Experimental and computational study of the thermal decomposition of 3-methyl-3-buten-1-ol in m-xylene solution

Abstract

An experimental study of the thermal decomposition of a β-hydroxy alkene, 3-methyl-3-buten-1-ol, in m-xylene solution, has been carried out at five different temperatures in the range of 513.15-563.15 K. The temperature dependence of the rate constants for the decomposition of this compound in the corresponding Arrhenius equation is given by ln k (s-1) = (25.65 ± 1.52) - (17,944 ± 814) (kJ·mol-1) ·T-1. A computational study has been carried out at the M05-2X/6-31+G(d,p) level of theory to calculate the rate constants and the activation parameters by the classical transition state theory. There is a good agreement between the experimental and calculated rate constants and activation Gibbs energies. The bonding characteristics of reactant, transition state, and products have been investigated by the natural bond orbital analysis, which provides the natural atomic charges and the Wiberg bond indices. Based on the results obtained, the mechanism proposed is a one-step process proceeding through a six-membered cyclic transition state, being a concerted and slightly asynchronous process. The results have been compared with those obtained previously by us (Struct Chem 2013, 24, 1811-1816) for the thermal decomposition of 3-buten-1-ol, in m-xylene solution. We can conclude that in the compound studied in this work, 3-methyl-3-buten-1-ol, the effect of substitution at position 3 by a weakly activating CH3 group is the stabilization of the transition state formed in the reaction and therefore a small increase in the rate of thermal decomposition. © 2014 Wiley Periodicals, Inc.