Molecular Structures of Acetyl Chloride and Acetyl Bromide as Determined by Gas Electron Diffraction

Abstract

Abstract The molecular structures of acetyl chloride and acetyl bromide have been investigated by the sector-micro-photometer method of gas-phase electron diffraction. The thermal average distances, rg, and the valence angles, \varphia, have been determined, with estimated limits of error, to be as follows: for acetyl chloride, rg(C=O)=1.187±0.003 Å, rg(C–Cl)=1.798±0.003Å, rg(C–C)=1.508±0.005 Å, \varphia(OCCl)=120.3°±0.6°, \varphia(CCCl)=112.2°±0.09°, and \varphia(CCO)=127.5°±0.9°; and for acetyl bromide, rg(C=O)=1.184±0.004 Å, rg(C–Br)=1.975±0.004 Å, rg(C–C)=1.518±0.008Å, \varphia(OCBr)=120.8°± 0.9°, \varphia(CCBr)=109.5°±1.2°, and \varphia(CCO)=129.7°±1.1°. The C=O distances in these molecules are shorter than those in acetaldehyde and acetone by about 0.02 Å. This may be attributed to the effect of a highly electronegative halogen atom adjacent to the carbonyl group.