ELIMINATION KINETICS OF DL-MANDELIC ACID IN THE GAS-PHASE

DL-Mandelic acid was pyrolyzed in a static reaction vessel over the te mperature range 300.1-340.0 degrees C and pressure range of the substr ate 15.2-52.1 Torr. The reaction, in a seasoned vessel and in the pres ence of the free radical inhibitor cyclohexene, is homogeneous, unimol ecular and obeys a first-order rate law, The reaction yielded benzalde hyde, CO, H2O and small amounts of benzyl alcohol and CO2. The rate co efficients followed the Arrhenius equation: log k(1) (s(-1)) = (12.54 +/- 0.12)-(171.3 +/- 1.4)kJ mol(-1) (2.303RT)(-1). The present result; may imply a unimolecular elimination involving a semi-polar five-memb ered cyclic transition state mechanism, Steric factor appears not to b e important in rate enhancement. (C) 1997 by John Wiley & Sons, Ltd.