Catalysis by hydrogen halides in the gas phase. X. Tertiary butyl methyl ether and hydrogen chloride

Abstract

The decomposition of t-butyl methyl ether catalysed by hydrogen chloride takes place at 337-428�. It is first order in each reactant and the rate is not affected by increase in surface area or inhibitor. The rate equation is: K2 = 1012.46exp(-32100/RT) (sec-l ml mole-l) The reaction is believed to be molecular and its properties are in accord with those of other such catalysed decompositions.

Unveiling the structure‐reactivity relationship involved in the reaction mechanism of the HCl‐catalyzed alkyl t‐butyl ethers thermal decomposition. A computational study

“…The highest evolution percentage was found for the Cl1 H2 bond ($90%) for both mechanisms. This means that the halide substitution will have a significant influence on the reaction mechanism, which agrees with a consistent ratio of 30:1 when hydrogen bromide is used instead of hydrogen chloride [6]. Looking at the ether, the bond evolving the most is O3 C4 in reaction route I and O3 C7 in reaction route II.…”

“…In the first stage, the HCl catalyzed gas-phase decomposition of t-butyl methyl ether (A), t-butyl ethyl ether (B), and t-butyl isopropyl ether (C) [2,4,6] was evaluated computationally following Scheme 1. Thermodynamic parameters estimated are reported in Table 1.…”

“…Experimental activation energies found for these systems are about 130 kJ/mol [2, 4, 6], while computational results show an activation free energy around 136 kJ/mol using ωB97XD and 160 kJ/mol using the CCSD(T) correction. This suggests that, although there is a reasonable agreement between experimental and theoretical calculations, a subtle overestimation is obtained in the estimation of the activation free energy.…”

“…In the literature, the experimental results of the gas‐phase decomposition of t‐ butyl methyl ether [6], t‐ butyl ethyl ether [2], and t‐ butyl isopropyl ether [4] catalyzed by hydrogen chloride are reported. To the best of our knowledge, mechanistic studies carried out at the atomistic level have not been performed to elucidate the gas‐phase decomposition mechanism of ethers using hydrogen chloride as a catalyst.…”

“…It has been reported that hydrogen halides can be employed to catalyze gas‐phase decomposition [1, 2] of several oxygenated organic compounds, such as alcohols, ethers, acids, and esters [3]. Reported reactions include the decomposition of butan‐2‐ol [1], acetaldehyde dimethyl acetal, 1,l‐dimethoxyethane [3], t‐ butyl isopropyl ether [4], 2,2‐dimethoxypropane [5], t‐ butyl methyl ether [6], t‐ butyl ethyl ether [2], and t‐ butylamine [7]. The uncatalyzed reaction of the latter compounds produces dehydrogenation, which is believed to occur through a radical chain mechanism [2, 3, 7].…”