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New kinetic methods. 2. . An indirect measurement of ester formation and hydrolysis rates
Author(s) -
Chandler W. David,
Yan Yongfei,
Lee Donald G.
Publication year - 1992
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.610050609
Subject(s) - chemistry , reaction rate constant , hydrolysis , chromium trioxide , reagent , alcohol , chromic acid , absorbance , chromium , kinetics , reaction rate , allyl alcohol , kinetic energy , inorganic chemistry , organic chemistry , catalysis , chromatography , physics , quantum mechanics
The use of an assistant reagent to monitor spectroscopically the concentration of compounds that lack chromophores is described. It is demonstrated, for example, that the concentration of an aliphatic alcohol (present during acidcatalyzed hydrolysis or esterification reactions) can be monitored continuously by addition of a small amount of chromium trioxide. From a knowledge of the rate law and the rate constants for chromic acid oxidations, − d [CrO 3 ]/d t = k [alcohol] [CrO 3 ], the concentration of alcohol can be determined at any time by monitoring the absorbance of chromic acid at 363 nm. The rate at which the concentration of the alcohol is changing can then be used to calculate rate constants for the corresponding esterification or hydrolysis reactions. Rate constants obtained in this way are compared with those previously obtained by use of direct methods, and the application of this approach to the study of kinetics under conditions not accessible by other methods is illustrated.