EFFECT OF THE DISTRIBUTION OF PYRIDINE 1-OXIDE ON ITS CATALYZED 2-PHASE REACTION OF BENZOYL CHLORIDE AND CARBOXYLATE ION

Benzoyl chloride (PhCOCl) exhibits a peculiar inhibitve effect on its reaction with some sodium carboxylates (RCOONa) catalyzed by pyridine 1-oxide (PNO) in a CH2Cl2/H2O medium. However, the reaction follows we ll the rate law-d[PhCOCl](org)/dt = k(obs)[PhCOCl](org) = (k(h) + k(c) [PNO](i,aq))[PhCOCl](org). Where k(h) is the uncatalyzed rate coeffic ient, k(c), is the catalyzed rate coefficient, and [PNO](i,aq) is the initial concentration of PNO in aqueous phase. When the concentration of RCOONa is the sufficiently high, k(obs) can be expressed as k(obs) = k(h) + k(PNO)[PNO](i,aq)/(1 + k(PNO)). Where k(PNO) is the intrinsic rate coefficient of the reaction between PhCOCl and PNO in CH2Cl2 and k(PNO) is the distribution constant of PNO between H2O/CH2Cl2 phases and is defined as k(PNO)(?)[PNO](aq)/[PNO](org). In order to account f or this peculiar phenomenon, the effects of organic compounds, includi ng CCl4, alcohol, ester, and carboxylic acid, were investigated. The p resence of organic additive affects the distribution of PNO between H2 O and CH2Cl2 phases, the reaction rate, and the yield of product. In g eneral, the value of k(obs) correlated well with the effective concent ration of free PNO in the CH2Cl2 phase. For the PNO-catalyzed reaction of PhCOCl and CH3COONa in H2O/CH2Cl2 medium, the main conclusions are : (1) The presence of ROH additive in CH2Cl2 increases the distributio n of PNO is CH2Cl2 and the value of k(obs) due to the hydrogen bonding between ROH and PNO. (2) The presence of nonpolar CCl4 and RCOOR' in CH2Cl2 decreases distribution of PNO and the values of k(obs). (3) The presence of RCOOH in CH2Cl2 enchances the distribution of PNO in CH2C l2 and the value of k(obs). However, the main product is PhCOOCOR inst ead of PhCOOCOCH3 in contrast to the cases of adding ROH, CCl4 and RCO OR'. The above results have valuable implication in understanding the inhibitive effect of PhCOCl in the PNO-catalyzed reaction of PhCOCl an d RCOONa in H2O/CH2Cl2 medium.