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 CH 3 group is the stabilization of the transition state formed in the reaction and therefore a small increase in the rate of thermal decomposition. C

Understanding the thermal dehydrochlorination reaction of 1-chlorohexane. Revealing the driving bonding pattern at the planar catalytic reaction center

“…1 Scheme 1. Our main goal is the characterization of the electronic patterns governing cyclic transition states, [19][20][21][22][23][24][25][26][27][28] , therefore we will focus on the nature of bonding of the thermal decomposition of 1chlorohexane reaction mechanism as a benchmark of this type of reactivity in gas phase. The nature of bonding at the catalytic reaction center for the electronic rearrangement (i.e., Cl-C α -C β -H β ) remains unknown.…”

“…3,[8][9][10][11][12][13][14][15][16][17][18] The intimate nature of the electronic rearrangement driving this type of transformations remains certainly unknown. Our main goal is the characterization of the electronic patterns governing cyclic transition states, [19][20][21][22][23][24][25][26][27][28] therefore we will focus on the nature of bonding of the thermal decomposition of 1-chlorohexane reaction mechanism as a benchmark of this type of reactivity in gas phase. 2,4,9,10 Our discussion will be based on results from local measures of the same spin pair density distribution as given through the topological analysis of the electron localization function (ELF), 29,30 i.e., a relative but proper measure of Pauli repulsion at the local level.…”