Theoretical study of the elimination kinetics of several 2-substituted ethyl N,N-dimethylcarbamates in the gas phase, [(CH3)2NCOOCH2CH2Z, Z=CH2Cl, C≡CH, C≡N]

Mirna M. Heredia R., Marcos Antonio Loroño Gonzalez, Tania Córdova, Gabriel Chuchani

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3 Scopus citations

Abstract

The theoretical studies of the gas-phase elimination of 2-substituted ethyl N,N-dimethylcarbamates (Z=CH2Cl, C≡CH, C≡N) were performed using ab initio MP2/6-31G and MP2/6-31G(d) levels of theory. The gas phase elimination reaction of these carbamates yields N,N-dimethylcarbamic acid and the corresponding substituted olefin in a rate-determining step. The intermediate N,N-dimethylcarbamic acid is unstable and rapidly decomposes through a four-membered cyclic transition state to dimethylamine and CO2 gas. The results of these calculations suggest a mechanism to be concerted, asynchronous, and a six-membered cyclic transition state structure. Plotting the relative theoretical rate coefficients against Taft's σ* values gave an approximate straight line (ρ*=0.4057, r=0.9894 at 360 °C). The correlation between experimental log krel vs. theoretical log krel. for these 2-substituted ethyl N,N-dimethylcarbamates gave an approximate straight line (r=0.9715 at 360 °C), suggesting the same type of mechanism.

Original languageEnglish
Pages (from-to)131-137
Number of pages7
JournalJournal of Molecular Structure: THEOCHEM
Volume770
Issue number1-3
DOIs
StatePublished - 29 Sep 2006
Externally publishedYes

Bibliographical note

Copyright:
Copyright 2006 Elsevier B.V., All rights reserved.

Keywords

  • 2-Substituted ethyl N,N-dimethylcarbamates
  • Gas-phase elimination
  • Mechanism
  • MP2 calculations
  • Substituent effects

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