The reaction of phenyl isothiocyanate with the active methylene reagents 1a–e gives the nonisolable 1:1 adducts 2a–e. The latter react with α‐halogenated compounds, e.g. phenacyl bromide, bromoacetyl bromide, chloroacetone, chloroacetonitrile and some hydrazonoyl halides to give the corresponding polyfunctionally substituted 2,3‐dihydrothiazoles or thiazolidinone ring systems.

The stoichiometry of charge‐transfer complexes which ionise in polar media has been studied by conductimetric titration technique in the systems morpholine‐p‐chloranil (CA), piperidine‐CA and pyrrolidine‐CA in three different polar solvents namely N,N‐dimethylformamide, acetonitrile and dimethylsulfoxide at different temperatures of 10, 15, 18, 20, 25 and 30 °C. The stoichiometric ratios of these complexes were found to vary from 1:1 to 1:4 (acceptor: donor) depending on the system, temperature and solvent used. The ασM‐values of these complexes have been reported. The effect of solvents, temperatures and types of electron donors on the σP‐values has been examined.

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Kinetic studies on the formation of charge transfer complexes of 2-(1H)-pyridinethione with p-acceptors p-chloranil and p-bromanil in dipolar aprotic solvent N,N-dimethylformamide have been carried out spectrophotometrically at various temperatures. The reaction follows an overall third order rate equation, through first order with respect to p-acceptors and second order with respect to the 2-(1H)-pyridinethione. The rates were found to increase with increasing temperature. Activation parameters, DH ¹ and DS ¹ have been calculated for the charge transfer complexes. The structure of the products was confirmed by their elemental analysis, IR, 1 H NMR and mass spectrometry. Conductometric method has been used to investigate the electron donor-acceptor complex formation. The stoichiometries of these complexes have been established and their conductance (s P-) and molar conductivity (sM-) values are reported.

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