The unimolecular thermal decomposition of oxetane and its methyl derivatives: An Ab initio and RRKM calculations

Abstract

Quantum mechanical and Rice-Ramsperger-Kassel-Marcus (RRKM) calculations are carried out to study the thermal unimolecular decomposition of oxetane (1), 2 methyloxetane (2), and 2,2 dimeth yloxetane (3) at the MPW1PW91/6 311 + G** level of theory. The results of the calculations reveal that decomposition reaction of compounds 1-3 yields formaldehyde and the corresponding substituted olefin. The predicted high pressure limit rate constants for the decomposition compounds 1-3 are represented as 6.61 × 10 13 exp(-32472/T), 9.33 × 10 13 exp(-29873/T), and 4.79 × 10 13 exp(-27055/T) s -1 , respectively. The fall off pressures for the decomposition of compounds 1-3 are found to be 9.42 × 10 -2 , 3.67 × 10 -3 , and 7.26 × 10 -4 mm Hg, respectively. As the fall off pressure of the decomposition process of compounds 1-3 are in the following order: P 1/2 (1) > P 1/2 (2) > P 1/2 (3); therefore the decomposition rates are as follow: rate(1) < rate(2) < rate(3).

Chemical kinetics of cyclic ethers in combustion

“…Experiments by [594,610,[613][614][615][616] and theoretical results by, e.g., [617][618][619] show that unimolecular reactions may contribute substantially to CE decomposition. For example, in oxirane pyrolysis and combustion, acetaldehyde has been detected in high amounts.…”

Density functional theoretical studies on the ring-opening polymerization mechanism of oxetane cation series compounds

“…There has been some theoretical research carried out on the electronic structure of oxetane. Most work has been focused on calculating the structural properties of monomers and complexes, [15][16][17][18] or the reaction mechanisms of pyrolysis [19][20][21] and photolysis [22][23][24] of oxetane. Ferreira et al 15 predicted the structural stability of a complex of the oxetane monomer with hydrogen halide and discussed the special nature of the weak interaction using density functional theory calculations at the B3LYP/6-311++G(d,p) level.…”

“…Earlier, Chen et al 19 explored the pyrolysis reaction mechanism of oxetane using a semi-empirical molecular orbital method, and indicated that the biradical reaction was the most interesting process in the variety of primitive reaction pathways. Recently, Tahan 20 and Shiroudi 21 determined that formaldehyde and an olen were the main products of oxetane single molecule pyrolysis, and gave a high-pressure limit of the reaction rate constants according to computations using B3LYP/6-311+G**, B3PW91/6-311+G** and MPW1PW91/6-311+G**. Studies investigating the photolysis reaction mechanism in oxetane polymerization have gradually increased.…”

Pinpointing Double Bonds in Lipids by Paternò‐Büchi Reactions and Mass Spectrometry

“…[15] Depending on the relative positions of the carbonyl and the C = C bond, two position isomers of the oxtanes can be formed as shown in Scheme 1. If energy (such as heating) is applied to the P-B reaction products, retro P-B reactions can happen, [16] through two possible pathways. One route leads back to the original reactants.…”

“…The two acyl chain lengths are determined to be C 16 and C 18 by considering the general formula (C n H 2nÀ1 CO 2 À ) of the deprotonated FA ions (m/z 281.2 and 253.2). Putting the information together, it is straightforward to conclude that one acyl chain is C 16 with a double bond between C9 and C10, and the other one is a C 18 chain containing a double bond between C9 and C10. The above procedure also forms the basis for structural characterization of unsaturated lipids in a complex lipid mixture shown later in this study.…”