Computational study of the thermal decomposition of some oxypropenes
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ORIGINAL PAPER
Computational study of the thermal decomposition of some oxypropenes Pablo Ruiz 1,2
&
Jairo Quijano 1
Received: 14 May 2020 / Accepted: 31 August 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract This work aims at describing the computational study of thermal decomposition reaction of three oxypropenes: 2-(1methylethoxy)propene, 2-ethoxypropene, and 2-butoxypropene. It was carried out in order to delve into the reaction mechanism proposed in experimental studies. Computational optimization calculations and frequencies of the structures were performed with the M06-2X/6-311+G(d,p) method at different temperatures ranging from 600 to 640 K. The rate constants were calculated with the classical transition state theory, and the values obtained are of the same order as the reported experimental values. The results derived from the population partitioning technique indicate that transition states are symmetrical and the mechanism is concerted and highly synchronous. Keywords 2-Butoxypropene . 2-Ethoxypropene . 2-(1-Methylethoxy)propene . Thermal decomposition . Unimolecular reaction
Introduction There are numerous experimental [1–8] and computational studies [9–14] available on thermal decomposition reaction of vinyl ethers. Previous studies on these compounds indicate that they decompose through a retro-ene-type unimolecular reaction mechanism, through a cyclical transition state. There is also evidence of a minor, secondary, and radical mechanism, negligible at low temperatures. Yet, studies on oxypropene compounds are few. They can be seen as vinyl ether–type molecules substituted with a methyl group on the vinyl carbon. Experimental studies on molecules 2-(1-methylethoxy)propene [15], 2-ethoxypropene [16], and 2-butoxypropene [17] report that the decomposition reaction involves first-order kinetics, a Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00894-020-04530-1) contains supplementary material, which is available to authorized users. * Pablo Ruiz [email protected] 1
Laboratorio de Fisicoquímica Orgánica, Facultad de Ciencias, Universidad Nacional de Colombia, Medellin Headquarters, Medellín 050034, Colombia
2
Facultad de Ciencias Exactas y Aplicadas, Instituto Tecnológico Metropolitano, Medellín, Colombia
concerted unimolecular mechanism, and it occurs through a sixmembered cyclical transition state of a certain ionic character. Researchers also report a negligible pressure effect on the rate constant. For decomposition of 2-ethoxypropene, the presence of a radical route is also reported. From the results of these studies, researchers concluded that the rate constant (k) of the studied oxypropenes increases in relation to the value of the constant for the decomposition reaction of the equivalent molecules in the vinyl ether. In this study, the thermal decomposition reaction of some oxypropenes has been modeled at five different temperatures to evaluate the effect of the methyl group as a substituent on vinyl carbon,
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