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Synthesis, kinetics, and mechanism of bromophenols by N ‐bromophthalimide in aqueous acetic acid
Author(s) -
Anjaiah Birla,
Prameela Kethavath,
Srinivas Pabba,
Rajanna Kamatala Chinna
Publication year - 2018
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.21214
Subject(s) - chemistry , acetic acid , hammett equation , halogenation , aqueous solution , kinetics , phenol , reaction rate constant , electrophile , electrophilic substitution , entropy of activation , transition state , medicinal chemistry , phenols , kinetic energy , computational chemistry , organic chemistry , catalysis , physics , quantum mechanics
The kinetics and mechanism of bromination of phenol and its substituents, viz. 4‐chlorophenol, 4‐bromophenol, 4‐methylphenol, and 4‐methoxyphenol by N ‐bromophthalimide (NBP) in the presence of mercuric acetate in the temperature range of 303–318 K in aqueous acetic acid medium have been investigated. The reaction follows first‐order dependence on [NBP] and fractional order dependence of rate on [Phenol]. The activation parameters have been evaluated, and based on the observed kinetic results the probable mechanism has been proposed. Observed kinetic features and Hammett's reaction constant (ρ) suggests that bromination occurs through electrophilic substitution of bromonium ion (Br + ) into the aromatic ring in the transition state. Large negative entropy of activation values probably suggests the rigid nature of transition state.