Library

Notes: Study of the thermal decomposition of propane at very low conversions in the temperature range 760-830 K led to refinement of the mechanism of the reaction.The quotient VCH4 + C2H4/VH2 + C3H6 characterizing the two decomposition routes connected with the 1- and 2-propyl radicals proved to depend linearly on the initial propane concentration. This suggested the occurrence of intermolecular radical isomerization: in competition with decomposition of the 2-propyl radical: The linearity led to the conclusion that the selectivity of H-abstraction from the methyl and methylene groups by the methyl radical is practically the same as that by the H atom. The temperature-dependence of this selectivity ( μ = kCH3/kCH2) was given by\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm \mu = }\frac{{k_3 }}{{k_4 }} = \frac{{k_1 }}{{k_2 }} = 10^{0.26 \pm 0.03} \exp ( - 7.24 \pm 0.45{\rm kJ mol}^{{\rm - 1}} /RT). $$\end{document} Further evaluation of the dependence gave the Arrhenius representation \documentclass{article}\pagestyle{empty}\begin{document}$$ \frac{{k_7 }}{{k_6 }} = 10^{ - 5.97 \pm 0.03} \exp (115 \pm 5.1{\rm kJ mol}^{{\rm - 1}} /RT){\rm mol}^{{\rm - 1}} {\rm dm}^{\rm 3} $$\end{document} for the ratio of the rate coefficients of the above isomerization and decomposition reactions.Steady-state treatment resulted in the rate equation of the process, comparison of which with measurements gave further Arrhenius dependences.

Notes: Conditions of applicability of quasi-steady-state kinetic treatment have been investigated with respect to the explanation of the decomposition of propane and the influence of ethylene on this.From the measured rate of accumulation of ethane and from the relations between the kinetic equations describing product formation, the rate parameters of the initiation reactions were determined, for which the temperature-dependences \documentclass{article}\pagestyle{empty}\begin{document}$$ k_i = 10^{17,05 \pm 0.99} \exp ( - 356 \pm 11{\rm kJmol}^{{\rm - 1}} /RT)s^{ - 1} $$\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$$ k_{ie} = 10^{12.0 \pm 0.99} \exp ( - 225 \pm 15{\rm kJmol}^{{\rm - 1}} /RT){\rm mol}^{{\rm - 1}} {\rm dm}^{\rm 3} s^{ - 1} $$\end{document} were found.In the decomposition of propane under the examined conditions, the chain length exceeds 500. In response to ethylene the chain length significantly decreases, but even in this case the decomposition chains are long enough for it to be assumed that the ratios of radical concentrations are governed by the propagation steps.Calculations demonstrated that the actual radical concentration during a sufficiently short induction period approximates to the stationary concentration, so that it does not seriously affect the accuracy of the kinetic treatment.

Notes: The rate of decomposition of 2-pentoxy radical to acetaldehyde and n-propyl radical has been studied in the presence of NO in competition with nitrite formation at and above 200 kPa pressure over the temperature range of 363-413 K. The rate coefficient for the decomposition is given as log(kla/s-1) = (14.2 ± 0.4) - (13.8 ± 0.8) kcal mol-1/RT ln 10. Isomerization of 2-pentoxy radical by 1,5-hydrogen shift has been investigated in the range 279-385 K in competition with the decomposition in a static system, with methyl radicals present in high concentration to ensure trapping of the isomerized free radicals. The rate coefficient for isomerization is given as log(k3/s-1) = (11.1 ± 0.7) - (9.5 ± 1.1) kcal mol-1/RT ln 10. The implications of the results for atmospheric chemistry are discussed.

Notes: The thermal decomposition of butene-2-cis at low conversion and its effect on the pyrolysis of propane have been studied in the temperature range 779-812 K.It was established that 2-butene decomposes in a long-chain process, with the chain cycle \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm 2 - C}_{\rm 4} {\rm H}_{\rm 8} + {}^.{\rm CH}_{\rm 3} \to {}^.{\rm C}_{\rm 4} {\rm H}_{\rm 7} + {\rm CH}_{\rm 4} $$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm 2 - C}_{\rm 4} {\rm H}_{\rm 8} + {}^.{\rm CH}_{\rm 3} \to {}^.{\rm C}_{\rm 4} {\rm H}_{\rm 7} + {\rm CH}_{\rm 4} $$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm 2 - C}_{\rm 4} {\rm H}_{\rm 8} + {}^.{\rm CH}_{\rm 3} \to {}^.{\rm C}_{\rm 4} {\rm H}_{\rm 7} + {\rm CH}_{\rm 4} $$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$ {}^.{\rm C}_{\rm 4} {\rm H}_{\rm 7} \to {}^.{\rm H} + 1,3 - {\rm C}_{\rm 4} {\rm H}_{\rm 6} $$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm 2 - C}_{\rm 4} {\rm H}_{\rm 8} + {}^.{\rm H} \to {}^.{\rm C}_{\rm 4} {\rm H}_{\rm 7} + {\rm H}_{\rm 2} $$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$ \to 2 - {\rm \dot C}_{\rm 4} {\rm H}_{\rm 9} $$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm 2 - C}_{\rm 4} {\rm H}_{\rm 8} \to + 1,3 - {\rm C}_{\rm 3} {\rm H}_{\rm 6} + {\rm H}_{\rm 2} $$\end{document}(Besides the radical path, the molecular reaction can also play a role in the formation of the products.)The thermal decomposition of propane is considerably inhibited by 2-butene, which can be explained by the fact that the less reactive radicals formed in the reactions between the olefin and the chain-carrying radicals regenerate the chain cycle more slowly than the original radicals in the above chain cycle or in the reactions \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm C}_{\rm 3} {\rm H}_{\rm 8} + {}^.{\rm C}_{\rm 4} {\rm H}_{\rm 7} \to 1 - {\rm \dot C}_{\rm 3} {\rm H}_{\rm 7} + {\rm C}_{\rm 4} {\rm H}_{\rm 8} $$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$ \to 2 - {\rm \dot C}_{\rm 4} {\rm H}_{\rm 7} + {\rm C}_{\rm 3} {\rm H}_{\rm 8} $$\end{document}The reactions of the 2-propyl radical \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm 2 - \dot C}_{\rm 3} {\rm H}_{\rm 7} + 2 - {\rm C}_{\rm 4} {\rm H}_{\rm 8} \to {}^.{\rm C}_{\rm 4} {\rm H}_{\rm 7} + {\rm C}_{\rm 3} {\rm H}_{\rm 8} $$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$ \to 2 - {\rm \dot C}_{\rm 4} {\rm H}_{\rm 9} + {\rm C}_{\rm 3} {\rm H}_{\rm 6} $$\end{document} are further initiation steps. The ratios of the rate coefficients of the elementary steps of the decomposition (Table III) have been determined via the ratios of the products.Estimation of the radical concentrations indicated that only the methyl, 2-propyl and methylallyl radicals are of importance in the chain termination.On the basis of the inhibition-influenced curves, the role of the bimolecular initiation steps. \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm 2 - C}_{\rm 4} {\rm H}_{\rm 8} + {\rm C}_{\rm 3} {\rm H}_{\rm 8} \to {\rm \dot C}_{\rm 4} {\rm H}_{\rm 9} + {\rm \dot C}_{\rm 3} {\rm H}_{\rm 7} $$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm 2 - C}_{\rm 4} {\rm H}_{\rm 8} + 2 - {\rm C}_{\rm 4} {\rm H}_{\rm 8} \to {}^.{\rm C}_{\rm 4} {\rm H}_{\rm 9} + {\rm C}_{\rm 4} {\rm H}_{\rm 7} $$\end{document} could be clarified in the presence of 2-butene.

Notes: Experiments with propane-ethylene mixtures in the temperature range 760-830 K resulted in refinement of the role of ethylene inhibition in the decomposition of propane. The source of the rate-reducing effect of ethylene is the reaction This replaces the decomposition chains more slowly by means of the reactions than H-atoms do by direct H-abstraction from propane. Analysis of the ratios of the product formation rates showed that the selectivity of the ethyl radical for the abstraction of hydrogen of different bond strengths from propane was practically the same as that of the H-atom. The ratio of the rate constants of hydrogen addition to ethylene and methyl-hydrogen abstraction from propane by the H-atom (3) was determined \documentclass{article}\pagestyle{empty}\begin{document}$$ \frac{{k_3 }}{{k_8 }} = 10^{5.89 \pm 0.05} \exp ( - 30.8 \pm 1.1{\rm kJ mol}^{{\rm - 1}} /RT) $$\end{document} as was that of the decomposition and the similar H-abstraction of the ethyl radical \documentclass{article}\pagestyle{empty}\begin{document}$$ \frac{{k_3 }}{{k_8 }} = 10^{5.11 \pm 0.61} \exp ( - 129 \pm 10{\rm kJ mol}^{{\rm - 1}} /RT){\rm mol}^{{\rm - 1}} {\rm dm}^{\rm 3}. $$\end{document}Interpretation of the influence of ethylene required the completion of the mechanism with further initiation of the reaction besides termination via ethyl radicals.

Notes: The hydrogen abstraction reactions of tert-butoxyl with germane, phosphine, and trimethylsilane were studied by pyrolyzing di-t-butyl peroxide in the temperature range of 403 to 458 K. From the reported rate constant for the tert-butoxy radical decomposition in the literature, the absolute rate constants were determined from the study of competitive reaction between t-butoxy radical decomposition \documentclass{article}\pagestyle{empty}\begin{document}$$ (t - {\rm BuO }\;{\hbox to 45pt{\rightarrowfill}} {\hskip-42pt ^{{\rm decompose}}}{\hskip1em} {\rm CH}_{\rm 3} {\rm COCH}_{\rm 3} + {\rm CH}_{\rm 3}) $$\end{document} and hydrogen abstraction reaction. (t-BuO + RH → t-BuOH + R, where RH = GeH4, PH3, and HSiMe3)The Arrhenius parameters are found to be as follows: TextEa(kcal mol-1)Log A(1.mol-1s-1)t-BuO + SiHMe32.18.5t-BuO + GeH41.99.1t-BuO + PH31.49.0

Notes: Using a relative rate technique, rate constants for the gas-phase reactions of the OH radical with a series of monoterpenes have been determined in one atmosphere of air at 294 ± 1 K. Relative to a rate constant for the reaction of OH radicals with 2,3-dimethyl-2-butene of 1.12 × 10-10 cm3 molecule-1 sec-1, the rate constants obtained were (in units of 10-11 cm3 molecule-1 sec-1): α-Pinene, 5.45 ± 0.32; β-pinene, 7.95 ± 0.52; Δ3-carene, 8.70 ± 0.43; d-limonene, 16.9 ± 0.5; α-terpinene, 36.0 ± 4.0; γ-terpinene, 17.6 ± 1.8; α-phellandrene, 31.0 ± 7.1; myrcene, 21.3 ± 1.6; and ocimene (acis-, trans-mixture), 25.0 ± 1.9. These are the first quantitative kinetic data reported for many of these monoterpenes. The rate constants obtained are compared with the available literature data and with a priori estimates based on the number and configuration of substituents around the double bond(s). The tropospheric lifetimes of these monoterpenes with OH radicals, NO3 radicals and O3 are estimated and compared. Atmospheric lifetimes with respect to reaction with the OH radical are calculated to range from ∼0.75 hr for α-terpinene to ∼5 hr for α-pinene.

Notes: The kinetics of the oxidation of S2O32- by ClO2- have been studied in aqueous alkaline solution at 900C using classical titrimetric methods to follow the course of the reaction. The reaction takes place according to the stoichiometry S2O32- + 2ClO2- + 2OH- = 2SO42- + 2Cl- + H2O even in large S2O32- excess. There is some indication of a complex reaction pattern, but 70% of the ClO2- disappearance can be best described by the autocatalytic rate equation -d[ClO2-]/dt = k[S2O32-] [ClO2-] [H+] with k = (1.3 ± 0.2) ×108 M-2 sec-1. The mechanism is explained by postulating nucleophilic attack of S2O32- on HClO2 to form a chlorine-containing intermediate.

Notes: Conventional transition-state theory is used for extrapolating rate coefficients for reactions of O atoms with alkanes to temperatures above the range of experimental data. Expressions are developed for estimating structural properties of the activated complex necessary for calculating enthalpies and entropies of activation. Particular attention is given to the problem of the effect of the O atom adduct on the internal rotations in the activated complex. Differences between primary, secondary, and tertiary attack are discussed, and the validity of representing the activated complexes of all O + alkane reactions by a fixed set of vibrational frequencies and other internal modes is evaluated. Experimental data for reactions of O atoms with 15 different alkanes (CH4, C2H6, C3H8, C4H10, C5H12, C6H14, C7H16, C8H18, i-C4H10, (CH3)4C, (CH3)2CHCH(CH3)2, (CH3)3CC(CH3)3, c-C5H10, c-C6H12, c-C7H14) are reviewed.The following approximate expressions for ΔS

Notes: The hydrolysis kinetics of CICN have been reinvestigated from pH 0.0-10.5 and from 18-40°C. In the pH range from 1-5, the hydrolysis rate is invariant and the activation parameters (ΔH

Notes: The gas phase elimination of methyl 4-chlorobutyrate and methyl 5-chlorovalerate has been reexamined, in a static system and seasoned vessel, over the temperature range of 419.6-472.1°C and pressure range of 45-108 torr. The reactions, under maximum inhibition with propene, are homogeneous, unimolecular, and obey a first-order rate law. The rate coefficients are given by the following Arrhenius equations: for methyl 4-chlorobutyrate, log (k1(s-1) = (13.41 ± 0.60) - (226.8 ± 8.2) kJ/mol/2.303RT; and for methyl 5-chlorovalerate, log k1(s-1) = (13.20 ± 0.02) - (227.6 ± 0.3) kJ / mol / 2.303RT. The pyrolysis rates are found to be about a half of the rates reported in a previous work. As already advanced, the carbomethoxy substituent appears to provide anchimeric assistance in the elimination process, where normal dehydrochlorination and lactone formation arise from an intimate ion pair type mechanism. The partial rates towards each of these products have been determined and reported.

Notes: The rate constants of O2(1Δg) with aliphatic alcohols, terpenes, unsaturated hydrocarbons, chlorinated hydrocarbons, oxygen, and diamines have been studied in thepresence of NO2. The rate constants for oxygen, 1,2-ethane diamine, and 1,2-propane diamine are (9.9 ± 0.4) × 102, (8.7 ± 0.7) × 104, and (1.4 ± 0.3) × 104 1/mol/s, respectively. The rate constants for all other compounds are less than the oxygen rate constant.

Notes: The thermal reactions of endo- and exo-5-Y bicyclo[2.2.2]oct-2-enes (NYBO and XYBO) where Y = methyl, ethyl, and isopropyl have been studied in the gas phase between 567 and 695 K. For both isomers they are parallel first-order retro-Diels-Alder reactions with elimination of ethene (E) and monosubstituted ethene (YE).The observed Arrhenius parameters are used to discuss the mechanism and to estimate the heats of formation and the entropies of NYBO and XYBO. Group values are proposed for estimation of these thermochemical data for compounds of the same type by means of the methods of Benson.

Notes: Rate constants for overall H-atom abstraction by hydroxyl radicals from C—H and O—H bonds are estimated for alkanes, haloalkanes, aldehydes, ketones, ethers, alcohols, nitriles, and nitrates over thetemperature range 250-1000 K. These estimated rate constants utilize the modified Arrhenius expression K = A'T2e-E'/T in combination with the recommendations given in the recent review and evaluation of OH radical kinetics of Atkinson [1]. This estimation procedure gives good agreement, generally to within better than a factor of 2, of the estimated rate constants with theserecommendations.

Notes: The stopped-flow technique has been used to study the effect of cationic (CTAN), nonionic (Triton X-100), andanionic (SDS) micelles on the rate of the reaction between nickel(II) ion and the ligand pyridine-2-azo-p-dimethylaniline (PADA) at 20.0°C and ionic strength 0.03 mol dm-3. The complex formation reaction is markedly inhibited by both CTAN and Triton X-100 micelles. The kinetic dataare found to conform to a reaction mechanism which implies only partitioning of the ligand between water and the micellar phase, the estimated bindingconstant of PADA being significantly larger in the presence of CTAN aggregates. Anionic micelles strongly speed the complexation reaction, Which occurs in the micellar phase with the same rate and the same mechanism as in water. The extent of binding of PADA to anionic micelles is similar to that found for the cationic micellar aggregates.

Notes: The oxidation of primary alcohols by sodium N-chloroethylcarbamate in acid solution, results in the formation of corresponding aldehydes. The reaction is first order with respect to the oxidant and alcohol. The rate increases with an increase in acidity. The oxidation of α,α-dideuterioethanol exhibited a primary kinetic isotope, kH/kD = 2.11 at 298 K. The value of solvent isotope effect k(H2O)/k(D2O) = 2.23 at 298 K. Addition of ethyl carbamate does not affect the rate. (EtOC(OH)NHCl)+ has been postulated as the reactive species. Plots of (log k2 + Ho) against (Ho + log[H+]) are linear with the slope, φ, having values from 1.78-1.87. This suggested a proton abstraction by water in the rate-determining step. The rates of oxidation of alcohols bearing both electron-withdrawing and electron-donating groups are more than that of methanol. A concerted mechanism involving transfer of a hydride ion from the C—H bond of the alcohol tothe oxidant and removal of a proton from the O—H group by a water molecule has been proposed.

Notes: A theoretical treatment is given for fast, multiple bond-switching reactions, such as NO + NH2 → N2 + H2O. These reactions are characterized by all or most of the bonds being broken. The collision complex involved (whether long or short lived) is shown to be extremely anharmonic. Consideration of the master equation describing the competing processes of complex formation, internal rearrangement and collisional deactivation yields easily applied sufficient conditions for the recombination rate coefficient being independent of pressure.

Notes: Rates of disproportionation of 0.015-0.4 mM aqueous glyoxal toglycolic acid were measured at 0.24-75 mM NaOH and constant ionic strength, leading to the empirical rate expression r = (a1[OH-] + a2[OH-]2) [GT]/(1 + a3[OH-]), where [GT] is the total glyoxal concentration. These results were confirmed in bicarbonate/carbonate buffer and at 2-20 mM [GT]. The rate form is in contradiction to earlier work on glyoxal, which suggested a second-order dependence on [OH-], but agrees with the rate equation for phenylglyoxal disproportionation. The kinetic data can be explained by a mechanism postulating the presence of monohydrated and dihydrated forms of glyoxal in equilibrium, with the rate-limiting steps being intramolecular hydride ion transfers to the unhydrated carbonyl carbon of the mono- and divalent anions of glyoxal monohydrate.

Notes: The rate of decarbonylation of the hydroxyacetyl radical in acetonitrile is measured by effect modulated ESR spectroscopy and found to be log (KD/s-1) = (11.0 ± 1.5)-(2.3RT)-1 (37 ± 8)kJ/mol. The result is shown to be reasonably well connected with a variety of decarbonylation data known for other acyl species by asimple Evans-Polanyi relation.

Notes: Conditions leading to an explosive reaction of carbon monoxide and oxygen in the presence of small amounts of water have been examined at temperatures of 973 and 1048 K. Carbon monoxide and water were formed in the presence of oxygen by reaction with a thin film of carbon deposited on a quartz vessel. The carbon provided a reactive and reproducible surface, giving aconsistent rate of termination and thus allowing a quantitative descriptionof the conditions at the explosion in the region of the first limit. Calculations of the rates of the various branching and termination reactions at the onset of the explosion showed that the simple mechanism described earlier was still adequate to explain the reaction at temperatures up to 1050 K. From experiments with inert gases the transition from the first explosion limit to the region of the second explosion limit was demonstrated.

Notes: The thermal decomposition of diethyl ether was studied in the temperature range 697.2-760.5 K. The rate constant of reaction (1), and the ratio of the rate constant of reaction (2) to that of (12): were calculated from the amounts of products: \documentclass{article}\pagestyle{empty}\begin{document}$$ \log k_1 ({\rm s}^{{\rm - 1}}) = (17.2 \pm 0.6) - (82.4 \pm 2.0{\rm kcal mol}^{{\rm - 1}})/2.3RT $$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$ \log k_2 /k_{12^{1/2} } ({\rm dm}^{{\rm 3/2}} {\rm mol}^{{\rm - 1/2}}) = (4.1 \pm 0.4) - (11.9 \pm 1.3{\rm kcal mol}^{{\rm - 1}})/2.3RT $$\end{document}

Notes: The chromatographic retention of H and D atoms has been observed in a quartz tube using argon as a carrier gas for D and six different gases for H. The results give equilibrium constants for the reversible adsorption of H and D on quartz as well as the rates of desorption. Self-consistent conclusions can be drawn from the data. The adsorption energy appears to be ca. 50 kJ mol-1 indicating weak chemisorption. The observations are consistent with vibration frequencies on the surface of around 700-900 cm-1 for D. and around 1000-1300 cm-1 for H. It appears that only a fraction of the surface atoms (ca. 10-2) act as adsorption sites.

Notes: The bimolecular reactions in the title were measured behind shock waves by monitoring the O-atom production in COS—O2—Ar and CS2—O2—Ar mixtures over the temperature range between 1400 and 2200 K. A value of the rate constant for S + O2 → SO + O was evaluated to be (3.8 ± 0.7) × 1012 cm3 mol-1 s-1 between 1900 and 2200 K. This was connected with the data at lower temperatures to give an expression k2 = 1010.85 T0.52 cm3 mol-1 s-1 between 250 and 2200 K. An expression of the rate constant for CS2 + O2 → CS + SO2 was obtained to be k21 = 1012.0 exp(-32 kcal mol-1/RT) cm3 mol-1 s-1 with an error factor of 2 between 1500 and 2100 K.

Notes: The kinetics of the gas phase reaction between NO2 and CF2CCl2 has been investigated in the temperature range from 50 to 80°C. The reaction is homogeneous. Three products are formed: O2NCF2CCl2NO2 and equimolecular amounts of CINO and of O2NCF2C(O)Cl. The rate of consumption of the reactants is independent of the total pressure, the reaction products, and added inert gases and can be represented by a second-order reaction: \documentclass{article}\pagestyle{empty}\begin{document}$$ - \frac{{d[{\rm NO}_{\rm 2}]}}{{dt}} = - 2\frac{{d[{\rm CF}_{\rm 2} {\rm CCI}_{\rm 2}]}}{{dt}} = k[{\rm NO}_{\rm 2}][{\rm CF}_{\rm 2} {\rm CCI}_{\rm 2}] $$\end{document}However, the distribution of the products is influenced by the pressure of the present gases, which favor the formation of the dinitro-compound in a specific way. The effect of CF2CCl2 is the greatest. In the absence of added gases, the ratio of O2NCF2CCl2NO2 to that of O2NCF2C(O)Cl is proportional to (CF2CCl2 + γP products).The experimental results can be explaned by the following mechanism: P and X represent the products and the added gases: \documentclass{article}\pagestyle{empty}\begin{document}$$ - \frac{{d[{\rm NO}_{\rm 2}]}}{{dt}} = - 2\frac{{d[{\rm CF}_{\rm 2} {\rm CCI}_{\rm 2}]}}{{dt}} = k_1 [{\rm NO}_{\rm 2}][{\rm CF}_{\rm 2} {\rm CCI}_{\rm 2}] $$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$ k_1 = 3.16 \pm 0.5 \times 10^6 \exp ( - 10500 \pm 1000{\rm cal/}RT){\rm M}^{{\rm - 1}} {\rm s}^{{\rm - 1}} $$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm \gamma }_{{\rm CF}_{\rm 2} {\rm CCI}_{\rm 2} } :{\rm \gamma }_P :{\rm \gamma }_{{\rm C}_{\rm 2} {\rm F}_{\rm 5} {\rm CI}} :{\rm \gamma }_{{\rm CCL}_{\rm 3} } :{\rm \gamma }_{{\rm CF}_{\rm 4} } :{\rm \gamma }_{{\rm N}_{\rm 2} } = 1:0.22:0.15:0.14:0.054:0.015 $$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm \gamma }_{{\rm NO}_{\rm 2} } 〈 0.01 $$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$ k_3 = 1.4 \pm 0.3 \times 10^8 {\rm s}^{{\rm - 1}} $$\end{document}

Notes: Nascent product quantum state distributions have been measured for reactive, H + D2 → HD + D, and inelastic, H + D2 → D2

Notes: Translationally hot (3.7 eV center-of-mass collision energy) D atoms can be produced by the dissociative recombinationsof DCO+ ions with electrons in interstellar clouds. The reactions of hot D atoms with H2 molecules is an important factor in determining the D to H abundance ratio in the universe from observations of deuterated species in dense interstellar clouds. A simulation of this reaction has been carried out using exact quasiclassical reaction cross sections, together with a series of approximate total collision cross sections. It was found that the total probability of reaction, PR, at 3.7 eV was approximately 0.4. A reaction probability of this magnitude suggeststhat the loss of D atoms by the title reaction be considered in astrochemical modeling of deuterated molecules.

Notes: The kinetics of four gas-phase reactions involving halogenated methyl radicals (R = CF3, CF2Cl, CFCI2, and CCI3) with molecular chlorine have been studied using a tubular reactor coupled to a photoionization mass spectrometer. The radicals were homogeneously generated by the pulsed photolysis of precursor molecules at 193 nm. The subsequent decays of the radical concentration were monitored in real-time experiments as a function of Cl2 concentration to obtain the rate constants of these R + Cl2 reactions. Where possible, the rate constants were measured as a function of temperature to determine Arrhenius parameters. Apparent discrepancies between these measured rate constants for CF3 and CCl3 with Cl2 and ones obtained in prior indirect studies are explained. The higher activation energies for these R + Cl2 reactions compared to that of the CH3 + Cl2 reaction are attributed in part to the different polarities of the transition states formed.

Notes: We present calculations of the rate constants for the title reactions on a new accurate potential energy surface with a 9.65 kcal mol-1 barrier and a carefully fitted long-range attraction. The low-temperature thermal rate constant decreases from the previously calculated value, corresponding to a surface with a barrier of 9.80 kcal mol-1, which is opposite to the direction of change expectedbecause of the change in barrier height. This demonstrates the sensitivity of tunneling contributions to more global characteristics of the surface. The excited-state (n = 1) rate constants alsochange slightly, but not nearly enough to settle the controversial disagreement of theory with experiment for these rate constants.

Notes: The rate constant of the reaction between OH and OCS in helium over the temperature range 255-483 K has been determined using the discharge flow-resonance fluorescence technique. The OCS has been carefully purified to avoid interference from H2S and CO impurities. An FTIR with a multireflection cell was used to determine the impurity concentrations and the purified sample was found to contain less than 0.005% of H2S. At 300 K, the rate constant was determined to be (2.0 ±0.40.8) × 10-15 cm3 molecule-1 s-1. Although the rate constants showed slight positive deviation at lower temperatures, thev can be satisfactorily fitted by the Arrhenius equation, k = 1.13 × 10-13 exp(-1200/T) cm3 molecule-1 s-1. No pressure dependence was observed at all temperatures, nor was O2 enhancement observed under our experimental conditions.

Notes: The gas phase thermal isomerization of 4-acetyl-5-methyl-isoxazole affords 3-cyano-2,4-pentanedione as the only product in good agreement with previous proposed isomerization mechanism for isoxazoles. On the other hand, kinetic parameters and MO theoretical calculations do not agree with those previously reported. An alternative reaction mechanism which explains this fact is discussed.

Notes: The thermal decomposition of ethylbenzene has been investigated behind reflected shock waves over the temperature and pressure ranges of 1350-2080 K and 0.25-0.5 atm using a 1.6% C8H10 — Ne mixture. Major products of the pyrolysis are C7H8, C7H7, C6H6, C4H2, C2H4, C2H2, and CH4; C8H8 appears throughout the temperature range as a minor product. Comparison of the product profiles obtained by time-of-flight mass spectrometry and the results of model calculations strongly supports the initiation step of β C—C bond homolysis for C8H10 dissociation. A 51 kinetic step reaction mechanism with 24 species was formulated to model the temperature and time dependence of the major products observed in our experiments.

Notes: The present paper deals with the analysis of the amount of oxygen utilized for oxidation of a small dose of carbon substrate in carbon limited Brevibacterium flavum culture. The ratio of the measured oxygen consumption (mo2) to the amount of added carbon substrate (ms) gives a stoichiometric coefficient of the biological oxidation equation. A linear relationship between mo2 and ms was observed. To compare the efficiency of different carbon substrate utilization there has been introduced a normalized value β = mo2exp/mo2theor. There exists a simple relationship between β and the thermodynamical growth efficiency η The theoretical considerations are proved by experimental results with β, η and Yx/s in a chemostat culture at various medium flow rates.

Notes: The experiences in the production of CO2-incubators [1] have been the basis for the development of a system of gassing incubation cabinets, which, starting from a basic structure with temperature and humidity control (climatic test cabinets), consist of modular built up devices with regulating circuits for carbon dioxide and oxygen content of the incubation room atmosphere. The performance of the system is considerably extended by the equipment of the devices with a microcomputer system, by which the dynamic control of the parameters of the incubation room atmosphere is possible the first time.Essential mark of the system is further the standardized structural module for all devices and the flexibility in the equipment of the incubation room according to the demands of special tests.

Notes: Optimum conditions for autolysis of disintegrated cells of S. cerevisiae are at 50-53°C and pH 5.5; the process is terminated after 6 h. In the presence of sodium chloride (3-5%) the autolysis is complete after 5 h. The yield of autolysis of disintegrated yeast cells is about 70% of autolytic product per yeast dry weight. The product obtained after centrifugation, filtration and drying has very good sensoric and physical properties.

Notes: Reduction of (-)-menthone ((-)-1), (+)-(R)-methyl-α-campholenone ((+)-2), (+)-carvone ((+)-3), and eucarvone (4) was carried out by means of cells of the Rhodotorula mucilaginosa species immobilized in polyacrylamide gel. Alcohols with the (S)-configuration, (+)-neomenthol ((+)-1a), (+)-(R)-methyl-α-campholenol ((+)-2a), (-)-neoisodihydrocarveol ((-)-3a), dihydroeucarveol ((-)-4a), and small amounts of (-)-dihydroeucarvone ((-)-5), were obtained. The cells of R. mucilaginosa maintained after this reaction ability to reduce standard acetophenone to (-)-1-phenyl-1-ethanol.

Notes: The separation of xylanase from cellulolytic enzymes of A. terreus F-413 by affinity chromatography on xylan-containing supports was investigated. Xylanase purified over tenfold was obtained after column chromatography on xylan bound to controlled porous glass. The molecular weight of the purified enzyme has been found to be 140 000 daltons, and it is homogeneous in polyacrylamide gel electrophoresis. Purified xylanase also showed residual celluloytic activity (perhaps cross-specificity) with cellulosic substrates.

Notes: The maximum production of cellulose enzymes (FPactivity, CMcellulase and β-glucosidase) in the culture filtrate was observed at 27°C and pH 5.0, except for β-glucosidase, being at 6.0. The levels of extracellular enzymes in shake and stationary culture conditions was almost equal although they reached their maxima earlier in the former. The distribution of the three enzymes in extracellular, cytosol and cell debris fractions revealed most of the FPactivity and CMcellulase occurring extracellulary. More than 50% of the β-glucosidase was present in the cell debris fraction.

Notes: A simple method for the investigation of the water transport velocity in cereal kernel is described. The mechanism of the water transport is discussed. It is explained that data, place and strength of the effect of hydrolytic enzymes can be determined on the basis of the changed transport resistance from the temporal change of the different diffusion coefficient. The fundamentals of the modelling of steeping processes are given.

Notes: For ensiling of herbage which is rich in protein and therefore difficult to ferment a procedure is proposed. It is based on aerobic acidification using biological deoxydants. The crops are treated with a suspension of living cells of Acetobacter methanolicus and a water solution of ethanol. This treatment brings about environmental conditions which promote lactic acid fermentation: anaerobiosis, complex nutritional supply and protective concentrations of H+-ions. Preliminary attempts have confirmed the principle of conservation by aerobic acidification combined with biological deoxydation in agricultural practice. Damages of legume crops with high protein content are prevented. The advantages of the new ensiling process is discussed in comparison to traditional treatment.

Notes: A dry white wine with an alcoholic content of 10 to 14% v/v was produced by yeast fermentation of slurried ground soybeans, soybean milk and whey from tofu production. Wines from whey and soybean milk were judged by a 20 member taste panel to be acceptable and comparable to a commercial chablis control. Chemical analysis indicated that the high fat and protein contents of soybeans do not cause a problem in the production of wines from soybeans as the lipids and proteins are precipitated by the acid and alcohol formed during the fermentation. The less recovered following fermentation were dehydrated and ground to a flour having an enriched protein content due to the yeasts and an improved flavor resulting from the yeast fermentation.

Notes: The overflow production of metabolites appears to be an energy spilling process in terms of life because part of the energy of the primary substrate remains in the metabolite produced. The other part of energy, which is liberated as reducing equivalents and/or ATP along the way to the product, must be wasted. This part is discussed to be responsible for the discrepancies between the theoretically possible and experimentally obtained product yields, because for the wasting process substrate or product are consumed. By reducing the amount of this superfluous energy the product yield should be increased. The auxiliary substrate concept occurs to be an appropriate method.

Notes: By using particle electrophoresis and quantitative analysis the interaction of anionic surfactants (sodium dodecylculfate, sodium decylbenzene sulfonate) with a hydrocarbon-grown yeast and a commercial baker's yeast has been investigated to obtain further informations about the chemical composition of the surface region (3-6 nm) of the cell wall of this yeasts. A correlation is found between the chemical composition and the different adsorption behaviour of various batches of the same yeasts. It was found that surface-localized hydrophobic glycoproteins, probably proteophosphomannan are responsible for the strong pH dependent adsorption behaviour of a typical Candida species.In contrast the cell surface of a typical Saccharomyces species was strongly hydrophilic and showed no surfactant adsorption.This can be explained by the presence of a polysaccharide probably phosphomannan in the surface region only.The implication of proteins in the adsorption process is confirmed by model experiments too.The models for the yeast cell wall proposed by LAMPEN and KIDBY et al. were critically discussed in terms of our results.

Notes: Finely ground ore material (90%-200 mesh) was subjected to acid microbiological leaching in 20% and 30% (wt/vol) suspensions. The rate of aeration was maintained at 2 and 4 1/min · 1. After the onset of the microbiological phase of leaching, the solubilization of iron was initially rapid but was succeeded by Fe(III) precipitation. Major differences were apparent between inoculated and uninoculated suspensions for each metal analyzed (Fe, Al, Co, Cu, Ni, Zn). The sulfur balance in leach residues indicated elevated levels of elemental S and sulfate in the inoculated systems.

Notes: The ethanol tolerance behaviour of the strain Saccharomyces cerevisiae Sc 5 regarding the growth is characterized by a threshold ethanol inhibitory concentration (P1' = 42.5 g/l) and a linear relationship between the specific growth rate and the ethanol concentration within the limits P1' 〈 P 〈 P′. The maximum ethanol concentration for growth amounts to P′ = 84 g/l.A general model for the inhibition of growth and alcohol production, respectively, caused by ethanol, is deduced from experimental and bibliographical data: \documentclass{article}\pagestyle{empty}\begin{document}$$\begin{array}{l} \mu = \mu_0 - {\rm a}'(P - {P_{1}}^{\prime})^{{\rm b}'}, \\ \nu = \nu_0 - {\rm a}(P - P_1 )^{\rm b}.\end{array}$$\end{document}If the inhibitory effects are linear, the exponents b, b' become 1.

Notes: Industrially acceptable production of ergot alkaloids in surface culture under sterile conditions is described. After elucidation of the biochemical and morphological differentiation in the production microorganisms it is possible to elaborate a relatively simple cultivation method with good yields. Surface cultivation is especially advantageous for the production of spores in large quantities which are used as inoculum in industrial fermentations or as infection material (field production of ergot alkaloids, mycoinsecticides).

Notes: L-Lysine decarboxylase (LL-Lysine carboxylase E.C. 4.1.1.18) is produced by a strain of the genus Klebsiella.The bacterial cells are cultivated at a temperature of 37°C with and without shaking. The production of LL-Lysine decarboxylase is increased by adding of LL-Lysine to the medium. At the end of cultivation the cells are killed by thymol, washed in water and dried by means of acetone and ether.Compared with specimen derived from other bacteria the LL-Lysine decarboxylase in the shape of dried cells shows a high specific activity. The preparations are free of disturbing enzyme activities, have a high level of stability and may be used for determining of LL-Lysine by means of enzyme electrodes.

Notes: Under the conditions of continuous cultivation studies were carried out on a mixed culture (association) with two strains of yeasts: Candida sp., assimilating animal fats, and Candida scottii, assimilating reducing sugars. A complex nutrient medium of wood hydrolysate was used.It was established that in this medium, at a rate of dilution of D = 0.25 h-1, the mixed culture assimilates the fats and the sugars simultaneously. As a result of this the yield of absolutely dry yeasts with regard to the total sum of fats and sugars amounts to 71% in the case of incineration fat and to 82% in the case of technical pork fat.The contents of protein, amino acids, lipids and ashy substances in the yeasts obtained from a medium with fats do not differ substantially from those obtained from the same medium without fats.

Notes: In the customary technique will be used a fusion chamber with an inhomogeneous electric field. The disadvantage is that the fusion conditions are not constant in the chamber. Yet for di-electrophoretic collection of the cells their own field-inhomogenizing influence is sufficient that is, the electrofusion can proceed also in very simple chambers with homogeneous fields.

Notes: DNA clones representing two subfamilies A and B of legum in genes and a recombinant phage containing a complete legumin B gene have been isolated and characterized by DNA sequencing. A DNA fragment harbouring the legumin B gene and adjacent sequences was used for Ti-mediated transfer into tobacco cells.

Notes: A batch fermentation is modelled with constant and variable yeild terms. It is shown that the model cannot exhibit oscillations if a constant yield term is used. Oscillations in the cell concentration, but not in the limiting substrate concentration, can be simulated if a variable yield function of the limiting substrate is used. Conditions, for which the variable yield needs to satisfy in order to generate oscillations in the cell concentration, are discussed. The primary condition is that the yield must become zero at the same time that the specific growth rate does. Experimental results exhibiting oscillatory behavior are presented and compared with the proposed model.

Notes: The production costs of ethanol are dependent on the efficiency of the substrate-ethanol conversion to a high degree. The more the substrate used during the fermentation is converted into alcohol the better is the economy of the process.Therefore the ethanol yield Y SP is an important object of the process optimization.In batch fermentation processes the most essential influence factors are the initial biomass concentration X0, the initial substrate concentration S0, the temperature T, and the pH-value.A model reflecting the complex relationships between these influence factors and the ethanol yield could be obtained by regression. It allows an exact valuation of these optimum process parameters which are necessary for realizing high ethanol yields in the batch fermentation.For the strain Saccharomyces cerevisiae Sc 5 used in this research was found an ethanol yield maximum YSP = 0·5384 at the parameters X0 = 64.61 g/l S0 = 82.91 g/l T = 36.45°C pH = 6.54.

Notes: The determination of oxygen diffusion coefficients was carried out by a modified chronoamperometric method using a stationary platinum electrode.The determined diffusion coefficients are related to approximated η0-values.It was shown a relation of Di and η0 according to the HAYDUK-CHENG-potential equation.That means a strong relative lowering of oxygen diffusion coefficients already by low viscosities, but a little influence at high viscosities.A simple laboratory thin film reactor is described, in which the oxygen supply is maintained by diffusion. This reactor is suitable very well for fermentations of viscous fluids.

Notes: Using a system analysis for the investigation of all processes which occur in a biochemical reactor on the micro and macro level, a mathematical model was worked out. It characterizes the model of the kinetics and stoichiometry of the growth of microorganisms and the rules of hydrodynamics and mass transfer in form of blocks. Relating to the discussed mathematical total model [11], experimental data on which the calculation of the model parameters is based are described in this second part of the paper. They were determined not only directly from the cultivation process, but also from experiments with model media.

Notes: Upon sterilization, freeze-dried kefir grains are to be supplemented with yeast preparation, yeast showing the lowest survival in the course of freeze drying.A mixture of 20% sucrose solution and starch appeared to be the most efficient dispersing agent to protect yeast in the freeze-drying process.A starter which is produced with the kefir starter culture, does not differ in its microbiological, biochemical and organoleptic properties from a starter as obtained with kefir grains in the same time, such starter shows a better consistency.The preparation of such starters is less laborious and less complicated than the preparation of starters using kefir grains.

Notes: The dynamics of pH-controlled chemostat and pH-auxostat is considered. The medium flow governed by pH-controller is calculated using the ionic (mass-charge) balance equations. The generalized equations of pH-controlled continuous fermentation are developed for the case of two variables: cell biomass and residual substrate concentrations. The study of steady state solutions has shown a substantial dependence of the variable patterns on a concentration of alkali (or acid) in titrant medium flow. The generalized analytical expressions for eigenvalues (reciprocals of transient characteristic times) of the culture dynamics have been obtained. The rates of transients during the steady state establishment are considered using these eigenvalues.

Notes: By comparing different activity data of the buffered cellulase solution before and after contact with the substrate the interaction between Penicillium janthinellum cellulase and wheat straw, resp. its components (holocellulose and isolated lignin) has been investigated. The loss of activity due to sorption or denaturation has been found to differ widely between the different activity data and between the various substrates. A remarkable loss of enzyme activity was observed after contact with isolated straw lignin. The differences in activity decrease between the cellulose and the lignin moiety were found to be largent with the cellobiase activity.

Notes: The protein enrichment of citrus dried peel on solid-state fermentation by Aspergillus niger in packed bed column was optimized using a two factor central composit design with α = 2 considering the “initial moisture content of the fermentation mass” and the “temperature in the centre of the fermenter”. It results significance for the moisture content (optimum 56%) and non significance for the temperature in the conditions employed. This indicates that a considerable range of temperature increase for the investigated SSF system could be allowed.

Notes: Glucose dehydrogenase (E.C. 1.1.1.47) from B. megaterium M 1286 was immobilized together with mutarotase (E.C. 5.1.3.3) on several organic carriers and by different methods. The storage stability of the enzyme at pH-values 〉 6 is slightly improved by immobilization and the pH-optimum is shifted from 8.3 to 8.0. Kinetic constants of the immobilized enzyme are: K′M(NAD+) = 5.36 × 10-4 mol/l K′M(glucose) = 3.76 · 10-2 mol/l and V′max = 5.54 · 10-5 mol/(l min g carrier) for the most active preparation (2.16 mg enzyme/g carrier).In reactor experiments the immobilized glucose dehydrogenase was used with glucose to regenerate NADPH in NADPH-dependent iron-III-protoporphyrin-IX-imidazole catalyzed hydroxylation and demethylation of model substrates of cytochrome P-450.The advantages of the coupling of both reactions with cofactor recycling are shown and discussed.

Notes: Mixtures of acetone/water (93 : 7 ··· 90 : 10, v/v) are favoured solvents for the extraction of ubiquinone-10 from Acetobacter methanolicus IMET B 346. Using these solvent mixtures ubiquinone-10 was extracted nearly completely. Other lipids were extracted partially. Extracts were obtained by optimal conditions with a ubiquinone content 〉 5%.

Notes: The uptake of cadmium ions from an aqueous solution by living, resting, and dead biomasses was investigated. The dependence of the uptaked amounts on pH-value of the medium, temperature and concentration of cadmium ions is demonstrated as well as the rate of uptake.Maximum realisable concentrations were 12 mg/g biomass in living cells and about 20 mg/g biomass in resting or dead cells, respectively.

Notes: The kinetics of the hydrolysis of microcrystalline cellulose (MC) by a Trichoderma reesei cellulase complex and by the individual endoglucanase (pI 4.4-5.2) and cellobiohydrolase (pI 4.0-4.2) has been studied. A flow chart for the enzymatic hydrolysis of the cellulose has been revealed, which formed a basis for a computer simulation of the kinetic regularities observed. As a result of it, the values of the catalytic rate constants for the individual stages of the enzymatic degradation of MC have been calculated. Then, the synergistic behaviour of endoglucanase and cellobiohydrolase in the hydrolysis of MC has been described both quantitatively and graphically. The relative efficiency of the individual stages for the MC hydrolysis in terms of glucose and cellobiose formation for cellulase complexes of various composition has been calculated. It was quantitatively shown that cellobiohydrolase plays the key role in the MC hydrolysis by T. reesei cellulase preparations, because it gives up to 80% glucose and up to 80-90% cellobiose in the presnce of endoglucanase which in turn plays a relatively minor role in a direct formation of both soluble products of the hydrolysis.

Notes: Genomic RNA of the Respiratory syntical virus (RS-virus) was used as a template to synthesize calfthymus DNA-primed cDNAs. These cDNAs were subsequently cloned into the E. coli plasmid pBR 322 at the PstI-site. By hybridization 6 recombinants with virusspecific cDNAs representing 10% of the whole genome could be isolated.