Premium
Effects of non‐ionic and mixed cationic–non‐ionic micelles on the rate of alkaline hydrolysis of phthalimide
Author(s) -
Khan M. Niyaz,
Ismail Emran
Publication year - 2002
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.514
Subject(s) - chemistry , phthalimide , bromide , hydrolysis , aqueous solution , micelle , cationic polymerization , reaction rate constant , alkaline hydrolysis , medicinal chemistry , ionic strength , kinetics , inorganic chemistry , polymer chemistry , organic chemistry , physics , quantum mechanics
Pseudo‐first‐order rate constants ( k obs ) for the alkaline hydrolysis of phthalimide (PTH) show a monotonic decrease with the increase in [C 16 E 20 ] T (total concentration of Brij 58) at constant [CH 3 CN] and [NaOH]. This micellar effect is explained in terms of the pseudophase model of micelles. The rate of hydrolysis of PTH in C 16 E 20 micellar pseudophase appears to be negligible compared with that in the aqueous pseudophase. The values of k obs for C 12 E 23 (Brij 35) show a sharp decrease at very low values of [C 12 E 23 ] T followed by a very slow decrease with increase in [C 12 E 23 ] T at relatively higher values of the latter. The rate of hydrolysis becomes too slow to monitor at [C 12 E 23 ] T ≥0.04 M in the absence of cetyltrimethylammonium bromide (CTABr) and at [C 12 E 23 ] T ≥0.05 M in the presence of 0.006–0.02 M CTABr at 0.02 M NaOH whereas such characteristic behavior is kinetically absent with C 16 E 20 . The values of k obs , obtained at different [NIS] T (where NIS represents C 16 E 20 and C 12 E 23 ) in the presence of a constant amount of CTABr, follow the empirical relationship k obs = ( k 0 + kK [NIS] T )/(1 + K [NIS] T ) where k and K are empirical parameters. The values of k are only slightly affected whereas the values of K decrease with increase in [CTABr] T for the mixed C 16 E 20 –CTABr micellar system. The rate of hydrolysis of PTH at ≥0.01 M C 12 E 23 and ≥0.01 M CTABr reveals the formation of phthalic anhydride whereas this was not observed in the mixed C 16 E 20 –CTABr micellar system under similar experimental conditions. Copyright © 2002 John Wiley & Sons, Ltd.