Amine boranes. III. Propanolysis of pyridine boranes

Article abstract of DOI:10.1021/ic50026a029

The solvolysis kinetics in 1-propanol of a number of alkyl-substituted pyridine boranes was studied. The reactions were first order in amine borane. Linear variation of log k with pK_a of the pyridinium ion was observed for groups of compounds with the same ortho substituents; steric enhancement of rate was attributed to 1.1 and 3.5 kcal./mole of strain relief in the transition state for one or two o-methyl groups, respectively. It was concluded that the solvolysis mechanism involves B-N cleavage in the slow step. It was found that the free energy of the transition state referred to the dissociation products was invariant with substitutions on the pyridine ring.