Addition reaction of adamantylideneadamantane with Br-2 and 2Br(2)

a computational study

Shahidul M. Islam, Raymond A. Poirier*

*Corresponding author for this work

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Ab initio calculations were carried out for the reaction of adamantylideneadamantane (Ad=Ad) with Br-2 and 2Br(2). Geometries of the reactants, transition states, intermediates, and products were optimized at HF and B3LYP levels of theory using the 6-31G(d) basis set. Energies were also obtained using single point calculations at the MP2/6-31G(d)//HF/6-31G(d), MP2/6-31G(d)//B3LYP/6-31G(d), and B3LYP/6-31+G(d)//3LYP/6-31G(d) levels of theory. Intrinsic reaction coordinate (IRC) calculations were performed to characterize the transition states on the potential energy surface. Only one pathway was found for the reaction of Ad=Ad with one Br2 producing a bromonium/bromide ion pair. Three mechanisms for the reaction of Ad=Ad with 2Br2 were found, leading to three different structural forms of the bromonium/Br-3(-) ion pair. Activation energies, free energies, and enthalpies of activation along with the relative stability of products for each reaction pathway were calculated. The reaction of Ad=Ad with 2Br(2) was strongly favored over the reaction with only one Br-2. According to B3LYP/6-31G(d) and single point calculations at MP2, the most stable bromonium/Br-3(-) ion pair would form spontaneously. The most stable of the three bromonium/Br3- ion pairs has a structure very similar to the observed X-ray structure. Free energies of activation and relative stabilities of reactants and products in CCl4 and CH2ClCH2Cl were also calculated with PCM using the united atom (UAO) cavity model and, in general, results similar to the gas phase were obtained. An optimized structure for the trans-1,2-dibromo product was also found at all levels of theory both in gas phase and in solution, but no, transition state leading to the trans-1,2-dibromo product was obtained.

Original languageEnglish
Pages (from-to)152-159
Number of pages8
JournalJournal of Physical Chemistry A
Volume112
Issue number1
DOIs
Publication statusPublished - 10 Jan 2008
Externally publishedYes

Keywords

  • ION-CYCLOTRON RESONANCE
  • CYCLIC HALONIUM IONS
  • ELECTROPHILIC BROMINATION
  • BROMONIUM ION
  • GAS-PHASE
  • REVERSIBLE FORMATION
  • RELATIVE STABILITIES
  • ACYL CATIONS
  • OLEFINS
  • SYSTEM

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