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  • 1
    Electronic Resource
    Electronic Resource
    Theoretical study of the thermal isomerization of fulvene to benzene (1996)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 9 (1996), S. 801-810 
    Details
    ISSN: 0894-3230
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The potential energy surface for the thermal isomerization of fulvene to benzene was studied by modified Gaussian-2 (G2M) and the bond additivity-corrected fourth-order perturbation Møller-Plesset (BAC-MP4) methods. Three isomerization pathways were investigated. One involves the intermediate prefulvene by a concerted mechanism, which has a significantly higher barrier. The second, also involving prefulvene and cyclopenta-1,3-dienylcarbene intermediates, has a barrier of 84·0 kcal mol-1. The third, a multi-step pathway, includes bicyclo[3.1.0]hexa-1,3-diene and cyclohexadiene carbene intermediates. The activation energy of the multi-step pathway was calculated to be 74·3 kcal mol-1, which is 7-11 kcal mol-1 higher than the experimental value obtained by a brief very low-pressure pyrolysis (VLPP) study. RRKM calculations were performed on the multi-step pathway in order to determine the rate of isomerization. These theoretical results cast doubt on the validity of the VLPP data. © 1996 John Wiley & Sons, Ltd.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Theoretical study of reactions of N2O with NO and OH radicals (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 28 (1996), S. 693-703 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactions of N2O with NO and OH radicals have been studied using ab initio molecular orbital theory. The energetics and molecular parameters, calculated by the modified Gaussian-2 method (G2M), have been used to compute the reaction rate constants on the basis of the TST and RRKM theories. The reaction N2O + NO → N2 + NO2 (1) was found to proceed by direct oxygen abstraction and to have a barrier of 47 kcal/mol. The theoretical rate constant, k1 = 8.74 × 10-19 × T2.23 exp (-23,292/T) cm3 molecule-1 s-1, is in close agreement with earlier estimates. The reaction of N2O with OH at low temperatures and atmospheric pressure is slow and dominated by association, resulting in the HONNO intermediate. The calculated rate constant for 300 K ≤ T ≤ 500 K is lower by a few orders than the upper limits previously reported in the literature. At temperatures higher than 1000 K, the N2O + OH reaction is dominated by the N2 + O2H channel, while the HNO + NO channel is slower by 2-3 orders of magnitude. The calculated rate constants at the temperature range of 1000-5000 K for N2O + OH → N2 + O2H (2A) and N2O + OH → HNO + NO (2B) are fitted by the following expressions: $$k_{2A}=2.15\times 10^{-26}\times T^{4.72}\exp(-18,400/T),$$ $$k_{2B}=1.96\times 10^{-28}\times T^{4.33}\exp(-12,623/T),$$ in units of cm3 molecule -1s-1. Both N2O + NO and N2O + OH reactions are confirmed to enhance, albeit inefficiently, the N2O decomposition by reducing its activation energy. © 1996 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.8
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  • 3
    Electronic Resource
    Electronic Resource
    Absolute rate constant for the reaction of Phenyl radical with Acetylene (1994)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 26 (1994), S. 1095-1104 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The absolute rate constant for the reaction of phenyl radical with acetylene has been measured at 20 torr total pressure in the temperature range of 297 to 523 K using the cavity-ring-down technique. These new kinetic data could be quantitatively correlated with the data obtained earlier with a relative rate method under low-pressure (10-3-10-2 torr) and high-temperature (1000-1330 K) conditions. These kinetic data were analyzed in terms of the RRKM theory employing the thermochemical and molecular structure data computed with the BAC-MP4 technique.The calculated results reveal that the total rate constant for the C6H5 + C2H2 reaction (kt) is pressure-independent, whereas those for the formation of C6H5C2H (kb) and the C6H5C2H2 adduct (kc) are strongly pressure-dependent. A least-squares analysis of the calculated values for 300-2000 K at the atmospheric pressure of N2 or Ar can be given by \documentclass{article}\pagestyle{empty}\begin{document}$$ k_b = 9.5 \times {\rm 10}^{{\rm - 42}} T^{9.33} \exp \left({- 1,713/T} \right) $$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$ k_C = 1.8 \times {\rm 10}^{{\rm - 7}} T^{-1.63} \exp \left({- 2,711/T} \right) $$\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$$ k_t = 4.1 \times {\rm 10}^{{\rm - 18}} T^{1.77} \exp \left({- 1,152/T} \right) $$\end{document} all in units of cm3/s. The latter equation effectively represents the two sets of experimental data. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550261105
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  • 4
    Electronic Resource
    Electronic Resource
    The thermal reaction of HNCO at moderate temperatures (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 23 (1991), S. 1129-1149 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal reaction of HNCO has been studied in a static cell at temperatures between 873 and 1220 K and a constant pressure of 800 torr under highly diluted conditions. The reaction was measurable above 1000 K by FTIR spectrometry. The products detected include CO, CO2, HCN, NH3, and the unreacted HNCO. In this moderate temperature regime, the rates of product formation and HNCO decay cannot be accounted for by a previously established high-temperature mechanism, assuming HNCO → NH + CO (1) as the initiation process. Instead, a new bimolecular reaction, 2HNCO → CO2 + HNCNH (2), has been invoked to interpret the disappearance of HNCO as well as the formation of various products, most importantly CO2.The concentration profiles of all measured species can be quantitatively modeled, throughout the temperature range analyzed, by varying k2 using a modified mechanism. The kinetically modeled values of k2 can be effectively represented by \documentclass{article}\pagestyle{empty}\begin{document}$$ k_{\rm 2} = 10^{10.84 \pm 0.07} {\rm \,exp}(- 21,240 \pm 1,960/{\rm T}){\rm\, cm}^3 /{\rm mol\, s}{\rm .} $$\end{document}This result agrees closely with that computed with the conventional transition-state theory using the TST parameters predicted by the BAC-MP4 method: \documentclass{article}\pagestyle{empty}\begin{document}$$ k_2 ({\rm BAC} - {\rm MP}4) = 10^{11.13} {\rm \,exp(- 21,600/T) cm}^{\rm 3} /{\rm mol s}{\rm .} $$\end{document}The bimolecular reaction takes place via a stable 4-membered ring intermediate which is isoelectronic with diketene; viz.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550231206
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  • 5
    Electronic Resource
    Electronic Resource
    Theoretical interpretation of the kinetics and mechanisms of the HNO + HNO and HNO + 2NO reactions with a unified model (1992)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 24 (1992), S. 489-516 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Previously measured decay rates of HNO in the presence of NO have been kinetically modeled on the basis of thermochemical data calculated with the BAC-MP4 technique. The results of this modeling, aided by TST-RRKM calculations for the association of HNO and the isomerization, decomposition, and stabilization of the many dimers of HNO, reveal that the decay of HNO under NO-lean conditions occurs primarily by association forming cis- and trans-(HNO)2 at temperatures below 420 K. N2O, which is a relatively minor product, is believed to be formed by H2O elimination from cis-HON = NOH, a product of succesive isomerization reactions: trans-(HNO)2† → HN(OH)NO† → HN(O)NOH† → cis-HON NOH†. The calculated rate constants, which fit experimental data quantitatively, can be represented by k = 1016.2 × T-2.40e-590/T cm3/mol sec for the HNO recombination reaction and k = 10-2.44T3.98e-600/T cm3/mol sec for N2O formation in the temperature range 80-420 K, at a total pressure of 710 torr H2 or He.Under NO-rich conditions, HNO reacts predominantly by the exothermic termolecular reaction, HNO + 2NO → HN(NO)ONO → HN NO + NO2, with a rate contant of (6 ± 1) × 109 cm6/mol2 sec at room temperature, based on both HNO decay and NO2 production. All existing thermal kinetic data on HNO + HNO and HNO + 2NO processes can be satisfactorily rationalized with a unified model based on the thermochemical data obtained by BAC-MP4 calculations.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550240509
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  • 6
    Electronic Resource
    Electronic Resource
    A shock tube study of the CH2O + NO2 reaction at high temperaturesThe experiment was carried out at the U.S. Naval Research Laboratory with supports from the Office of Naval Research. (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 22 (1990), S. 455-482 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of CH2O with NO2 has been studied with a shock tube equipped with two stabilized ew CO lasers. The production of CO, NO, and H2O has been monitored with the CO lasers in the temperature range of 1140-1650 K using three different Ar-diluted CH2O-NO2 mixtures. Kinetic modeling and sensitivity analysis of the observed CO, NO, and H2O production profiles over the entire range of reaction conditions employed indicate that the bimolecular metathetical reaction, NO2 + CH2O → HONO + CHO (1) affects most strongly the yields of these products. Combination of the kinetically modeled values of k1 with those obtained recently from a low temperature pyrolytic study, ref. [8], leads to \documentclass{article}\pagestyle{empty}\begin{document}$$ k_1 = 8.02 \times 10^2 T^{2.77} e^{ - 6910/T} {\rm cm}^{\rm 3} /{\rm mol sec} $$\end{document} for the broad temperature range of 300-2000 K.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550220504
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  • 7
    Electronic Resource
    Electronic Resource
    Kinetics of CN reactions with N2O and CO2 (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 23 (1991), S. 151-160 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rate constants for the reaction of CN with N2O and CO2 have been measured by the laser dissociation/laser-induced fluorescence (two-laser pump-probe) technique at temperatures between 300 and 740 K. The rate of CN + N2O was measurable above 500 K, with a least-squares averaged rate constant, k = 10-11.8±0.4 exp(-3560 ± 181/T) cm3/s. The rate of CN + CO2, however, was not measurable even at the highest temperature reached in the present work, 743 K, with [CO2] ≤ 1.9 × 1018 molecules/cm3.In order to rationalize the observed kinetics, quantum mechanical calculations based on the BAC-MP4 method were performed. The results of these calculations reveal that the CN + N2O reaction takes place via a stable adduct NCNNO with a small barrier of 1.1 kcal/mol. The adduct, which is more stable than the reactants by 13 kcal/mol, decomposes into the NCN + NO products with an activation energy of 20.0 kcal/mol. This latter process is thus the rate-controlling step in the CN + N2O reaction. The CN + CO2 reaction, on the other hand, occurs with a large barrier of 27.4 kcal/mol, producing an unstable adduct NCOCO which fragments into NCO + CO with a small barrier of 4.5 kcal/mol. The large overall activation energy for this process explains the negligibly low reactivity of the CN radical toward CO2 below 1000 K.Least-squares analyses of the computed rate constants for these two CN reactions, which fit well with experimental data, give rise to \documentclass{article}\pagestyle{empty}\begin{document}$$ k_{{\rm N}_{\rm 2} {\rm O}} \, = \,6.4 \times 10^{- 21} {\rm T}^{{\rm 2}{\rm .6}} \exp (- 1860/{\rm T)cm}^{\rm 3} /{\rm s} $$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$ k_{{\rm C} {\rm O}_{\rm 2}} \, = \,6.1 \times 10^{- 18} {\rm T}^{{\rm 2}{\rm .2}} \exp (- 13530/{\rm T)cm}^{\rm 3} /{\rm s} $$\end{document} for the temperature range 300-3000 K.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550230206
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  • 8
    Electronic Resource
    Electronic Resource
    Thermal unimolecular decomposition of 1,3,5-trioxane: Comparison of theory and experiment (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 23 (1991), S. 947-956 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The unimolecular decomposition of 1,3,5-trioxane into three formaldehyde molecules has been studied thermally at eight temperatures between 523 and 603 K using mixtures highly diluted with Ar. Under these conditions, the only decomposition product detected by means of FTIR analysis was formaldehyde. At 588 K, the effect of total pressure was examined between 25 and 800 torr; a noticeable decline in the first-order rate constant was observed only at pressures below 500 torr. A least-squares analysis of the measured high-pressure, first-order rate constants leads to \documentclass{article}\pagestyle{empty}\begin{document}$$ k_1 = 10^{15.78 \pm 0.19} \exp [(- 25,620 \pm 254)/{\rm T]s}^{ - {\rm 1}} . $$\end{document} This result differs significantly from earlier data on the reaction, but it compares closely with the theoretical value: \documentclass{article}\pagestyle{empty}\begin{document}$$ k_1 ({\rm BAC} - {\rm MP}4) = 10^{15.67 \pm 0.01} \exp [(- 25,760 \pm 20)/{\rm T]s}^{ - {\rm 1}} . $$\end{document} computed with the transition-state theory using the molecular and TST parameters predicted by the BAC-MP4 method.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550231009
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  • 9
    Electronic Resource
    Electronic Resource
    Implications of the HCN → HNC process to high-temperature nitrogen-containing fuel chemistry (1992)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 24 (1992), S. 1103-1107 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have found in our recent kinetic study of the oxidation of HCN by NO2 in the temperature range 623-773 K that HNCO and CO2 are very important early products. The measured kinetic data cannot be accounted for by a “conventional” mechanism involving HCN reactions with NO2, O, and OH. However, the introduction of the isomerization reaction HCN → HNC, followed by the rapid oxidation of HNC by NO2, O, and OH, can quantitatively simulate all measured kinetic data. A similar study of the NO2 + HCN reaction in shock waves at temperatures between 1500 and 2400 K also required the inclusion of HNC reactions in order to quantitatively account for measured product distributions. The effects of the HNC molecule on the high temperature HCN chemistry are discussed in terms of the predicted rate constants for HNC reactions with O and OH employing the BAC-MP4 method. © John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550241208
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  • 10
    Electronic Resource
    Electronic Resource
    Thermal reaction of HNCO with NO2 at moderate temperatures (1993)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 25 (1993), S. 845-863 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal reaction of HNCO with NO2 has been studied in the temperature range of 623 to 773 K by FTIR spectrometry. Major products measured are CO2 and NO with a small amount of N2O. Kinetic modeling of the time resolved concentration profiles of the reactants and products, aided by the thermochemical data of various likely reactive intermediates computed by means of the BAC-MP4 method, allows us to conclude that the reaction is initiated exclusively by a new bimolecular process: with a rate constant, k1 = 2.5 × 1012e-13,100/T cm3/mols. The well-known bimolecular reaction is the only strong competitive process in this important reactive system throughout the temperature range studied. Kinetic modeling of NO formation and NO2 decay rates gave rise to values of k10 which were in close agreement with literature data. © 1993 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550251006
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