13C NMR spectra and substituent effects of meta and para substituted benzoyl isothiocyanates

Abstract

13C NMR spectra have been studied of 20 meta and para substituted benzoyl isothiocyanates and corresponding benzoyl chlorides. The 13C SCS values of the carbon atom in NCS group have been found to correlate linearly with the Hammet σm,p constants of the substituents as well as with the corresponding π electron charges. The 13C SCS (substituent chemical shift) values of the carbonyl carbon atom of the compounds investigated are little sensitive to substituent effects and are analyzed on the basis of the dual-substituent-parameter approach. Also discussed are the intercorrelation relations of the 13C SCS values of benzoyl isothiocyanates and phenyl isothiocyanates and substituent effects on chemical shifts of carbon atoms of the benzene nucleus. For the benzoyl isothiocyanates the 13C NMR increments of chemical shifts and σm,p substituent constants of CONCS group have been determined.