Density functional theory investigation of the reactions of CH2Br–I, CH2I–Br, CH2Cl–I, and CH2I–Cl isopolyhalomethanes with ethylene

Abstract

We report density functional theory calculations that examine the chemical reactivity of the iso-CH₂X–I and iso-CH₂I–X (where X = Br or Cl) species with ethylene and their isomerization reactions. The carbenoid properties and isomerization reactions of these CH₂X–Y species were compared to those found previously for the CH₂X–X species (where X = I, Br or Cl). The chemical reactivity of the iso-CH₂X–I and iso-CH₂I–X species varies with the electronegativity of the X atom and the position of the X atom in the carbon–halogen–halogen moiety. In addition, the C–X–I or C–I–X bond angles and I–X bond lengths (which vary more than in the iso-CH₂X–X species) also appear to influence the chemical reactivity of the iso-CH₂X–I and iso-CH₂I–X species. We briefly discuss the properties of these cyclopropanation and isomerization reactions and likely consequences for using different isopolyhalomethanes and other species as methylene transfer agents.