle{empty}\begin{document}$$k_{{\rm obs}} = \left\{ {\frac{{k''}}{{\left[{{\rm H}^{\rm + } } \right]}} + \frac{{k'''\left[{{\rm Cl}^{\rm - } } \right]}}{{\left[{{\rm H}^{\rm + } } \right]}}} \right\}\left[{{\rm N}_{\rm 2} {\rm N}_{\rm 2} {\rm en}} \right]_{{\rm total}}$$\end{document} on going from a lower to a higher chloride ion concentration range. This change in the mathematical form of the rate law can be explained in terms of an ion-pair association of N2N2enH+ and free chloride ions.
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  • 126
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    International Journal of Chemical Kinetics 6 (1974), S. 383-394 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An inhibitor method for measuring the initiation rate is proposed for the system Fe3+ + H2O2. C(NO2)4 was used as inhibitor. The number of chains terminated by one C(NO2)4 molecule was estimated in specific photochemical experiments and found to be unity. The initiation appeared to involve two processes. The first is proportional to the first power of ferric ion concentration, and the second to the second power. The rate constants and activation energies of these processes are determined. Allowance for the second initiation process permitted qualitative and quantitative description of various reported data on H2O2 decomposition rates over a wide range of Fe3+, H2O2, and H+ concentrations.
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  • 127
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    International Journal of Chemical Kinetics 6 (1974), S. 493-506 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of the addition of hydrogen chloride on the photolysis of carbon tetrachloride in the presence of cyclohexane has been investigated in a companion paper. The data enable the rate constant ratio k8/(k5)1/2 to be determined. Since k-8 is well established, k5 can be estimated from known thermochemical data. The validity of the thermochemical derivation is checked by applying it to trifluoromethyl radicals. The photolysis of bromotrichloromethane and carbon tetrachloride in the presence of hydrogen chloride has been investigated over a range of temperatures. From these results and assuming reaction (5) has no activation energy, Arrhenius parameters for reaction (8) have been determined: The activation energies for the reaction of methyl, trichloromethyl, and trifluoromethyl radicals with hydrogen chloride are compared, and at first sight surprising results are rationalized in terms of relative electronegativity.
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  • 128
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    International Journal of Chemical Kinetics 6 (1974), S. 527-530 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Measurements of rates of oxygen absorption and steady-state peroxy radical concentrations for the autoxidation of tetralin in the presence of tert-butyl hydroperoxide have shown that the rate constant for reaction of the tert-butylperoxy radical with tetralin at 60°C is approximately 11.0 M-1 s-1. This rate constant is about a factor of 4 larger than the value recently reported by Niki, Okayasu, and Kamiya for this reaction.The present work emphasizes that great care should be taken when the hydroperoxide method is used to estimate cross-propagation rate constants for a substrate as reactive as tetralin at a temperature as high as 60°C.
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  • 129
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    International Journal of Chemical Kinetics 6 (1974), S. 567-572 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The decomposition of acetylenedicarboxylic acid in acetophenone was studied in the temperature range of 100-130°C. The rate constants and activation parameters for the consecutive pair of first-order steps (each yielding carbon dioxide) were calculated. Hydrogen kinetic isotope effects were also studied. Comparisons were made with the decompositions of oxalic acid and malonic acid. An intramolecular H—C transfer is believed to be the main part of the reaction coordinate in addition to the C—C bond breaking.
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  • 130
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    International Journal of Chemical Kinetics 6 (1974), S. 777-786 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chloroethanes react with aqueous caustic to yield either elimination or substitution products. The reaction rates were measured for the dichloroethanes, trichloroethanes, tetrachloroethanes, and pentachloroethane between 283 and 353°K. The constants of HCl eleminations referring to the rate equation \documentclass{article}\pagestyle{empty}\begin{document}$$r = k[{\rm OH}^{\rm - }][{\rm dissolved \,substrate]}$$\end{document} are given by \documentclass{article}\pagestyle{empty}\begin{document}$${\rm 1,2 - C}_{\rm 2} {\rm H}_{\rm 4} {\rm Cl}_{\rm 2} {\rm }\,k = 10^{10.99 \pm 0.03} \exp (- 23,000 \pm 50RT)$$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$${\rm 1,1,2 - C}_{\rm 2} {\rm H}_{\rm 3} {\rm Cl}_{\rm 3} {\rm}\,k = 10^{13.99 \pm 0.03} \exp (- 22,400 \pm 50/RT)$$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$${\rm 1,1,1,2 - C}_{\rm 2} {\rm H}_{\rm 2} {\rm Cl}_{\rm 4} {\rm }\,k = 10^{15.45 \pm 0.14} \exp (- 25,800 \pm 210/RT)$$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$${\rm 1,1,2,2 - C}_{\rm 2} {\rm H}_{\rm 2} {\rm Cl}_{\rm 4} {\rm }\,k = 10^{16.40 \pm 0.05} \exp (- 22,550 \pm 70/RT)$$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$${\rm C}_{\rm 2} {\rm HCl}_{\rm 5} {\rm }\,k = 10^{12.50 \pm 0.08} \exp (- 15,200 \pm 110/RT)$$\end{document} all rate constants being in 1./mole·s and R in cal/mole· deg.With ethyl chloride, 1,1-dichloroethane, and 1,1,l-trichloroethane, the elimination is not observed and a slow substitution takes place. The influence of chlorine substituents on both sides of the molecule on mechanism and rate parameters is discussed.
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  • 131
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    Topics: Chemistry and Pharmacology
    Notes: The occurrence of anchimeric assistance in the vapor-phase thermolysis of anti- and syn-7-acetoxy-7-methylnorbornene and 7-acetoxy-7-methylnorborane has been investigated. The relative rates of thermolysis were found to be 1.9, 0.87, and 1.0, respectively. The nature of the transition state for ester thermolysis is discussed in light of the small amount of anchimeric assistance found in the thermolysis of the anti-isomer.
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  • 132
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    International Journal of Chemical Kinetics 6 (1974), S. 877-885 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The heats of formation of C3 and C4 alkyl nitrites (RONO) have been determined via their heats of combustion by bomb calorimetry, thereby providing a complete set of values of ΔHºf for C1-C4 alkyl nitrites. The experimental values are in excellent agreement with values derived from group additivity rules. For branched compounds these calculations involve corrections for gauche interactions. In these cases, the gauche interactions are reflected in the activation energies E1 determined by recent kinetic studies, required for breaking the RO-NO bond. The heats of formation of the alkoxy radicals involved together with ΔHºf(NO) = 21.6 kcal/mole leads to the result D(RO-NO) = 41.5 ± 1 kcal/mole. The concordance between D(thermochemical) and D(kinetic), unlike previous kinetic studies, implies that E2 = 0 ± 1 kcal/mole.
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  • 133
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    International Journal of Chemical Kinetics 6 (1974), S. 337-357 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Absolute values of the rate constants for the reaction of hydrogen atoms with cyclic olefins in the gas phase have been measured in a discharge-flow system under 3.5, 16, and 22 torr Ar at 23°C. The attenuation of hydrogen atom concentration in the reaction tube in the presence of a large excess of olefin was measured with an ESR spectrometer, and the products were analyzed by gas chromatography. Cyclic C6 hydrocarbons were the only significant products obtained when the hydrogen atom concentration was 2.6 × 10-10 mole/1., the olefin concentration was in the range of 9 to 22 × 10-8 mole/1., and the pressure was 16 torr Ar. The values for the rate constants for reaction with cyclohexadiene-1,3, cyclohexadiene-1,4, and cyclohexene are, respectively, (9 ± 2) × 108, (12 ± 1) × 108, and (6 ± 1) × 108 l./mole-sec, and they are not changed significantly by a sixfold change in total pressure. The fraction of the total interaction that proceeds by addition is 84% in the cyclohexadiene-1,3 system, but only 18% in the cyclohexadiene-1,4 system, and the cyclohexadienyl radical is therefore the dominant radical species in the latter system. The pattern of interaction between the hydrogen atom and the cyclohexadienyl radical was determined, and comprises 65% of disproportionation, and 13% and 23% of combination to yield cyclohexadiene-1,3 and cyclohexadiene-1,4, respectively. These results are consistent with the general patterns of reactivity emerging from studies of the reactions between free radicals and olefins in related systems.
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  • 134
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    International Journal of Chemical Kinetics 6 (1974), S. 395-400 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Different possible mechanisms for the gas phase reaction of formation of bromine chloride from bromine and chlorine are discussed. The rate of the reaction has been deduced from photometric measurements in conventional static reactors of surface-to-volume ratio ranging between 0.6 and 3 cm-1, at temperatures between 51 and 113°C. Experimental data show that (1) the observed reaction is predominantly heterogeneous, and (2) the homogeneous reaction must proceed by an atomic chain mechanism initiated by Br atoms.
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  • 135
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    International Journal of Chemical Kinetics 6 (1974), S. 417-428 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the reaction between ozone and allene (A) were studied in the range of 226 to 325°K in the gas phase. Initial O3 pressures varied from 0.01 to 0.7 torr and allene pressures varied from 0.05 to 6 torr. At the higher initial O3 pressures the most important product was O2 followed by CO, H2O, CO2, and C2H4. Oxygen balances averaging about 110% were obtained, which implies that no important oxygenated products were missed. However, carbon balances were only about 50% and hydrogen balances were even less, so that unidentified hydrocarbons were presumably formed. The rate law found was - d[O3]/dt = k1[O3][A] + k2a[O3]2[A]/[O3]0 where log k1(M-1sec-1) = 6.0 ± 0.7 - (5500±1000)/2.30RT and log k2a(M-1sec-1) = 6.9 ± 0.7 - (6200 ± 800/2.30RT). A mechanism is proposed which accounts for the rate law and the observed stoichiometry of O2 formed-O3 used. This involves a heterogeneous catalyzed decomposition of O3. The rate constant k1 is identified with the primary addition reaction A + O3 → AO3, and this rate constant is compared with those from other O3 addition reactions.
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  • 136
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    International Journal of Chemical Kinetics 6 (1974), S. 401-416 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using the technique of flash photolysis-resonance fluorescence, absolute rate constants have been measured for the reaction H + O2 + M → HO2+M over a temperature range of 220-360°K. Over this temperature range, the data could be fit to an Arrhenius expression of the following form: \documentclass{article}\pagestyle{empty}\begin{document}$$k_{{\rm Ar}} = (6.75{\rm } \pm {\rm }1.1){\rm } \times {\rm }10^{ - 33} \exp {\rm }[685{\rm } \pm {\rm }128{\rm cal/mole]/}RT$$\end{document} The units for kAr are cm6/mole-s. At 300°K the relative efficiencies for the third-body gases Ar:He:H2:N2:CH4 were found to be 1.0:0.93:3.0:2.8:22. Wide variations in the photoflash intensity at several temperatures demonstrated that the reported rate constants were measured in the absence of other complex chemical processes.
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  • 137
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    International Journal of Chemical Kinetics 6 (1974), S. 481-492 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photolysis of azocyclohexane, carbon tetrachloride, and cyclohexane at 360 nm has been investigated over a wide temperature range. At moderate temperatures a chain reaction ensues from which the following approximate rate constants could be determined assuming 2CCl3. → C2Cl6, k5 = 109.7 (303-673K): The really striking feature of the results is that they show that termination in bicyclohexyl [reaction (7)] is extremely slow: The root-mean-square rule for estimating the cross-combination rate is also followed.The photolysis of carbon tetrachloride and cyclohexane at 250 nm has also been investigated. The reaction is complicated by the occurrence of two concurrent photolytic processes, the main one yielding trichloromethyl radicals and chlorine atoms, and the subsidiary one yielding dichlorocarbene and molecular chlorine. Nonetheless the results from this reaction can be interpreted in the medium temperature range 360-430K, where long chains are present, in terms of the rate constants derived from the azocyclohexane system.
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  • 138
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    International Journal of Chemical Kinetics 6 (1974), S. 517-526 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photochemistry of 1,1,1-trifluoromethylazomethane has been partially characterized. The quantum yield for N2 formation from photolysis at 366 nm and room temperature was unity at low pressure and decreased to 0.5 at 630 torr. At room temperature the principal products were C2H6, C2F6, CH3CF3 (or CH2CF2 + HF at reduced pressures), plus substituted hydrazines, which mainly arise from addition of CF3 to the parent followed by combination of these radicals with CH3 or CF3. These fluorinated methyl hydrazine products detract from the general utility of CF3-N2-R compounds as sources for simultaneous study of the chemistry of CF3 and R radicals. At room temperature the hydrazine products accounted for more than 50% of the total yield; however, these products can be reduced by lowering the temperature and at 195°K their yields are negligible. The quantum yield for intramolecular (direct) formation of CH3CF3 + N2 was shown to be ≤0.002.
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  • 139
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    International Journal of Chemical Kinetics 6 (1974), S. 545-552 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The addition of propene to cyclohexa-1,3-diene has been studied between 512 and 638°K at pressures between 70 and 640 torr. The products are endo- and exo-5-methylbicyclo [2.2.2] oct-2-ene, and their formations are second order. The rate constants (in 1./mole-sec) are given by \documentclass{article}\pagestyle{empty}\begin{document}$$\log _{10} k_{{\rm endo}} = - (26070 \pm 80)/4.576T + (5.74 \pm 0.03)$$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$\log _{10} k_{{\rm exo}} = - (30090 \pm 80)/4.576T + (6.66 \pm 0.03)$$\end{document} The results are discussed in terms of a biradical mechanism.
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  • 140
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    International Journal of Chemical Kinetics 6 (1974), S. 725-739 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of ozone with simple olefins have been studied between 6 and 800 mtorr total pressure in a 220-m3 reactor. Rate constants for the removal of ozone by an excess of olefin in the presence of 150 mtorr oxygen were determined over the temperature range 280 to 360° K by continuous optical absorption measurements at 2537 Å. The technique was tested by measuring the rate constants k1 and k2 of the reactions (1) NO + O3 → NO2 + O2 and (2) NO2 + O3 rarr; NO3 + O2 which are known from the literature. The results for NO, NO2, C2H4, C3H6, 2-butene (mixture of the isomers), 1,3→butadiene, isobutene, and 1,1 -difluoro-ethylene are 1.7 × 10-1 4 (290°K), 3.24 × 10-17 (289°K), 1.2 × 10-1 4 exp (-4.95 ± 0.20/RT), 1.1 × 10-1 4 exp (-3.91 ± 0.20/RT), 0.94 × 10-1 4 exp ( -2.28 ± 0.15/RT), 5.45 ± 10-1 4 exp ( -5.33 ± 0.20/RT), 1.8 ×10-17 (283°K), and 8 × 10-20 cm3/molecule ·s(290°K). Productformation from the ozone-propylene reaction was studied by a mass spectrometric technique. The stoichiometry of the reaction is near unity in the presence of molecular oxygen.
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  • 141
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    International Journal of Chemical Kinetics 6 (1974), S. 773-776 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 142
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    International Journal of Chemical Kinetics 6 (1974), S. 801-811 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of added nucleophiles (methanol and 1,4-butanediol) on the steady-state kinetics of α-chymotryptic hydrolysis of a series of N-acetyl-L-amino acid methyl esters, R-CH(NHCOCH3)C(O)OCH3, has been studied. As a result, the rate and equilibrium constants of the ‘elementary’ steps of the enzyme process have been determined.It has also been demonstrated how the free energy-reaction coordinate profile changes if the structure (the size of the hydrocarbon chain) of the ‘chemically inert’ substrate fragment R is varied. The effects observed can be described by the following equation: where ΔGs and ΔGa are the free energies of formation of metastable intermediates, i.e., the enzyme-substrate complex and the acylenzyme, respectively, ΔG2≠ and ΔG3≠ are the free energies of activation for the chemical steps, i.e., enzyme acylation and acylenzyme hydrolysis, respectively; and ΔGtrans(R) is the free energy of transfer of substrate group R from water into a nonaqueous solvent.To explain the results obtained, a mechanism for enzyme-substrate interaction is suggested according to which the potential free energy of sorption of substrate group R on the enzyme is 2 ΔGtrans(R). Such a high gain in the free energy of hydrophobic interaction may only be realized if (a) in the free enzyme the sorption region has a thermodynamically unfavorable contact with the aqueous medium, and (b) water is forced out of the active center as a result of the hydrophobic interaction of substrate group R with the enzyme. Such a model is in agreement with the published x-ray data on the structure of the crystalline enzyme.The kinetic experiment has proved that not all the potential free energy of sorption is realized as binding force. Thus the true free energy of the binding of substrate group R with the protein does not exceed half the maximum value, both in the enzyme-substrate complex and acylenzyme.
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  • 143
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    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A step perturbation (concentration-jump or solvent-jump) relaxation method is described for studying the rates of fast reactions, using nontransient observation in a steadystate flow system. Therelaxation time is determined from a single measurement of an integrated relaxation amplitude. Remeasurement of the rate of dimerization of aqueous rhodamine B is reported.
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  • 144
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    International Journal of Chemical Kinetics 6 (1974), S. 753-761 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Shock tube experiments on the decay of OH-radical concentration after shock-initiated combustion of H2:O2:Ar = 10:1:89 mixtures were analyzed to give the rate constant 1 × 1015 cm6mol-2s-1for the reaction H + H + Ar = H2 + Ar overthe temperature range 1300 to 1700 K.
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  • 145
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    International Journal of Chemical Kinetics 6 (1974) 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 146
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chemically activated acetyl radicals, with an excitation energy of 78 kJ/mole, were formed by the addition of methyl radicals to carbon monoxide. At 273·K the pressure required to stabilize one half of the excited radicals was 500 torr. From measurements of the acetyl radical yield at pressures in the range of 700-2100 torr, and at temperatures in the range of 260-413 K, extrapolations to infinite pressure yielded kinetic parameters for the addition of methyl radicals to carbon monoxide, and for the thermal decomposition of acetyl radicals. The rate constants were found to be log k[cm3 / (mole·s)] = 11.2-25(kJ/mole/2.3) RT, and log k(s-1) = 13.5-72 (kJ/mole)/2.3RT, respectively. Estimated thermochemical properties of the acetyl radical are ΔHfº = -17 kJ/mole and Sº = 262 J/K°mole.
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  • 147
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    International Journal of Chemical Kinetics 6 (1974), S. 945-949 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 148
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    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Time-resolved measurements of the oxygen atom concentration during shock-wave initiated combustion of low-density (25 ≤ p ≤ 175 kPa) H2—O2—CO—CO2—Ar mixtures have been made by monitoring CO + O → CO2 + hv (3 to 4 eV) emission intensity, calibrated against partial equilibrium conditions attained promptly at H2:O2 = 1. Significant transient excursions (“spikes”) of [O] above constant-mole-number partial-equilibrium levels were found from 1400 to 2000°K for initial H2:O2 ratios of 16 and 10 and below ± 1780°K for H2:O2 = 6; they did not occur in this range for H2:O2 ± 4. Numerical treatment of the H2—O2—CO ignition mechanism for our conditions showed [O] to follow a steady-state trajectory governed by large production and consumption rates from the reactions with a pronounced maximum in the production term ka[H][O2]. The measured spike concentration data determine kb/ka = 3.6 ± 20%, independent of temperature over 1400 ≤ T ≤ 1900°K, which with well-established ka data yields \documentclass{article}\pagestyle{empty}\begin{document}$$k_{\rm b} {\rm = 2}{\rm .2 } \times 10^{14} \exp (- 57.5(kJ)/RT){\rm cm}^{\rm 3} /{\rm mole} \cdot {\rm s}$$\end{document} This result reinforces the higher of several recent combustion-temperature determinations, and its correlation with results below 1000°K produces a distinctly concave upward Arrhenius plot which is closely matched by BEBO transition state calculations.
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  • 149
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    International Journal of Chemical Kinetics 6 (1974), S. 29-37 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The following net processes occur in a system containing chlorine and hydrogen bromide: \documentclass{article}\pagestyle{empty}\begin{document}$$(1)\begin{array}{*{20}c} {} & {} \\ \end{array}{\rm Cl}_{\rm 2} + {\rm HB}r \to {\rm BrCl + HCl}$$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$(2)\begin{array}{*{20}c} {} & {} \\ \end{array}{\rm BrCl + HB}r \to {\rm Br}_{\rm 2} {\rm + HCl}$$\end{document} These reactions have been followed spectrophotometrically in a gas phase stopped flow apparatus. The first two reactions are strongly surface catalyzed on untreated glass or quartz, but are much slower if the cell surface has been covered with silicone and photochlorinated. Rates in such systems are first order in each reactant, and comparable limiting rate constants have been obtained in cells with different methods of preparing the surfaces and with different surface-to-volume ratios. These experimental rate constants must be equal to or greater than those of the homogeneous bimolecular reactions. Then limiting rate constants at 35°C in liters per mole per second are k1 ≤ 0.8, k 2 ≤ 15, and k3 ≤ 0.04. Reactions of HI with Cl2, Br2, and ICl are all much faster than reaction (2). These observations and those of other diatomic molecule reactions can be rationalized if halogen and hydrogen halide molecules react through a transition state in which the hydrogen atom is near the center of a triangle of three halogen atoms.
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  • 150
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    International Journal of Chemical Kinetics 6 (1974), S. 89-102 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Flash photolysis of 2,4,6-trinitrotoluene solutions (TNT) indicates a photochemically induced isomerization leading to the aci-quinoid isomer with an absorption maximum at 460 nm in nonpolar solvents, or the conjugate base of the aci-quinoid isomer with absorption maxima at 500, 540, and 630 nm in polar solvents. Both species, the quinoid isomer and the conjugate base, have transient existence and their identification was based on detailed spectroscopic and kinetic studies presented here. The magnitude of the negative charge on the transient conjugate base was determined with salt effect experiments and found to be equal to unity.
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  • 151
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    International Journal of Chemical Kinetics 6 (1974), S. 103-110 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the alkaline hydrolysis of five diol monoesters and related esters in aqueous DMSO, aqueous acetone, and aqueous ethanol are reported. A novel solvent dependency of the reactivity pattern of the various esters is noticed. The results are explained on the basis of an internal stabilization of the transition state and the influences of the various solvent systems on such transition states. It is suggested that such dipolar aprotic-protic solvent influences on reaction rates can be used as a criterion in the assessment of anchimeric assistance in such reactions.
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  • 152
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    International Journal of Chemical Kinetics 6 (1974), S. 111-123 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The exponential relaxation of CH3, produced by the reaction O + C2H4 → CH3 + HCO, to its steady-state concentration was quantitatively monitored after the reactants were mixed. The relaxation profiles yield the rate constant of the reaction O + CH3 → H2CO + H equal to (1.85 ± 0.28) × 10-10 cm3/molecule-sec at 300°K. Ancillary experiments yielded values for the rate constant for the reaction of O atoms with C2H4 at 300°K, the average of which is 7.7 × 10-12 cm3/molecule-sec. The experimental technique, which employs a fast-flow reactor coupled to a photoionization mass spectrometer, is described in detail and its potential discussed.
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  • 153
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    International Journal of Chemical Kinetics 6 (1974), S. 39-50 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the reaction between Mg2+ and Eriochrome-Black-T (EBT) has been investigated in the pH range between 7.05 and 9.0, in the presence of 12% ethanol. The reaction is found to consist of two parallel paths, one involving the tervalent unprotonated ligand, and one its monoprotonated form. The rate constant for the unprotonated ligand has a “normal” value, whereas that for the protonated form is much lower. The numerical value of the rate constant for the unprotonated ligand obtained from results at a magnesium concentration of 10-3M and a pH up to 9.0 is, however, inconsistent with that obtained from results at [Mg2+] = (1 to 4) × 10-3M and pH up to 8.1. This can be explained, at least partially, if we assume the intermediate MgHD to lose its proton not only to H2O, but also to other bases present in the solution.
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  • 154
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    International Journal of Chemical Kinetics 6 (1974), S. 279-290 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Oxidation of tetralin in the presence of tert-butyl hydroperoxide and tetralyl hydroperoxide, initiated with azobisisobutyronitrile, was studied at 60°C in order to examine the complications involved in the hydroperoxide method devised by Howard and Ingold. From literature data on absolute rate constants and our rates of oxidation, cross termination rate constants and contributions of each elementary propagation and termination step were computed. It was confirmed that this method was quite useful in determining the cross propagation rate constant, but it was also demonstrated that the rate of oxidation should be measured at very low conversion and with quite high concentrations of hydroperoxide, especially when the peroxy radical derived from the added hydroperoxide has a much lower termination rate constant than that from the oxidizing substrate.
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  • 155
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    International Journal of Chemical Kinetics 6 (1974), S. 51-59 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rate constants for the replacement of water from the inner-coordination shell of Co(NH3)5OH23+, I, by dimethyl sulfoxide (DMSO) as DMSO gradually replaced water in the solvation shell of I were found to approach, and finally equal, the water-exchange rate constant of I in aqueous media in accordance with expectation for a dissociative mechanism. Also the rate constants for the replacement of DMSO from the innercoordination shell of Co(NH3)5DMSO3+, II, by water as water replaced DMSO in the solvation shell of II were found to approach, and approximately equal, the DMSO-exchange rate constant for II in liquid DMSO in accordance with expectation for a dissociative mechanism.The DMSO-exchange rate constant for II in liquid DMSO was determined and found to be equal to (3.6 ± 0.8) × 10-4 sec-1 at 45°C.The dissociation quotient, [II] [NO3-]/[Co(NH3)5NO32+], was found to be equal to 0.28 ± 0.11 M at 45°C by NMR methods. The pseudo first-order rate constants for anation of II by NO3- and the solvation of Co(NH3)5NO3 2+ by DMSO were determined at various temperatures.
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  • 156
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    International Journal of Chemical Kinetics 6 (1974), S. 125-132 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photochemistry of p-fluoranil in dioxane was studied by electron spin resonance (ESR) and the ESR-rotating sector technique. The transient photoradical is identified as the p-tetrafluorobenzosemiquinone neutral radical with a hyperfine splitting of 1.1 gauss for the hydroxy proton and the fluorine hyperfine splittings of 3.8 and 14.1 gauss for the meta and ortho fluorines, respectively. The radicals decayed by self-disproportionation with a second-order rate constant at room temperature of approximately 3.2 × 109M-1s-1. The activation energy of the decay process is found to be about 2.4 ± 0.4 kcal/mole.
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  • 157
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    International Journal of Chemical Kinetics 6 (1974), S. 143-159 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The process of acetal hydrolysis is analyzed in terms of the competing steps of proton transfer and heavy atom reorganization. The results of this analysis are portrayed in a series of three-dimensional reaction coordinate diagrams. The observed pathway of hydrolysis (A-1, general acid catalyzed, or spontaneous) is shown to depend on the energy of the various possible intermediates in these reactions.
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  • 158
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    International Journal of Chemical Kinetics 6 (1974), S. 161-167 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: First-order rate constants for formation of cyclohexanone and 2-cyclohexen-1-ol from 1,2-epoxycyclohexane and 1,2-epoxycyclohexane-3,3,6,6-d4 have been determined over the temperature range of 677-746°K. The observed kinetic isotope effects are used in an attempt to determine the mechanism for formation of products. A distinction between a biradical and a concerted mechanism for the alcohol formation could not be made. However, if a common biradical is the precursor of both cyclohexanone and 2-cyclohexenl-ol then the rate of ring closure of this biradical must be much faster than the rates of hydrogen transfer to give the ketone and the alcohol.
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  • 159
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    International Journal of Chemical Kinetics 6 (1974), S. 229-244 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Translation-vibration (T-V) and vibration-vibration (V-V) energy transfer processes in the N2-CO2 system were investigated using classical trajectory techniques. Two empirical interaction potentials were employed. One is comprised of independent, atom-atom Morse-type functions operating between nonbonded atoms. The other included these atom-atom Morse functions plus Coulombic terms to account for the quadrupole-quadrupole intertion. Both interaction potentials led to similar T-V results. However, the result that CO2(v3) is excited ∼103 times more efficiently than N2(v = 1) was obtained, which is at variance with existing analytical theories of T-V energy transfer employing purely repulsive short-range potentials. Different V-V energy transfer probabilities were obtained from the two interaction potentials. The most important finding is that only when electrostatic orientation effects are combined with short-range repulsive interactions is the near-resonant \documentclass{article}\pagestyle{empty}\begin{document}$${\rm N}_{\rm 2} {\rm (}v = {\rm 1)} + {\rm CO}_{\rm 2} {\rm (000)} \to {\rm N}_{\rm 2} {\rm (}v = {\rm 0)} + {\rm CO}_{\rm 2} {\rm (001)}$$\end{document} V-V transfer found to be the dominant energy transfer path. This interaction potential also crudely accounts for the negative temperature dependence observed for this near-resonant V-V transfer at low temperatures (300-1000°K).
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  • 160
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    International Journal of Chemical Kinetics 6 (1974), S. 291-294 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Vibrationally excited pentyl-1, -2, and -3 radicals were formed selectively by the addition of thermal H atoms to the various pentene isomers with approximately 47 kcal/mole of vibrational energy. Decomposition products other than those expected, along with their pressure dependences, support the fact that either 1,2 or 1,3 hydrogen migrations with either a 3- or 4-member cyclic transition state is occurring with a ka of approximately 3 × 105 or 6 × 105 sec-1. A corresponding critical energy of 33 or 31 kcal/mole is found.
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  • 161
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    International Journal of Chemical Kinetics 6 (1974), S. 309-321 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The complexes PdCl42-, PdCl3(H2O)-, and PdCl3(Ac)2-, in rapid equilibrium with each other under the adopted experimental conditions, react with ethylenediamine according to the experimental rate law \documentclass{article}\pagestyle{empty}\begin{document}$$ k_{{\rm obs}} = \left\{ {\frac{k}{{\left[{{\rm H}^{\rm + } } \right]}} + \frac{{k'}}{{\left[{{\rm H}^{\rm + } } \right]\left[{{\rm Cl}^{\rm - } } \right]}} + \frac{{k''\left[{{\rm Ac}^{\rm - } } \right]}}{{\left[{{\rm H}^{\rm + } } \right]\left[{{\rm Cl}^{\rm - } } \right]}}} \right\}\left[{{\rm en}} \right]_{{\rm total}}$$\end{document} A reaction scheme is proposed involving the reaction of enH+ with each of the above species, and the specific rate constants are computed. The activation parameters are given.
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  • 162
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    International Journal of Chemical Kinetics 6 (1974), S. 359-370 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The four species in the title were decomposed under VLPP conditions at temperatures in the vicinity of 1100°K. Three model transition states were constructed that fit the low-pressure data thus obtained and that also yield (1) E298 = ΔE298; (2) E1100 = ΔE1100; (3) log A1100 = 16.4 per C-C bond broken. The predictions of these models as to values of the high-pressure rate constants for bond scission and the reverse rate constants (radical combination) are compared with existing data.
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  • 163
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    International Journal of Chemical Kinetics 6 (1974), S. 437-441 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rate constants of liquid-phase hydrogen abstraction by chlorine atoms from 1,2-C2H4Cl2 relative to those of addition to C2HCl3 and to C2Cl4 and to that of hydrogen abstraction from cyclohexane have been measured between 250 and 345°K. Assuming a zero activation energy for the addition reactions permits one to calculate the corresponding values for the liquid-phase hydrogen abstraction from the chlorinated ethanes. These values are discussed and compared with the gas-phase data.
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  • 164
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    International Journal of Chemical Kinetics 6 (1974), S. 617-630 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactions \documentclass{article}\pagestyle{empty}\begin{document}$$\begin{array}{*{20}c} {(1)} {{\rm O + HNO}_3 \to {\rm products}}\\ {(2)} {{\rm H + HNO}_{\rm 3} \to {\rm products}} \end{array}$$\end{document} have been studied in a discharge-flow system. Kinetic studies were made using resonance fluorescence for the measurement of atom concentrations. Based on the rates of atom loss, the following upper limits were obtained for the rate constants: \documentclass{article}\pagestyle{empty}\begin{document}$$ k_1 \le 3 \times 10^{ - 17} {\rm cm}^{\rm 3} /{\rm molec - sec} $$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$ k_1 \le 2 \times 10^{ - 15} {\rm cm}^{\rm 3} /{\rm molec - sec} $$\end{document} Observed reaction in the H—HNO3 system is at least partially due to an autocatalytic chain removal of both reactants. Diagnostic tests have suggested that OH, NO2, and NO3 are the chain carriers.
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  • 165
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    International Journal of Chemical Kinetics 6 (1974), S. 663-685 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the reversible reaction \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm H}_3 {\rm AsO}_3 + {\rm I}_{3^-} + {\rm H}_2 {\rm O}\rightleftharpoons{\rm H}_3 {\rm AsO}_4 + 2{\rm H}^+ + 3{\rm I}^- $$\end{document} have been studied spectrophotometrically in acid solution under conditions in which both the forward and reverse reactions go to virtual completionand in which the reaction comes to a practical equlibrium. The rates of theforward (Rf) and reverse (Rr) reactions are given by \documentclass{article}\pagestyle{empty}\begin{document}$$R_f = \{f + g/[\rm H^+] + h/[\rm H^+]^2\} [\rm H_3 {\rm AsO}_3][I_{3^-}]/[I^-]^2 $$ $$ R_r = \{u[\rm H^+] + \upsilon [\rm H^+]^2\} [{\rm H}_3 {AsO}_4][I^-] $$\end{document} where f, g, h, u, and v have the values (4 ± 1) × 10-5 mole/1.·s, (4.2 ± 0.2) × 10-5 mole2/1.2·s, (5.0 · 0.3) × 10-7 mole3/1.3·s, (1.1 ± 0.1) × 10-3 1.2/mole2·s, and (3.7 ± 0.2) × 10-3 1.3/mole3·s at 298.2°K and at an ionic strength of 2.00M maintained by adding sodium chloride. The stoichiometric equilibrium constant under similar conditions is 0.022 ± 0.003. Differentvalues of these parameters were obtained when sodium perchlorate and sodiumnitrate were used to control ionic strength.The results are compared with those from previous reports and a mechanism is proposed based upon an initial rapid equilibrium \documentclass{article}\pagestyle{empty}\begin{document}$${\rm H}_3 {\rm AsO}_3 + {\rm I}_2 \rightleftharpoons{\rm H}_3 {\rm AsO}_3 {\rm I}^ + + {\rm I}^ -$$\end{document} followed by a rate-determining attack of water upon H3AsO3I+, H2AsO3I, and HAsO3I-.
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  • 166
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    International Journal of Chemical Kinetics 6 (1974), S. 573-585 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A study has been made of the unimolecular decomposition of the vibrationally excited molecule CF2DCFH2*, formed from the combination of CF2D and CFH2 radicals. The α,β-elimination channels lead to the products cis- and trans-CFDCFH and CF2CH2 and H(D)F. The α,α-elimination channel produces cis and trans-CFHCFH and DF. The pressure dependencies of the various isomer ratios have been examined. For the α,α elimination the energy partitioning pattern is such that subsequent isomerization of the olefin product can occur. This, and previous work on CDCl2CH2Cl*, clearly show that the energy partitioning in α,α and α,β eliminations is very different. It is tentatively concluded that HF (from the CFH2 group) and HD eliminations also take place.
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  • 167
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    International Journal of Chemical Kinetics 6 (1974), S. 597-613 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rate of vibrational relaxation of HF(v = 1) by F atoms has been calculated using quasi-classical trajectory techniques. An attempt has been made to account for the effects of multiple potential energy surfaces on the vibrational relaxation efficiency within the electronically adiabatic assumption. Toward this end two potential energy surfaces were investigated. The LEPS equation was used to construct a reactive surface for F + HF′ → FH + F′ having a reaction barrier height of 5.4 kcal/mole, which is in agreement with a bond energy-bond order prediction. A nonreactive interaction potential consisting of atom-atom Morse functions was calibrated to Noble and Kortzeborn's [J. Chem. Phys. 52, 5375 (1970)] LCAO-MO-SCF results for FHF(2II). The results are in qualitative agreement with experiment. However, the nonreactive surface appears to be too repulsive, and consequently, the contribution of collisions on the nonreactive surface to the total vibrational relaxation rate coefficient are overestimated.
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  • 168
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    International Journal of Chemical Kinetics 6 (1974), S. 643-661 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electron transfer reactions of the superoxide ion with benzoquinone, trimethylbenzoquinone, and menadione in dimethylformamide were studied. A procedure of the determination of the relative rate constants of these reactions was developed; the reaction of O—2 with butyl bromide was chosen as a standard one. The relative rate constants measured at 20,°, 35°, and 50°C were slightly dependent on the quinone structure.The relationship between the free energy ΔF*of the electron transfer reactions and the standard free energy ΔFo was discussed. This relationship is proposed as ΔF* = αΔFo + β, where the proportionality coefficient α is equal to 0.04-0.11 for exothermal reactions and to 0.90-0.96 for endothermal reactions.
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  • 169
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    International Journal of Chemical Kinetics 6 (1974), S. 713-724 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rate constants and activation parameters are reported for the decarboxylation of malonic acid in seven normal alkanols (butanol-l to decanol-l inclusive). It is found that the enthalpy of activation of the reaction is a linear function of the number of carbon atoms in the hydrocarbon chain of tthe solvent, expressed by the equation: ΔH≠ = -600n + 30,000, where n is thenumber of carbon atoms in the chain. Also an equation is developed relatingthe rate constant for the decarboxylation of malonic acid in normal alkanols to n (the number of carbon atoms in the chain): log K = 10.854283 - 0.3212674n + (131.136876n - 6556.5438)/T + log T. With the aid of this equation rate constants may be calulated for the decarboxylationof malonic acid in any alcohol at any temperature which agree with experimental values to within the limit of error of the experiments. A comparison of the data obtained in the present research for the decarboxylation of malonic acid in normal alkanols with previously reported data for the reaction in amines indicates that for reaction taking place in alcohols the transition state probably contains two molecules of solvent but only one for the reaction in amines.
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  • 170
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    International Journal of Chemical Kinetics 6 (1974), S. 693-711 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A low-temperature matrix isolation method has been developed which makes possible the isolation and detection of HO2 radicalsfrom a gas-phase radical chain-reaction system containing atomic H, O and OH radicals as well. The formation of HO2 radicals is demonstrated in the rarified hydrogen flame. The same radicals are observed to exist during the slow oxidation reaction of hydrogen between the second and third inflammation limitsThe kinetics of accumulation of HO2, H2O2, and H2O has been studied as a function of total pressure, composition of reacting mixtures, temperature, and diameter and the treatmentof the surface of the reaction vessel. It has been established that in a reactor treated with boric acid, the concentration of HO2 radicalsis in the order of 101 2-101 4 particles/cm3. The kinetic relationship obtained confirms the necessity of including the following step in the mechanism of slow oxidation of hydrogen: \documentclass{article}\pagestyle{empty}\begin{document}$${\rm HO}_2 {\rm + }\;{\rm HO}_{{\rm 2 }} = {\rm H}_{\rm 2} {\rm O}_{\rm 2} {\rm + O}_{\rm 2} $$\end{document}For a quantitative description of the experimental results, calculationsof the complete mechanism of the slow reaction are performed by computer methods. The values of the rate constants of the elementary reactions that enter into the mechanism proposed were taken from published data. Some of them were varied by small intervals to give a better agreement with experimental values. The agreement justifies the mechanism proposed for the experimental conditions employed.
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  • 171
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    International Journal of Chemical Kinetics 6 (1974), S. 763-771 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The homogeneous pyrolysis of 2-butene subjected to shock heating was studied in the limit of high pressures by a relative rate technique. Over the temperature range of 1150-1325°K nearly equal amounts of methane, propylene, and butadiene were formed starting with either the cis- or trans-2-butene, while isomerization remained far from equilibrium. The results are consistent with a simple free radical mechanism for which we find \documentclass{article}\pagestyle{empty}\begin{document}$$ k^\infty [{\rm C}_4 {\rm H}_8 \mathop \rightarrow\limits_{cis} {\rm CH}_3 + {\rm C}_3{\rm H}_5] = 10^{16} \exp (-80,000/RT)\sec^{-1} $$\end{document} as the initial rate-limiting step.
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  • 172
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    International Journal of Chemical Kinetics 6 (1974), S. 787-800 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetic equations for an 81-reaction model of a photochemical smog chamber have been solved using a complete numerical integration as well as a quasi-steady-state approximation (QSSA) procedure. The two sets of results differ markedly in their prediction of experimentally significant factors such as the hydrocarbon depletion rate and the ozone and (NO)x peaking times. The sources of the discrepancy are traced to the fact that the assumed steady-state conditions were not satisfied, leading to errors in the concentrations of intermediate radicals which in turn affect critical rates in the reaction model.The occurrence of such discrepancies in various types of reaction models, and with different QSSA strategies, is discussed, and it is concluded that the extent of such errors in QSSA calculations cannot be reliably predicted. Their impact on conclusions regarding reaction mechanisms and rate constants can surpass uncertainties in experimental data; conversely the credibility of predictions derived through QSSA calculations becomes highly suspect. Since recently devloped methods for complete numerical integration of systems of kinetic equations are now available, it is recommended that these be adopted in future work, and that the use of QSSA be abandoned.
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  • 173
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    International Journal of Chemical Kinetics 6 (1974), S. 741-751 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Technical improvements have been made in the application of the phase shift method, recently developed and used in this laboratory to measure the absolute values of the rate constants of the reactions of O(3P) atoms with ethylene, propylene, 1-butene, and isobutene. More accurate rate constants have now been obtained for these olefins and themeasurements have been also extended to three additional olefins (cis-2-butene, trimethylethylene, and tetramethylene).The mean least squares values of the rate constants of the reactions of O(3P) with olefins at 26°C, expressed as k2 × 10-9 (1./mole2·sec), and their standard deviations are ethylene 0.43 ±0.05, propelene 2.02 ± 0.17, 1-butene 2.40 ± 0.32, isobutene 9.85 ± 1.34, cis-2-butene 9.00 ± 1.76, trimethylethylene 31.1 ± 3.0, and tetramethylethylene 44.4 ± 4.1. A Value of (5.78 ± 0.08) × 1010l.2/mole2·sec was obtained for the rate constant of the reaction O(3P) + NO + M, with M = N2O. Where comparison with the absolute rate constants in the literature is possible, agreement is very good, especiallywith some recent absolute values obtained by entirely different experimental techniques. Consistency with the relative rate constant of the O(3P) reactions with olefins previously determined in this laboratory, is excellent.
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  • 174
    ISSN: 1432-0568
    Keywords: Testicular peritubular cells ; Boar ; Postnatal development ; Ultrastructure ; Contractility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Die Membrana propria der Hodentubuli des Schweines zeigt einen deutlichen Schichtenbau: Auf die Basalmembran des Tubulusepithels (a) folgen eine nicht-celluläre Lage mit Kollagenfibrillen (b), die von einer inneren (c) und einer äußeren (e) Basalmembran umhüllten peritubulären Zellen (d) und dann das intertubuläre lockere Bindegewebe (f). Die ausdifferenzierten peritubulären Zellen haben viele morphologische Merkmale mit glatten Muskelzellen gemeinsam. So besitzen sie Plasmalemmeinbuchtungen in Form pinocytotischer Bläschen sowie eine große Anzahl von Filamenten mit einem Durchmesser von 60–70 Å, welche über elektronendichte Strukturen an der Innenseite des Plasmalemms befestigt sind. Ein Golgi-Apparat, rauhes endoplasmatisches Reticulum, Mitochondrien und Mikrotubuli bevorzugen eine kernnahe Position. Im Gegensatz zu den Verhältnissen bei anderen Species sind viele charakteristische Eigenschaften der peritubulären Zellen schon vor der Pubertät ausgebildet. Die Filamente können bereits am 4. Tag als feines Netzwerk beobachtet werden, sie erfahren am 25. Tag eine starke Vermehrung und sind von nun an regelmäßig orientiert. Auch andere Befunde sprechen dafür, daß die peritubulären Zellen um den 25. Tag eine gesteigerte Aktivität entfalten. Die histochemisch nachgewiesenen Konzentrationen von alkalischer Phosphatase, Adenosintriphosphatase und Glucose-6-phosphatase erreichen zu diesem Zeitpunkt die hohen Werte, die auch für die weitere Entwicklungsphase und die ausdifferenzierten peritubulären Zellen typisch sind. Pinocytotische Bläschen erscheinen in größerer Anzahl ab dem 97. Tag. Mit dem 140. Tag sind die peritubulären Zellen morphologisch ausdiffrenziert.
    Notes: Summary The boundary tissue of the porcine testicular seminiferous tubule (membrana propria) exhibits a distinct stratification: the basement lamina of the tubular epithelium (a) is followed by a non-cellular layer with collagen fibrils (b), the peritubular cells (d) with an inner (c) and outer (e) basement lamina and finally the intertubular loose connective tissue (f). Fully developed peritubular cells have many morphological features in common with smooth muscle cells, for instance inpocketings of the plasmalemma (pinocytotic vesicles) and a great number of filaments measuring 60–70 Å in diameter. These filaments are fixed at the inner side of the plasmalemma by means of electron-dense structures. The Golgi apparatus, rough endoplasmic reticulum, mitochondria and microtubules prefer a juxtanuclear position. In contrast that is seen in other species the porcine peritubular cells develop many of their characteristic features before puberty. In samples of the 4th day a fine network of filaments is already visible within the cytoplasm. These filaments are strongly augmented at the 25th day, and from now on they are arranged in a regular fashion. Other findings, also, underline an increased activity of the peritubular cells around day 25. At that time the concentrations of histochemically demonstrated alkaline phosphatase, adenosine triphosphatase and glucose-6-phosphatase reach the high levels typical for the stages of further development and the fully differentiated cells. Pinocytotic vesicles appear in great numbers from day 97. At the 140th day the morphology of the porcine peritubular cell is completely developed.
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  • 175
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    Anatomy and embryology 139 (1973), S. 319-336 
    ISSN: 1432-0568
    Keywords: Fetal thyroid ; Microfilaments ; Lysosomes ; Acid phosphatase ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The mesobranchial area and the median thyroid anlage of embryonic albino mice were investigated from the somite stage 4 to 40 (81/2–10 days of gestation). In stage I (5–25 somites), there is an unequal growth and differentiation of the epithelium in the floor of the pharynx, whereby a mesobranchial area with a stratified or pseudostratified epithelium is formed. This area is distinct from the remaining pharyngeal epithelium, among other things by an apical microfilament system in the superficial epithelial cells. It is found just basal to a row of plump cytoplasmic protrusions, which extend into the lumen of the pharynx. In stage II (26–40 somites), the cranial part (median thyroid anlage) of the mesobranchial area thickens in relation to the caudal part and grows down into the underlying mesenchyme. The filament system is concentrated in the superficial cell layer of the median thyroid anlage at the beginning of stage II and disappears during downgrowth. In both stages, but most pronounced in stage II, there is a population of 0.1–5 μ intracellular bodies, which occasionally contain the remains of organelles. The larger bodies, which often contain the remains of nuclei, are usually found peripherally while the smaller ones are more evenly distributed. Acid phosphatase can often be demonstrated histochemically in small bodies, while larger bodies are usually without reaction. Cells with pycnotic nuclei and/or degenerated cytoplasmic components are regularly found. Acid phosphatase can also be demonstrated in Golgi complexes and surrounding vesicles. Basal to the epithelium, bodies are occasionally found which may possibly have been extruded from that tissue.
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  • 176
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    Anatomy and embryology 141 (1973), S. 161-169 
    ISSN: 1432-0568
    Keywords: Rat ; Uterus ; Stroma ; Ultrastructure ; Sex steroids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of progesterone and oestrogen on the central uterine stroma has been examined in order to analyze what changes occur when the uterus is hormonally prepared for implantation. Both progesterone and oestrogen, when given separately, cause nucleolar enlargement and growth of the granular endoplasmic reticulum. However, after progesterone treatment the nuclei are large and spherical whereas they are spindle-shaped after oestrogen treatment. When oestrogen is administered to the progesterone-treated rat little change occurs in the stromal morphology. There is little morphological support to the view that oestrogen acts on the stroma to increase endometrial sensitivity. Further, progesterone seems to stimulate the synthesis of RNA and of cellular protein only in the stromal cell while oestrogen has a similar effect in all cell types of the uterus.
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  • 177
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    Anatomy and embryology 143 (1973), S. 95-114 
    ISSN: 1432-0568
    Keywords: Cleavage stages ; Blastocyst ; Pig ; Nucleus ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Ultrastructural observations of morphological changes in nuclei and cytoplasm of pig embryos during cleavage and early blastocyst stages are presented. Compact nuclear bodies (nucleosphaeridies) are demonstrable in the cleavage stages, and occasionally in the inner cell mass of blastocysts. The transformation of nucleosphaeridies leading to the formation of a peripheral network are usually found at the eight-cell stage. In morula, nucleoli make their first appearance as clearly distinguishable morphological entities. A marked disorganization of nuclear envelope is observed near to the cytoplasmic annulate lamellae (CAL) indicating a possible process of transformation of the former to the latter. During premorula stages cytoplasmic organelles (Golgi complex, endoplasmic reticulum, and CAL) are predominantly concentrated around the nucleus. CAL associated with fibrillogranular material similar to the material of the nucleoplasm occur in juxtanuclear positions. In the two-cell stage, degenerating paternal mitochondria are observed. In the morula the number of spherical mitochondria fell while that of elongated mitochondria increase. The trophoblast cells of the blastocyst stage contain cytoplasmic microfilaments which are closely associated with cell organelles, particularly the desmonsomes. Structurally changed mitochondria near the yolk globules and inclusion bodies of various morphology are found. A basal lamina is discernible parallel to the trophoblast layer facing the blastocoel. The observations are discussed in relation to physiological phenomena known to occur during embryogenesis.
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  • 178
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    Acta neuropathologica 25 (1973), S. 27-35 
    ISSN: 1432-0533
    Keywords: Ultrastructure ; Chordoma ; Sacrococcygeal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The ultrastructure of a sacrococcygeal chordoma is presented. The cells vary in their size and electron density but are thought to have a common origin. The nuclei presented prominent nucleoli and intranuclear bodies. Centrioles were seen in some of the cells. The rough endoplasmic reticulum was prominent and in most cells was very distended and corresponded to the intracellular vacuoles of light microscopy. The contents of the rough endoplasmic reticulum and the abundant extracellular substance were similar.
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  • 179
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    Acta neuropathologica 26 (1973), S. 285-299 
    ISSN: 1432-0533
    Keywords: Herpes simplex Virus ; Ultrastructure ; Viral Infection ; Virus-Host Interaction ; Nervous System
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The nervous system and small intestine of mice infected with herpes simplex virus were examined by electron microscopy from the viewpoint of virus-host interaction. The host cells examined included the neuron, astrocyte, oligodendrocyte, and Schwann cell. The susceptibility of the latter was not less than that of the neuron. The endothelial cell, perineural fibrocyte and smooth muscle cell were also host cells. Replication of herpes virus in the nervous system was proven to be identical to that occurringin vitro; initial reproduction of nucleocapsids in the nucleus and subsequent maturation at the nuclear membrane with envelope formation, followed by discharge into the cytoplasmic reticular cavities and finally release from the host cell. Inconsistency in the distribution of virus particles and viral antigen was chiefly concerned with the host cell nucleus and the glial cytoplasm. Herpes virions, though few, were identified in the axons of peripheral nerves, and in the periaxonal space of myelinated fibres in the brain and the nerve ganglia. Virions were present in tiny vesicles in the perikarya or as naked particles. In the distal parts of peripheral nerve, there was marked dissociation in the amount of virions between Schwann cells and the axon. The significance of the endoneural space and the axon in the neural speread of infection is discussed briefly.
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  • 180
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    Acta neuropathologica 24 (1973), S. 331-339 
    ISSN: 1432-0533
    Keywords: Diabetic Amyotrophy ; Muscle Biopsy ; Ultrastructure ; Type II Fibre Atrophy ; Partial Denervation ; Neurogenic Atrophy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Seven cases of diabetic amyotrophy were investigated by histochemistry and electron microscopy of biopsied muscles. Type II fibre atrophy of various grades was observed in the proximal atrophic muscles. Various changes of Z-band were observed in type II atrophic muscle fibres. In addition, mitochondrial changes, accumulation of glycogen, thickening of the capillary basement membrane and changes in the intramuscular nerves were also observed, both in the proximal and distal muscles. Some impaired motoneuron innervation of proximal muscles as well as distal muscles in a poorly controlled diabetic condition is suspected in “diabetic amyotrophy”.
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  • 181
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    Calcified tissue international 13 (1973), S. 83-92 
    ISSN: 1432-0827
    Keywords: Proteoglycan ; Collagen ; Cartilage ; Electron Microscopy ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé L'élimination de protéoglycans solubles de coupes de cartilage costal de boeuf, par extraction dans une solution de 4M d'hydrochlorure de guanidinium, permet de mettre en évidence des quantités abondantes de collagène dispersé et désagrégé dans la matrice. Les protéoglycanes, résistants à l'extraction, sont visibles sous forme de granules concentrés dans les régions périlacunaires. Les granulations plus importants des protéoglycanes semblent venir du chondrocyte. Dans la matrice, éloignée des chondrocytes, ces granules deviennent plus étroites. Un composant non granulaire “amorphe” masque les fibres de collagène, de telle sorte qu'elles sont difficilement visibles dans le cartilage intact.
    Abstract: Zusammenfassung Die löslichen Proteoglycane wurden mittels Extraktion in 4 M Guanidinhydrochlorid aus Rippenknorpelschnitten des Rindes entfernt. Dies erlaubte die Sichtbarmachung von großen Mengen von verstreuten und auseinandergerissenen Collagen in der Matrix. Die Protoglycane, welche sich nicht extrahieren lassen, erscheinen als kleine, in den perilacunären Regionen konzentrierte Körnchen. Die großen Proteoglycan-Körner scheinen in den Chondrocyten zu entstehen. Sobald sie sich in die Matrix, außerhalb der Chondrocyten, verlagern, werden die Körner kleiner. Ein nicht-granulärer, „amorpher” Bestandteil verhüllt die Collagenfasern, so daß diese im intakten Knorpel nicht deutlich gesehen werden können.
    Notes: Abstract Removal of the soluble proteoglycans from slices of bovine costal cartilage by extraction in 4 M guanidinium hydrochloride permitted the visualization of abundant amounts of dispersed and disaggregated collagen in the matrix. Proteoglycans which are resistant to extraction are seen as small granules which are concentrated in the perilacunar regions. Large proteoglycan granules appear to originate in the chondrocyte. As they come to occupy positions in the matrix distant from the chondrocyte, the granules become smaller. A non-granular, “amorphous” component masks the collagen fibers so that they cannot be readily seen in the intact cartilage.
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  • 182
    ISSN: 1432-1106
    Keywords: Ultrastructure ; Synapses ; Brain cortex ; Phospholipase A ; Membranes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of purified Naja nigricollis phospholipase A on slices from motor cortex from rat brain was analysed at an ultrastructural level. Samples stabilized directly with glutaraldehyde were compared with samples incubated in buffer with or without enzyme. Plasma membranes of nerve terminals, synaptic contact regions and synaptic vesicles were the main parameters studied. As judged by the electron microscopic technique the synaptic areas show a high resistance to the enzyme treatment. The intercellular space of the synaptic cleft seems unaltered. At the highest concentrations of the enzyme an increased density is noticed at the presynaptic part of the membrane. The extracellular space widens and nerve terminals and mitochondria become distended with increasing enzyme concentrations. The membranes all through the tissue appear ruptured to small pieces and at the highest enzyme concentrations used, altered in their structural organization. Quantitative analysis shows that the number of synaptic vesicles per unit surface area decreases, while ruptures of the plasma membranes of nerve terminals increase in number with increasing enzyme concentrations.
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  • 183
    ISSN: 1432-0878
    Keywords: Heart ; Rabbit ; Sinuatrial node ; Sinuatrial ring bundle ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The cells of the sinuatrial ring bundle are smaller than the ordinary myocardial cells; they have a regular outline and a large content of myofibrils exhibiting distinct H-bands and M-lines. Rudimentary T-tubules are found. The cells are connected by frequent nexus junctions, desmosomes and regions of interfibrillar contact, both on the well developed intercalated discs and at the periphery of the cells. The cells in the cauda of the sinus node, which extends alongside the crista terminalis together with the right branch of the sinuatrial ring bundle, are irregularly outlined and have a highly variable diameter (1–10 μm). They occur in clusters of closely packed cells. The content of myofibrils is sparse and the fibrils exhibit no M-lines and only weak H-bands. No T-tubules are found. The cells are not connected by intercalated discs and no nexus junctions are found. Both tissues contain unmyelinated nerves and nerve fibres. Varicosities with mitochondria and vesicles are found in close apposition to the muscle cells.
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  • 184
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    Cell & tissue research 136 (1973), S. 461-477 
    ISSN: 1432-0878
    Keywords: Neurohypophysis ; Acipenseridae ; Neurosecretion ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The neurohypophysis of sexually mature male and female Acipenser güldenstädti Brandt and Acipenser stellatus Pallas was studied light and electron microscopically. The recessus hypophysei lined with ependymal cells of two main types, “narrow” and “wide”, are in the center of the neurohypophysial “roots”. Processes from both cell types run radially to the basement membrane of the connective tissue layers abutting on the hypophysial intermediate lobe. Protrusions penetrating deep into the recessus hypophyseus are found in the apical parts of the “wide” cells. Pituicytes are rare in the neurohypophysis. The ultrastructure of both ependymal cell types and of the pituicytes is described. Nonmyelinated “Gomori-positive” (peptidergic) neurosecretory A1 and A2 type fibres and their terminals containing elementary neurosecretory granules (1400–1800 Å and 1000–1400 Å respectively) are the main structural elements of the neurohypophysis. Some “dark” and single myelinated neurosecretory fibres have been found. The adrenergic fibres (type B) were described earlier (Polenov et al., 1972a). The structural peculiarities of the neurohypophysis are discussed in functional and comparative-morphological terms.
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    Cell & tissue research 139 (1973), S. 567-582 
    ISSN: 1432-0878
    Keywords: Compound Eye ; Apis mellifica ; Polarized light ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung 1. Die Ausrichtung der Rhabdome ist in der Bienenretina nicht konstant. 2. Die Anordnung der exzentrischen Zellen in der Bienenretina ist ebenfalls nicht konstant, und es läßt sich keine symmetrische Verteilung dieser Zellen nachweisen. 3. Die Morphologie der Retina wird im Hinblick auf die Orientierung der Honigbiene nach dem Polarisationsmuster des vom blauen Himmel reflektierten Lichtes diskutiert.
    Notes: Summary 1. The orientation of the rhabdoms shows no regularity within the retina of the honeybee. 2. The arrangement of the eccentric cells is also irregular within the retina of the honeybee. 3. The morphology of the retina is discussed regarding the ability of the honeybees to orient according to the pattern of the polarization of light reflected from the blue sky.
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  • 186
    ISSN: 1432-0878
    Keywords: Touch receptors ; Sense organs ; Monogenean ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ventral surface of the posterior sucker of Entobdella soleae, a monogenean skin parasite of the sole Solea solea, is covered with more than 800 papillae ranging in size from 2.5–19 μm in diameter. The papillae are penetrated by nerves which double over themselves to form a stack-like array of lamellae running parallel to the surface of the haptor. No cilia or associated structures are present within these presumed sense organs and the papillae have no opening to the exterior. The much larger sucker papillae of a related species, E. hippoglossi, have been shown to have a similar ultrastructure. The possibility that the papillae may be contact receptors or strain receptors, providing proprioceptive information assisting the coordination of the attachment organ, is discussed and the papillae are compared with vertebrate touch receptors.
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    Cell & tissue research 138 (1973), S. 41-62 
    ISSN: 1432-0878
    Keywords: Germ cells ; Xenopus ; Spermatogenesis ; Chromatoid body ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The development of the male germ line in Xenopus laevis has been examined by electron microscopy. Findings have been compared to the parallel process in the female. Three structures unique to the germ line were found in both male and female cells: a fibrillar nuclear region free of DNA; largely proteinaceous masses of nuage material; and a chromatoid body. “Germ plasm” bodies of the egg and early embryo appear to represent a form of nuage material. The finding of a structure which can be identified as a chromatoid body in the female germ line is unique, as is its presence in sexually undifferentiated primordial germ cells. The chromatoid body in Xenopus, unlike that in mammals, does not persist in the spermatozoon. Instead, it dissociates into a series of coated vesicles during spermatogenesis. The chromosomal ultrastructure of meiotic prophase stages in Xenopus is similar in both sexes until diplotene, when male bivalents condense and enter meiotic metaphase instead of entering the extended lampbrush stage characteristic of the female. The multiple nucleoli present in gonia are lost at the onset of meiotic prophase, but no obvious mechanism for this process was observed.
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    Cell & tissue research 141 (1973), S. 319-330 
    ISSN: 1432-0878
    Keywords: Gonadal wall ; Holothuroidea (Leptosynapta clarki) ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The holothurian testes (as well as ovary) consists of three layers arranged concentrically around a central lumen which contains developing germ cells. The outer coelomic layer measuring 6 μ in thickness contains ciliated squamous epithelial cells, smooth muscle processes, nerve tracts, and occasional pigment cells. Interior to the outer layer is a haemal sinus measuring about 3 μ and consisting of haemal fluid composed of collagenous fibers and electron dense particles. Coelomocytes are embedded in this extracellular fluid matrix. The inner germinal layer, measuring 9 μ at the thickest regions consists of germinal cells, squamous epithelial cells, and coelomocytes. Occasional coelomocytes within the haemal sinus and germinal layer of the testicular wall contain spermatids enclosed within cytoplasmic vacuoles, suggesting phagocytosis as one of their cellular functions.
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  • 189
    ISSN: 1432-0878
    Keywords: Sympathetic ganglion ; Granule-containing cells ; Synapses ; Three-dimensional analysis ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The surface of 4 granule-containing cells, in a cluster within the rat superior cervical ganglion, was studied by a serial sampling technique for electron microscopy. The result shows that all the 4 cells receive one, or three afferent synaptic boutons from the preganglionic fibers impinging upon their somata, and a somatic efferent synapse exists at two locations on each soma of the 2 of these cells. The postsynaptic element of the efferent synapse is observed to be represented by non-vesiculated and vesiculated segments of dendrites, soma and a possible axon collateral of the adrenergic principal neuron of the ganglion. There is a remarkably constant development of the attachment plaque between the granule-containing cells themselves, representing 1.7–2.3% of surface area for each cell. The surface area exposed to the extracellular space (covered only by a basal lamina) varies from 0.1 to 2.3% of the total perikaryal surface of the 4 cells. A tendency is noted that those cells without efferent synapses possess a more extensive area exposed to extracellular space than those forming somatic efferent synapse to the postganglionic elements.
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    Cell & tissue research 141 (1973), S. 469-478 
    ISSN: 1432-0878
    Keywords: Microsporida ; Nosema apis ; Developing spore ; Freeze-etching ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The mature spore possesses a thick spore coat and a particle-bearing spore membrane. The highly laminated polaroplast membranes are located at the anterior pole of the spore. Close to its base, the polar filament is surrounded by the polaroplast membrane. The polar filament runs spirally towards the posterior pole of the spore. A large portion of the polar filament is arranged in two layers. A similar arrangement was also observed in immature spores and in the sporoblast stage, although it was not so orderly arranged in the latter. The developing polaroplast membrane was observed in the immature spore, but not in the sporoblast. The sporoblast wall is much thinner than the spore coat, but has the same texture. Endoplasmic reticulum is the most prominent cytoplasmic organelle in the developing stages of Nosema apis. Porous nuclear envelopes are also observed in developing stages. The role of the endoplasmic reticulum in the formation of the polar filament, polaroplast and spore coat, and the function of the spore membrane, are discussed.
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  • 191
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    Cell & tissue research 142 (1973), S. 89-102 
    ISSN: 1432-0878
    Keywords: Photoreceptors ; Larva ; Hemichordate ; Ultrastructure ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The eyespots of tornariae of enteropneusts (Ptychodera flava from Hawaiian waters and an unknown species from southern California) were studied by electron microscopy. An ocellus is composed of two types of cells: sensory and supportive. The former is characterized by a bulbous cilium (with 9+2 axoneme) at its distal end, one or sometimes two arrays of microvilli from its sides below the cilium, and a basal axon. The latter features large, clear vesicles which presumably contained the reddish-orange pigment seen in the ocellus of a living larva. Five-day old tornariae of P. flava are positively phototactic. Both cilium and microvilli may function as photoreceptors. The tornarian ocellus studied is compared with eyespots of other invertebrates, and the evolutionary significance of its putative photoreceptors is discussed.
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  • 192
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    Cell & tissue research 143 (1973), S. 107-116 
    ISSN: 1432-0878
    Keywords: Neurohypophysis ; Rat ; Pituicytes ; Organotypic culture ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Neural lobes of adult rats have been explanted and organ-cultured for 5–10 days. While perivascular cells and neurosecretory fibers undergo a progressive degeneration, scattered pituicyte-like cells are observed mostly associated with each other in number of two or three cells for group. Cultured pituicytes are quite similar to in vivo pituicytes except for some particular features as the shape of the nucleus and the number of dense bodies. Furthermore they share with the in vivo pituicytes the phagocytic capacity which appears even increased as far as neurosecretory fibers are concerned. Finally, degenerating pituicytes and free lipid droplets are observed in the intercellular spaces: the significance of these facts is discussed and tentatively interpreted. The organotypic culture of the neural lobe seems to represent an experimental model useful to obtain a relatively pure population of pituicytes.
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  • 193
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    Cell & tissue research 143 (1973), S. 117-133 
    ISSN: 1432-0878
    Keywords: Nervous system ; Ctenophores ; Intra-mesogleal nervous system ; Synapses ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Ultrastructural evidence is given of the occurrence of nervous elements in the mesoglea of Ctenophores based on the presence of the typical synapses of this phylum. In Beroids, nervous fibers from the ectodermal nerve-net cross the epithelial basal membrane and run through the mesoglea; they are devoid of any ensheathing cell. These neurites build highly differentiated synapses upon the muscles and upon peculiar cells, tentatively named mesenchymal cells. In Cydippids, nerve fibers and nerve cell-bodies have been observed in the mesoglea of the tentacles. The mesogleal core of each tentacle contains mesenchymal cells and a thick strand of neurons and neurites, forming a kind of elongated ganglion. Neurites of either the axial neurones or the epithelial nerve-net neurones form numerous radial nerve strands across the tentacular muscles. Interneural, neuro-muscular and neuro-mesenchymal junctions are very frequent in the tentacle. As far as the organization of the mesoglea is concerned, the Ctenophora thus appear closer to Turbellaria than to Cnidaria.
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  • 194
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    Cell & tissue research 143 (1973), S. 387-407 
    ISSN: 1432-0878
    Keywords: Oogenesis ; Urodela ; Yolk-formation ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Oogenesis was studied in adult Triturus vulgaris (Urodela) with the electron microscope. The oocytes investigated ranged between 50 μm and 1600 μm in diameter. Two types of yolk platelet formation were found. Since both types involve the incorporation of high numbers of pinocytotic vesicles they are believed to be of an extraoocytic origin. On the basis of the order of their appearance they were named primary and secondary yolk. Five different types of vesicles were found, which participate in a variety of activities, such as yolk formation and the formation of the Golgi apparatus. They originate from four different sources, namely the nuclear membrane, the cytoplasm in connection with ribosome-like particles, the Golgi apparatus and the plasma membrane through pinocytosis. The results obtained were discussed especially with respect to differences found between the anura and the urodela, such as the presence or absence of cortical granules or equivalent structures.
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  • 195
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    Keywords: Neurohypophysis ; Membranes ; Exocytosis ; Ultrastructure ; Freeze-fracturing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Posterior pituitary glands from normal rats, and rats which had been deprived of water for varying periods, were examined by the freeze-fracture method. This technique reveals large areas of the nerve cell membrane. Images consistent with exocytosis as the mechanism of release of the neurohypophysial hormones were observed. These modifications were most numerous after the rat had been starved of water for 2 days. In normal rats, the large number of neurosecretory granules within the nerve fibres caused a bulging of the nerve cell membrane. The “bulges” disappeared 2 days after removal of drinking water. Regions of the membrane displaying “bulges” were characterised by the absence of the typical membrane-associated particles. It is postulated that the close proximity of the neurosecretory granules to the nerve cell membrane may result in rapid fusion of the neurosecretory granules on stimulation of the gland. The change in properties of the nerve cell membrane overlying the neurosecretory granules, as suggested by the loss of membrane-associated particles, may represent a change in the structure of the membrane to a form which is more favourable for fusion.
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  • 196
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    Cell & tissue research 145 (1973), S. 213-227 
    ISSN: 1432-0878
    Keywords: Sensory pore ; Crustacea ; Natantia ; Chemoreceptor ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Résumé L'observation ultrastructurale du pore sensoriel de plusieurs espèces de Natantia révèle un complexe double. Un premier organe, le pore sensoriel principal, comprend une assise de cellules de soutien encadrant les parties distales de corps de cellules sensorielles. Ces cellules sensorielles portent des segments externes ciliaires qui se divisent dans une cavité sous-cuticulaire aplatie. En regard, la cuticule est amincie et comporte des micropores en forme de cratère et disposés par paires. A côté du pore sensoriel principal, un deuxième organe, le pore sensoriel latéral, est de taille plus réduite et est plus difficile à observer. Sous une invagination digitée de l'épicuticule, existe une cavité de forme complexe où s'épanouissent les segments externes ciliaires d'un faisceau de cellules sensorielles. Le pore sensoriel principal et le pore sensoriel latéral ont une ultrastructure de chémorécepteur.
    Notes: Summary Ultrastructural observation of the sensory pore of several species of Natantia reveals a twofold organ. A main sensory pore (M.S.P.) comprises a layer of supporting cells which encapsulate the terminal region of sensory cell bodies. These sensory cells include two ciliary processes dividing into a flat sub-cuticular cavity. The cuticle opposite is thin and perforated with crater-like paired micropores. Next to the main sensory pore, a second organ, the lateral sensory pore (L.S.P.), is smaller and more difficult to observe. A complex-shaped cavity underlies a contorted epicuticular invagination. Ciliary outer segments, belonging to a bundle of sensory cells, branch out in this cavity. M.S.P. and L.S.P. appear to be chemoreceptors.
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  • 197
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    Cell & tissue research 144 (1973), S. 435-452 
    ISSN: 1432-0878
    Keywords: Muscle spindles ; Intrafusal fibre types ; Development ; Deefferentation ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Muscle spindles of limb muscles were deefferented in neonatal rats by sectioning ventral roots or by removal of the lumbosacral spinal cord. Ten to 56 days after the operation, muscle spindles were examined in the medial gastrocnemius, extensor digitorum longus and soleus muscles. The differentiation of muscle spindles was not affected by deefferentation. The number of spindles in the investigated muscles was not reduced. Intrafusal fibres increased in number from two at birth to four per spindle on the average, as in normal muscles. The characteristic ultrastructural distinctions of nuclear bag and nuclear chain fibres developed as under normal conditions. However, intrafusal fibres atrophied slowly after fusimotor denervation, their polar zones becoming reduced in diameter by about 25% in comparison with control fibre diameters. Spindle capsules, on the other hand, increased in size and attained diameters comparable with normal spindles, appearing even somewhat distended. As intrafusal fibres degenerate after complete denervation at birth (Zelená, 1957), but differentiate in the absence of fusimotor innervation, it can be concluded that sensory nerve terminals induce and support their development. It is assumed that the morphogenetic influence of sensory terminals is mediated by release and uptake of a trophic substance at the synaptic junction. The occurrence of light and dense core vesicles in the sensory terminals and of coated invaginations and vesicles at both the axonal and plasma membrane speak in favour of such a possibility.
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  • 198
    ISSN: 1432-0878
    Keywords: Leydig cells ; Pekin Duck ; Testosterone ; Seasonal cycle ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Résumé L'ultrastructure des cellules de Leydig et des cellules de Sertoli du testicule du Canard Pékin a été étudiée au cours de la phase printanière du cycle sexuel, soit de janvier à juillet. Parallèlement on a effectué chez les mêemes animaux la recherche histochimique de la Δ5-3 β-hydroxystéroïdedeshydrogénase (Δ5-3 β-HSDH) ainsi que le dosage, par chromatographie en phase gazeuse des stéroïdes androgènes dans le plasma veineux périphérique et dans le testicule. Les cellules de Leydig du Canard possèdent les organites cytoplasmiques spécifiques des cellules stéroïdogènes (reticulum lisse, mitochondries à crêtes tubulaires) ainsi que d'autres structures souvent rencontrées dans ce type cellulaire (microfilaments, vacuoles, granules denses). Les cellules de Sertoli contiennent un reticulum agranulaire moins développé que celui des cellules de Leydig et, très rarement, des mitochondries à crêtes tubulaires. Ces divers organites cytoplasmiques subissent un cycle saisonnier. La différenciation du reticulum lisse et des crêtes mitochondriales tubulaires commence en janvier et atteint son optimum en mars. Leur régression s'amorce en avril; d'abord accompagnée de structures dégénératives transitoires; elle conduit à la dispartion totale de ces organites en mait. Aucun indice de nécrose n'est observé dans ces cellules. Histochimiquement, une activité Δ5-3 β-HSDH est présente dans les cellules de Leydig et, à un degré moindre, dans les tubes séminifères. Son intensité varie au cours du cycle. La confrontation de l'étude morphologique avec les résultats des dosages hormonaux montre qu'il existe une bonne corrélation entre le développement puis la régression du reticulum lisse et des crêtes tubulaires des mitochondries ainsi que des critères histochimiques de la Δ5-3 β-HSDH d'une part et l'évolution de la testostérone plasmatique et testiculaire d'autre part. De plus on observe une augmentation du rapport testostérone/Δ4-androstènedione testiculaire parallèlement au développement des organites cytoplasmiques. Ces organites semblent donc bien impliqués dans la synthèse et la sécrétion de la testostérone chez le Canard.
    Notes: Summary Leydig and Sertoli cells of the testis of the Pekin duck were studied ultrastructurally during the spring phase of the sexual cycle, from January to July. Simultaneously, in the same animals, Δ5-3 β-hydroxysteroiddehydrogenase (Δ5-3 β-HSDH) activity was ascertained histochemically and androgenic steroids of the plasma and testes were assayed by gas-liquid chromatography. The Leydig cells of the duck possess cytoplasmic organelles specific to steroidogenic cells (smooth reticulum, tubular mitochondria) as well as other structures often found in this cell type (microfilaments, vacuoles, denses bodies). The Sertoli cells contain an agranular reticulum that is less developed than that of the Leydig cells, and rarely show mitochondria with tubular cristae. These various cytoplasmic organelles undergo a seasonal cycle. The differentiation of the smooth reticulum and the mitochondrial tubular cristae begins in January and reaches a maximum in March. They begin to regress in April, at first with transitory degenerative structures, and then by total disappearance of these organelles by May. No indication of necrosis is observed in the cells. Histochemically Δ5-3 β-HSDH activity is present in the Leydig cells, and to a slightly lesser degree in the seminiferous tubules. The intensity varies during the cycle. The comparison of the results of the morphological study with the hormone assays shows that a good correlation exists with the development and regression of the smooth endoplasmic reticulum and tubular cristae in the mitochondria, as well as the histochemical criteria of the Δ5-3 β-HSDH on one hand, and the levels of plasma and testicular testosterone on the other hand. In addition there is an increase in the ratio of testicular testosterone to Δ4-androstenedione which parallels the development of the cytoplasmic organelles. These organelles thus seem to be implicated in the synthesis and secretion of testosterone in the duck.
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    Cell & tissue research 144 (1973), S. 453-466 
    ISSN: 1432-0878
    Keywords: Lacrimal gland ; Rat ; Duct system ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The duct system of the rat exorbital lacrimal gland consists of intercalated ducts, interlobular ducts and excretory ducts. The morphological changes from one type of duct to the next are gradual. At the light microscopical level this consists of a change from a bilaminar epithelium in the intercalated ducts to an epithelium, consisting of approximately three layers — which may be pseudostratified — in the excretory ducts. The basal layer of the intercalated ducts consists of myoepithelial cells, whereas the inner epithelial cells may have both a secretory and an electrolyte transporting function. The interlobular duct epithelium contains many cells with deep infoldings of the basolateral plasma membranes and associated mitochondria, suggesting a similar function to the striated duct epithelium in salivary glands. Numerous basal cells in this epithelium have tentatively been interpreted as unusual myoepithelial cells. Nerve terminals have been observed in the ductal epithelium.
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  • 200
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    Cell & tissue research 144 (1973), S. 475-487 
    ISSN: 1432-0878
    Keywords: Luteal cells ; Luteinization ; Endoplasmic reticulum ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Hyrax possess luteal cells with many ultrastructural features similar to those described in other mammalian species. The process of luteinization is gradual. Cells with increasing amounts of smooth endoplasmic reticulum become predominant in the developing gland. The luteal cells of Procavia and Heterohyrax show many ultrastructural similarities. In both species the corpus luteum persists throughout pregnancy.
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