Determination of the nucleophilic reactivity constants for a series of N-( n-propyl)- N′-( para- R-benzoyl)thioureas towards trans-[Pt(pyridine) 2Cl 2

Abstract

The relative nucleophilic reaction constants n pt, for a series of N-( n-propyl)- N′-( para- R-benzoyl)thioureas (R=H, CH 3O, (CH 3) 3C, Br, Cl, C 7H 15O, I, NO 2) have been determined for the substrate trans-[PtCl 2(pyridine) 2] in methanol–water (75:25 v/v at 30 °C and μ=0.03), and are compared with that of unsubstituted thiourea. The bimolecular substitution reaction constants k 2 were found to vary from 12.1±1.3 to 6.0±0.4 (for thiourea), corresponding to relative nucleophilicity constants of 4.08–3.78. A small but detectable influence of the substituent has been found on these constants, the n pt values decreasing in the order H∼CH 3O>Cl>C 7H 15O∼t-but∼I>Br>NO 2>thiourea. Essentially however, the nucleophilicity of the series of N-( n-propyl)- N′-( para- R-benzoyl)-thioureas resembles that of thiourea.