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4‐Alkylbenzopyrylium perchlorates as C—H Acidic compounds
Author(s) -
Grummt U.W.,
Czerney P.
Publication year - 2002
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.515
Subject(s) - chemistry , deprotonation , protonation , substituent , carbocation , alkyl , kinetics , medicinal chemistry , proton , ab initio , computational chemistry , organic chemistry , ion , physics , quantum mechanics
7‐Alkyl‐5,6‐dihydro‐3‐methoxy(naphtho[1,2 b ]‐1‐benzopyrylium) compounds are acidochromic due to CH acidity of the 7‐alkyl substituent. Their acidity exponents are 4 < p K a < 5 and 1 < p K a < 3 regardless of whether the carbocation generated by deprotonation is resonance stabilized by a phenyl substituent or not. The thermodynamic equilibrium data were obtained via UV–vis spectroscopy. The activation parameters for protonation and deprotonation reactions were derived from rapid mixing experiments. Ab initio calculations with model compounds are presented in order to rationalize the experimental findings. The title compounds are useful objects to study the kinetics of proton‐transfer kinetics to and from carbon. Copyright © 2002 John Wiley & Sons, Ltd.