DFT Calculations on Retro-Ene Reactions Part I: Allyl n-Butyl Sulfide Pyrolysis in the Gas Phase

Abstract

The mechanism and kinetic aspects of the retro-ene reaction of allyl n-butyl sulfide and its deuterated derivative were studied using four different types of density functional theory (DFT) methods with eight different levels of the basis sets. Vibrational frequency analysis confirmed that the stationary points include the transition state (TS) structure with only one imaginary frequency. Mechanistic studies on the retro-ene process rejected the step-wise mechanism and confirmed that the reaction proceeds through a six-centered cyclic transition state. Theoretical calculations show that propene elimination from the reactant can occur through an asynchronous concerted mechanism. A primary kinetic isotope effect of 2.21 for the reaction can be determined. Theoretical kinetics and activation energies especially at the B3LYP/6-31G* levels are in good agreement with the experimental values.

First-Principles Calculations on the Kinetics and Mechanism of the Retro-Ene Reaction of Diallyl Amine in the Gas Phase

“…These values at the B3LYP=6-311 þ þ G(d,p), B3LYP=Aug-cc-pvtz and MP2=6-311 þ þ G(d,p) levels of the theory are 189.58, 190.03 and 181.22 kJ mol À 1 , respectively. From the comparative viewpoint, it can be concluded that the B3LYP=6-31 þ G(d,p) approach is the best method, which is in accordance to our previous studies [3,5]. The negative value for the activation entropy shows that the retro-ene reaction proceeds through a concerted cyclic TS.…”

Kinetics and mechanism of diallyl sulfoxide pyrolysis; a combined theoretical and experimental study in the gas phase

“…The most popular concerted mechanism for the retro-ene reaction includes a six-membered transition structure (TS). [1][2][3][4][5][6][7][8] Two convenient methods for direct conversion of sulfoxides to olens are base-catalyzed b-elimination and simple pyrolysis. A yield of 90% of propene was reported by heating of diisopropyl sulfoxide and potassium-tbutoxide in dimethyl sulfoxide as solvent for 17 hours at 358 K. 9 In comparison, thermal elimination requires a higher temperature but is potentially a cleaner reaction.…”