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  • Electronic Resource  (145)
  • 1985-1989
  • 1970-1974  (145)
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  • 1974  (145)
  • Physical Chemistry  (81)
  • Life Sciences  (64)
  • 101
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    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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  • 102
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    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.
    Additional Material: 4 Ill.
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  • 103
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    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.
    Additional Material: 1 Tab.
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  • 104
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    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.
    Additional Material: 10 Tab.
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  • 105
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    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.
    Additional Material: 3 Ill.
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  • 106
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    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.
    Additional Material: 1 Ill.
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  • 107
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    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.
    Additional Material: 9 Ill.
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  • 108
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    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.
    Additional Material: 5 Ill.
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  • 109
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    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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  • 110
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    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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  • 111
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    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.
    Additional Material: 3 Ill.
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  • 112
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    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.
    Additional Material: 5 Ill.
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  • 113
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    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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  • 114
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    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.
    Additional Material: 3 Ill.
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  • 115
    ISSN: 0538-8066
    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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  • 116
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    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.
    Additional Material: 5 Ill.
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  • 117
    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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  • 118
    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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  • 119
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    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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  • 120
    ISSN: 0538-8066
    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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  • 121
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    New York, NY : Wiley-Blackwell
    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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  • 122
    Electronic Resource
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    New York, NY : Wiley-Blackwell
    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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  • 123
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    New York, NY : Wiley-Blackwell
    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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  • 124
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    New York, NY : Wiley-Blackwell
    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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  • 125
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    New York, NY : Wiley-Blackwell
    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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  • 126
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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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  • 127
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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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  • 128
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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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  • 129
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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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  • 130
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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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  • 131
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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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  • 132
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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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  • 133
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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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  • 134
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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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  • 135
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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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  • 136
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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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  • 137
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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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    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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  • 139
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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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  • 140
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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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  • 141
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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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  • 142
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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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    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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    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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    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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