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Kinetics of base‐catalysed ring closure of methyl 2,6‐dinitrophenylsulfanylethanoate
Author(s) -
Janík Marek,
Štěrba Vojeslav,
Černý Jiří,
Macháček Vladimír,
Jansa Petr
Publication year - 2005
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.949
Subject(s) - chemistry , thiazole , ring (chemistry) , base (topology) , kinetics , chloride , reaction rate constant , ionic strength , medicinal chemistry , conjugated system , stereochemistry , organic chemistry , aqueous solution , mathematical analysis , physics , mathematics , quantum mechanics , polymer
The base‐catalysed ring closure of methyl 2,6‐dinitrophenylsulfanylethanoate gives 2‐methoxycarbonyl‐7‐nitrobenzo[ d ]thiazole‐3‐oxide. The kinetics of this ring closure were studied by means of UV–visible spectrophotometry in methanolic buffers of N ‐methylmorpholine– N ‐methylmorpholinium chloride and N ‐methylpiperidine– N ‐methylpiperidinium chloride at 25°C at ionic strength I = 0.1 mol l −1 . The dependences of k obs on the base concentration are not linear, their slopes decreasing with increasing base concentration at constant ratio of the buffer components. The reaction mechanism was suggested on the basis of comparison with the ring closure kinetics of methyl 2,4,6‐trinitrophenylsulfanylethanoate. The rate‐limiting step of the reaction sequence consists in formation of the conjugated base of substrate 1 . Copyright © 2005 John Wiley & Sons, Ltd.