The reaction mechanism of the gas-phase thermal decomposition kinetics of neopentyl halides: A DFT study

Authors

  • José R. Mora,

    1. Centro de Química, Instituto Venezolano de Investigaciones Científicas (I.V.I.C.), Apartado 21827, Caracas, Venezuela
    Search for more papers by this author
  • Edgar Márquez,

    1. Departamento de Química, Escuela de Ciencias, Universidad de Oriente, Cumaná, Venezuela
    Search for more papers by this author
  • Jesus Lezama,

    1. Centro de Química, Instituto Venezolano de Investigaciones Científicas (I.V.I.C.), Apartado 21827, Caracas, Venezuela
    Search for more papers by this author
  • Tania Córdova,

    1. Escuela de Química, Facultad de Ciencias, Universidad Central de Venezuela, Apartado 1020-A, Caracas, Venezuela
    Current affiliation:
    1. Tania Códova is currently at Department of Medicinal Chemistry, College of Pharmacy, University of Florida, P.O. Box 100485, Gainesville, FL 32610, USA
    Search for more papers by this author
  • Gabriel Chuchani

    Corresponding author
    1. Centro de Química, Instituto Venezolano de Investigaciones Científicas (I.V.I.C.), Apartado 21827, Caracas, Venezuela
    • Centro de Química, Instituto Venezolano de Investigaciones Científicas (I.V.I.C.), Apartado 21827, Caracas, Venezuela
    Search for more papers by this author

Abstract

The kinetics and mechanisms of the gas-phase elimination reactions of neopentyl chloride and neopentyl bromide have been studied by means of electronic structure calculations using density functional methods: B3LYP/6-31G(d,p), B3LYP/ 6-31++G(d,p), MPW1PW91/6-31G(d,p), MPW1PW91/6-31++G(d,p), PBEPBE/6-31G(d,p), PBEPBE /6-31++G(d,p). The reaction channels that account in products formation have a common first step involving a Wagner-Meerwein rearrangement. The migration of the halide from the terminal carbon to the more substituted carbon is followed by beta-elimination of HCl or HBr to give two olefins: the Sayzeff and Hoffmann products. Theoretical calculations demonstrated that these eliminations proceed through concerted asynchronous process. The transition state (TS) located for the rate-determining step shows the halide detached and bridging between the terminal carbon and the quaternary carbon, while the methyl group is also migrating in a concerted fashion. The TS is described as an intimate ion-pair with a large negative charge at the halide atom. The concerted migration of methyl group provides stabilization of the TS by delocalizing the electron density between the terminal carbon and the quaternary carbon. The B3LYP/6-31++G(d,p) allows to obtain reasonable energies and enthalpies of activation. The nature of these reactions is examined in terms of geometrical parameters, electron distribution, and bond order analysis. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011

Ancillary