The elimination kinetics of 2-chloropropionic acid have been studied over the temperature range of 320-370.2"C and pressure range of 79-218.5 torr. The reaction in seasoned vessel and in the presence of the free radical suppressor cyclohexene, is homogeneous, unimolecular, and obeys a first-order rate law. The dehydrochlorination products are acetaldehyde and carbon monoxide. The rate coefficient is expressed by the following Arrhenius equation: log k , ( s -' ) = (12.53 2 0.43) -(186.9 t 5.l)kJ mol-' (2.303RT)-'. The hydrogen atom of the carboxylic COOH appears to assist readily the leaving chloride ion in the transition state, suggesting an intimate ion pair mechanism operating in this reaction.

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The rates of elimination of primary, secondary and tertiary a-hydroxycarboxylic acids were determined in a seasoned, static reaction vessel over the temperature range 280-390 OC and the pressure range 30-201 Tom. The reactions, in the presence of a free radical inhibitor, are homogeneous, unimolecular and follow a first-order rate law. The rate coefficients are given b the following equations: for Flycolic acid, log k1 (s-') = (14.03 It 0.24) -(209.3 4 1.5) kJmol-'(2.30387')-'; for lactic acid, lo k~ (s-) = (12.24 It 0.11) -(182.8 It 1.3) kJmol-' (2*30317')-'; and for ease with which the hydroxy group is removed from primary to tertiary a-hydroxycarboxylk acids are reflected in rate enhancement. The mechanism of these eliminations appears to proceed through a semi-polar Bve-membered cyclic transition state.2-hydroxyisobutyric acid, log k~ (s-k ) = (12-91 -C 0-13) -(174.7 f 1.5) W mol-' (2*303R7')-'. The basicity and the

The decomposition of three alkoxyacetic acids, methoxy, ethoxy, and isopropoxy acetic acids, has been studied by using ab initio calculations at the MP2/6-31G** level. Molecular mechanisms A and B have been characterized, corresponding to stepwise processes with formation of the corresponding alcohol and an α-lactone intermediate, achieved by the nucleophilic attack of either carbonylic or hydroxylic oxygen atoms followed by a ring opening process to yield formaldehyde and carbon monoxide. For ethoxyacetic and isopropoxyacetic acids, three additional reactive channels were thought to be possible on potential energy surface; mechanisms C and D are elimination processes to give the corresponding alkene and glycolic acid. The reaction pathways along mechanisms C and D take place by the transfer of a β-hydrogen atom, with respect to the ether group, from the terminal methyl group to the hydroxylic or the alkoxylic oxygen atoms, respectively. The glycolic acid formed in the first step is then submitted to decomposition by water elimination and α-lactone intermediate formation. A final ring opening process yields formaldehyde and carbon monoxide. Molecular mechanism E is associated with a fragmentation process along a concerted one-step with concomitant formation of the corresponding alquene, formaldehyde, water, and carbon monoxide. The decomposition process is energetically favorable along the mechanism A, and the calculated rate coefficients agree with experimental data.

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