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Vilsmeier–Haack formylation of coumarin derivatives. A solvent dependent kinetic study
Author(s) -
Rajanna K. C.,
Solomon Florence,
Ali Mir Moazzam,
Prakash P. K. Sai
Publication year - 1996
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(1996)28:12<865::aid-kin1>3.0.co;2-l
Subject(s) - chemistry , solvent , reagent , formylation , solvent effects , adduct , kinetic energy , reaction rate constant , computational chemistry , kinetics , photochemistry , organic chemistry , catalysis , physics , quantum mechanics
A kinetic study of the reaction of coumarin derivatives with Vilsmeier‐Haack (VH) reagent (1:1 DMF‐POCl 3 ) in various solvent media revealed second‐order kinetics with a first‐order in [Substrate] and first‐order in [VH reagent]. The reaction rates altered nonlinearly with an increase in the dielectric constant of the medium and the data did not fit completely well with either Amis or Kirkwood's theories of ion (SINGLEBOND) dipole and dipole (SINGLEBOND) dipole type reactions. On the basis of kinetic and spectroscopic results, participation of VH‐adduct and coumarin molecule in the rate limiting step, has been proposed. Kinetic and activation parameters have been evaluated and discussed in terms of isokinetic relationship and as a function of solvent compositions. Linearity of Leffler's and Exner's plots indicate a similar type of mechanism to be operative in different dielectric media at all temperatures. © 1996 John Wiley & Sons, Inc.