Kinetics and mechanism of thermal gas-phase elimination of β-substituted carboxylic acids

3-Phenoxypropanoic acid (), 3-(phenylthio)propanoic acid (), and 4-phenylbutanoic acid () were pyrolysed between 520 and 682 K. Analysis of the pyrolysates showed the elimination products to be acrylic acid and the corresponding arene. Pyrolysis of ethyl 3-phenoxypropanoate () and its methyl analogue (), ethyl 3-(phenylthio)propanoate () and its methyl counterpart (), and 3-phenoxypropane nitrile () were also investigated between 617 and 737 K. The thermal gas-phase elimination kinetics and product analysis are compatible with a thermal retro-Michael reaction pathway involving a four-membered cyclic transition state.