Infrared laser-powered homogeneous pyrolysis, coupled with Fourier-transform infrared measurement of product distributions, has demonstrated that four different unimolecular mechanisms are significant in the initiation of gas-phase thermal decomposition of CH3COOH (1), CF3COOH (2), CH2ClCOOH (3), CHCl2COOH (4), CCl3COOH (5), CH2BrCOOH (6), and CH2ICOOH (7): decarboxylation and dehydration for (1); H-X elimination for (2)-(6); and C-X bond homolysis for (6) and (7). These conclusions are supported by the semiempirical calculation of activation energies for the possible pathways.

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