EFFECTS OF SULFENYL, SULFINYL AND SULFONYL GROUPS ON ACIDITIES AND HOMOLYTIC BOND-DISSOCIATION ENERGIES OF ADJACENT C-H AND N-H BONDS

Acidities and bond dissociation energies (BDEs) of the N-H bond in two phenylsulfenylamides, PhSNHBz and PhSNH-t-Bu, and four phenylsulfenyl anilides, 4-GC(6)H(4)NHSPh, where G = MeO, H, Br and CN, were measured in order to compare the effects of substituents on acidities and BDEs of N-H bonds with those of C-H bonds. The effects of PhS groups on ac idities and BDEs in a series of C-H acids were found to be comparable to those on acidities and BDEs of PhS in a similar series of N-H acids . Comparisons were also made of the effects of changing the oxidation state of sulfur in the series PhS, PhSO and PhSO2 on the acidities and BDEs of adjacent N-H and C-H bonds in weak acids. Hammett-type plots of PKHA values for phenyl benzyl sulfones (4-GC(6)H(4)CH(2)SO(2)Ph) an d phenylsulfenylanilides (4-GC(6)H(4)NHSPh) were linear vs sigma(p)(-) values. A linear plot was obtained and explained for a plot of BDE of the N-H bonds in remotely substituted phenylsulfonylanilides with sig ma(+) values. Plots of BDEs vs E-ox(A(-)) were also linear for 4-subst ituted phenylsulfenylanilides (4-GC(6)H(4)NHSPh), phenylsulfonylanilid es (4-GC(6)H(4)NHSO(2)Ph) and phenyl benzyl sulfones (4-GC(6)H(4)CH(2) SO(2)Ph). (C) 1998 John Wiley & Sons, Ltd.