Intramolecular isotopic effect in the pyrolysis of ethyl‐2d1 chloride

The thermal decomposition of deuterated ethyl chloride CH2DCH2Cl was studied in a static system in the pressure range of 0.1–26 torr, and the Arrhenius expression for the overall decomposition at the high-pressure limit and in the temperature range of 670–1100 K was found to be The intramolecular isotopic effects were first examined in the pressure range of 0.1–26 torr at 837 K, and the branching ratio kH/kD was found to decrease with increasing pressure. The RRKM-theory calculations describe the experimental data well. The intramolecular isotopic effect was also examined in the temperature range of 728–926 K, and the branching ratio at the high pressure limit was given by the expression when kH and kD are the rate constants for the HCl and DCl channels of elimination. The Arrhenius A factors obtained at the high-pressure limit together with the temperature-dependent expression of the branching ratio provided additional experimental data for an assignment (fine-tuned) of the vibrational frequencies of both activated complexes involved in the thermal decomposition of CH2DCH2Cl. The evaluated vibrational frequencies were then used in the RRKM calculations describing the pressure dependence of the intramolecular isotopic effect. The RRKM calculations and the experimental data were in good agreement, supporting the choice of vibrational frequencies for both the activated complexes as well as the transition-state model.

[1]  H. Heydtmann,et al.  The Thermal Unimolecular Decompositions of CH3CD2Cl, CD3CD2Cl, and CH3CHCl2 , 1978 .

[2]  S. Benson,et al.  Intramolecular isotope effect in laser multiphoton dissociation of CH2DCH2Cl , 1977 .

[3]  H. Heydtmann,et al.  Application of Forst's method to the calculation of thermal unimolecular reaction rates and isotope effects in the falloff region , 1977 .

[4]  H. Heydtmann,et al.  The thermal unimolecular decompositions of C2H5Cl, i‐C3H7Cl, and t‐C4H9Cl , 1975 .

[5]  I. Tvaroška,et al.  On thermal dehydrochlorination of model compounds for poly(vinyl chloride)—II , 1974 .

[6]  F. Miller,et al.  The vibrational spectra of several ethyl chlorides: CH3CH2Cl, CH3CD2Cl, CD3CH2Cl, and CD3CD2Cl , 1969 .

[7]  D. Setser,et al.  Kinetic Isotope Effects in the Unimolecular Reactions of Chemically Activated Chloroethane‐d0 and ‐d5 and 1,2‐Dichloroethane‐d0 and ‐d4 Molecules , 1968 .

[8]  S. Benson,et al.  A Method for Estimating the Arrhenius A Factors for Four- and Six-Center Unimolecular Reactions , 1967 .

[9]  A. Marsh,et al.  Unimolecular gas-phase pyrolysis of ethyl chloride , 1967 .

[10]  D. Setser,et al.  RRKM Calculated Unimolecular Reaction Rates for Chemically and Thermally Activated C2H5Cl, 1,1‐C2H4Cl2, and 1,2‐C2H4Cl2 , 1966 .

[11]  S. Benson,et al.  A Simple, Self-Consistent Electrostatic Model for Quantitative Prediction of the Activation Energies of Four-Center Reactions1 , 1965 .

[12]  S. Benson,et al.  Structural Aspects of the Kinetics of Four‐Center Reactions in the Vapor Phase , 1963 .

[13]  A. Blades,et al.  THE HYDROGEN ISOTOPE EFFECTS IN THE PYROLYSIS OF ETHYL-1,1,2,2-d4 BROMIDE AND OF ETHYL-d5 BROMIDE , 1962 .

[14]  A. Blades,et al.  THE HYDROGEN ISOTOPE EFFECT IN THE PYROLYSIS OF ETHYL-1,1,2,2-d4 CHLORIDE , 1960 .

[15]  A. Blades.  THE KINETICS OF THE THERMAL DECOMPOSITION OF ETHYL BROMIDE AND ETHYL BROMIDE-d5 , 1958 .

[16]  J. Nielsen,et al.  Vibrational Spectra and Calculated Thermodynamic Properties of Ethyl Chloride and 1,1‐Dichloroethane , 1954 .