Catalytic Hydrolyses of Carboxylic Acid Esters in the Presence of

Hydrolyses of p-nitrophenyl picolinate (PNPP) and p-nitrophenyl acetate (PNPA) mediated by the micellar catalytic systems of two types of cationic surfactants [cetyltrimethylammonium bromide (CTAB), Gemini dimethylene-1,2-bis(cetyltrimethylammonium bromide) (16-2-16, 2Br 2 )] were investigated spectrophotometrically in the pH range of 7.0–9.0 and 258C. Also, the effects of several kinds of additives, such as ethanol, cyclodextrins (CDs), on the hydrolytic reactions of PNPP and PNPA were studied systematically. It is noteworthy that: (1) double chain Gemini surfactant micellar system enhanced the hydrolyses of carboxylic acid esters notably compared with single chain surfactant (CTAB) micellar solutions under the same reaction conditions; (2) the apparent rate constants (kobsd) of PNPP and PNPA hydrolyses increased with the increasing in pH values of reaction media; (3) as additives, ethanol has effect on both PNPP and PNPA hydrolyses, and moreover, the kobsd for hydrolyses decreased with the increasing contents of ethanol ( � 5%) at 258C and pH 9.00; (4) the presence of CDs [a-cyclodextrin (a-CD), b-cyclodextrin (b-CD), g-cyclodextrin (g-CD)], as additives, showed different effects on PNPP and PNPA hydrolyses in different reaction systems.