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Kinetics of the Anaerobic Reaction of para ‐Substituted Phenols with Nitrogen Dioxide
Author(s) -
Reyes Jael,
Lissi Eduardo,
LópezAlarcón Camilo,
Rubio María A.
Publication year - 2017
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.21054
Subject(s) - chemistry , phenols , phenol , protonation , inorganic chemistry , dissociation (chemistry) , aqueous solution , nitrogen dioxide , reaction rate , nitration , organic chemistry , ion , catalysis
ABSTRACT para ‐Substituted phenols in aqueous solution under anaerobic conditions readily react with nitrogen dioxide (NO 2 ● ) over a wide range of experimental conditions. The rate and rate law of the process were dependent on phenol concentration and solution pH. The kinetic order in phenol changed from one (low concentration) to zero (high concentration), a result attributable to total NO 2 ● capture. Initial consumption rate ( r 0 ) of phenols versus pH plots showed parabolic behavior with a minimum rate at pH ca. 5. On the other hand, the maximum rate took place at high pH (pH>10) and involved the protonated phenols. The reaction rate of para‐substituted phenols with NO 2 ● correlated with the bond dissociation energy and with Hammett's parameter. Based on such results and also supported by analysis of products carried out by HPLC‐MS/MS, our data conclusively show that, in spite of the fast acid–base interchanges of phenols and the interconversion of the different nitrogen oxides, the mechanisms of phenols nitration mediated by NO 2 ● or HONO are clearly different.