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Intramolecular reaction and intramolecular catalysis d̊ II. Mechanism of intramolecular catalysis in hydrolysis of 2‐(2'‐benzimidazolyl)phenyl acetate by benzimidazolyl group
Author(s) -
Xia ChiZhong,
Xia DaoHong
Publication year - 1992
Publication title -
chinese journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.28
H-Index - 41
eISSN - 1614-7065
pISSN - 1001-604X
DOI - 10.1002/cjoc.19920100608
Subject(s) - chemistry , intramolecular force , hydrolysis , catalysis , benzimidazole , yield (engineering) , medicinal chemistry , reaction rate constant , kinetics , buffer solution , reaction mechanism , hydrolysis constant , organic chemistry , materials science , physics , quantum mechanics , metallurgy
As a model for acetyl‐α‐chymotrypsin, 2‐(2'‐benzimidazolyl)phenyl acetate was synthesized in a good yield and its hydrolytic kinetics has been studied in buffer solutions at 45'C within a wide pH range (0.65–8.80). The measured pseudo‐first‐order rate constants ( k obs ) at different pH values conform well with the data derived from the proposed theoretical model. It is shown that in an acidic solution of medium strength (pH = 2.0–3.0), the ester is hydrolyzed via intramolecular general acid catalysis by benzimidazolium cation; while at pH values near neutrality (pH = 5.5–7.0), this ester is hydrolyzed via intramolecular general base catalysis by neutral benzimidazole. These findings are discussed and the activation parameters of the hydrolysis reaction were also determined.