THE REACTIONS OF SELECTED ACETATES WITH THE OH RADICAL IN THE PRESENCE OF NO - NOVEL REARRANGEMENT OF ALKOXY RADICALS OF STRUCTURE RC(O)OCH(O)R

Products of the gas-phase reactions of the OH radical with ethyl aceta te, isopropyl acetate, tert-butyl acetate in the presence of NO were i nvestigated using in situ Fourier transform infrared spectroscopy and gas chromatography. The products identified and their molar formation yields (corrected for secondary reactions with the OH radical) were ac etic acid (0.96 +/- 0.08) from ethyl acetate; acetic acid (0.09 +/- 0. 03), acetic anhydride (0.76 +/- 0.07), and acetone (0.24 +/- 0.02) fro m isopropyl acetate; and acetic anhydride (0.49 +/- 0.05) and acetone (0.20 +/- 0.02) from tert-butyl acetate. Consideration of the potentia l reaction pathways of the intermediate alkoxy radicals leads to the c onclusion that alkoxy radicals of structure RC(O)OCH((O) over dot)R ca n undergo a rapid rearrangement and decomposition (alpha-ester rearran gement) to RC(O)OH plus R(C) over dotO, presumably via a five-membered ring transition state. However, our product studies provided no evide nce for the analogous beta-ester rearrangement proceeding via a six-me mbered transition state, although the possibility that this reaction c ould occur is not ruled out.