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Nucleophilic substitution at the pyridine ring. Kinetics of the reaction of 2‐chloro‐3,5‐dinitropyridine with arylthiolates in methanol
Author(s) -
Hamed Ezzat A.
Publication year - 1997
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/(sici)1097-4601(1997)29:7<515::aid-kin5>3.0.co;2-x
Subject(s) - chemistry , pyridine , methanol , nucleophile , nucleophilic substitution , nucleophilic aromatic substitution , ring (chemistry) , chlorine atom , medicinal chemistry , chlorine , hammett equation , carbon atom , kinetics , computational chemistry , reaction rate constant , stereochemistry , organic chemistry , catalysis , physics , quantum mechanics
The reaction rates of 2‐chloro‐3,5‐dinitropyridine 1 with a series of arylthiolates 2a‐h in methanol have been measured at 25°C. The products are the corresponding 2‐thioaryl‐3,5‐dinitropyridine 3a‐h. Good Hammettcorrelation with ρ value−1.19 was obtained suggesting an elimination‐additionmechanism S N Ar and the formation of Meisenheimer‐like intermediates.Plot of log k 2 vs. p K a values of arylthiols gave straight line with β=0.38indicating that the π‐bond breaking in thepyridine ring is so much advanced over bond making between the nucleophileand the carbon that bears the chlorine atom. Excellent correlation betweenlog k 2 and log K (carbon basicity of arylthiolates) was obtained. © 1997 John Wiley& Sons. Inc. Int J Chem Kinet 29: 515–521, 1997.