ISSN:
0021-8383
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The kinetics of azocoupling between 1-benzyl-4-phenyl-, 1,3,4-triphenyl-, 4-benzyl-1-methyl-, 1,4-dimethyl-, 1,4-diphenyl-3-methylmercapto- and 3-benzyl-mercapto-1,4-diphenyl-1,2,4-triazolium salts, and p-N,N-dimethylamino benzenediazonium tetrafluoroborate are studied spectroscopically in methanol/water 1:1 (v/v) at various pH values following up the growing-in of the respective azodyes.The competing reactions of the diazonium salt with the solvent and the buffer (NH3/NH4Cl), and of some bleaching of the azodye formed were studied separately and accounted for in the kinetic treatment.From the pH dependence of the coupling rate constants and by application of kinetic models it turned out that not the widely accepted one-step deprotonation mechanism of the quaternary triazolium salts applied but a two-step mechanism comprising of pseudobase formation and their subsequent deprotonation is valid.Using the pertinent kinetic model the pK values of pseudo-base formation (pKR+) and their deprotonation (pKA) were determined by non-linear regression.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/prac.19913330102
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