DFT Study of substituent effects of 2-substituted alkyl ethyl methylcarbonates in homogeneous, unimolecular gas phase elimination kinetics

✍ Scribed by Rafael Añez; Armando Herize; Aníbal Sierraalta; Tania Cordova; Gabriel Chuchani

• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: English
• Weight: 178 KB
• Volume: 38
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.20159

✦ Synopsis

Abstract

Theoretical studies on the gas phase elimination of 2‐substituted alkyl ethyl methylcarbonates were performed at the B3LYP/6‐31G* and B3LYP/6‐31+G** level of theory. The results of these calculations provide additional evidence that the mechanism of carbonates with a C~β~H bond proceeds through a concerted nonsynchronous six‐membered cyclic transition state to produce methylcarbonic acid and the corresponding olefin. The unstable intermediate, methylcarbonic acid, rapidly decomposes through a four‐membered cyclic transition state to methanol and carbon dioxide. The correlation of the logarithm of theoretical rate coefficients against Hancock's steric parameters E gave an approximate straight line (δ = 0.30, r = 0.996 at 400°C). An additional fact is that when experimental log k~re.l~ is plotted against the theoretical log k~re.l.~ for 2‐alkyl ethyl methylcarbonates an approximate straight line (r = 0.997 at 400°C) is obtained. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 184–193, 2006