Determination of the kinetic parameters of the isomerization reaction of ethyl isocyanide using HeI photoelectron spectroscopy

Abstract

The use of HeI photoelectron spectroscopy (PES) for the kinetic study of chemical reactions was introduced previously by us. As another example of the determination of the kinetic parameters of a chemical reaction using the PES method, the isomerization reaction of ethyl isocyanide CH3CH2NC → CH3CH2CN is investigated. It is found to be first order and the kinetic equations at 193.6, 200.0 and 210.3°C can be expressed as ln R466.6 K = − (7.600 ± 0.026) × 10−5t − 0.4350; ln R473.0 K = − (1.329 ± 0.032) × 10−4 − 0.4375 and ln R483.3 K = − (3.170 ± 0.052) × 10−4 − 0.4354, respectively. The rate constants of the reactions at 193.6, 200.0 reactions at 193.6, 200.0 and 210.3°C are respectively (7.600 ± 0.026) × 10−5, (1.329 ± 0.032) × 10−4 and (3.170 ± 0.052) × 10−4 s−1. The calculated activation energy (Ea) of this isomerization reaction is 38.36 ± 0.32 kcal mol−1. These results are also in excellent agreement with the results obtained by a traditional method. This means that PES is a valuable method for determining the kinetic parameters of chemical reactions. The value of the intercept in the kinetic equations is related to the logarithm of the ratio of the photoionization cross-section of the bands used. This also means that the relative photoionization cross-sections of the bands used for the sample studied are obtained in the kinetic study of a chemical reaction using the PES method.