Kinetic Study of the Substitution Reactions of Triphenylphosphine with Chlorobenzyl Chlorides, Dimethylbenzyl Chloride, and Methylbenzyl Bromides in Various Two-Phase Organic Solvent/Water Media

Article abstract of DOI:10.1002/jccs.199800077

The kinetics of the substitution reactions of triphenylphosphine (TP) with chlorobenzyl chlorides (CBC), 2,5-dimethylbenzyl chloride (DMBC), and methylbenzyl bromides (MBB) in aprotic organic solvent was studied under the extraction by water. The effects of water, agitation, organic solvent, reactant, and temperature were investigated. These reactions take place via the S_N2 mechanism and exhibit large and negative entropy of activation. The order of relative activity of solvents is CHCl₃ > CH₂Cl₂ >> C₆H₆. In CHCl₃, the order of relative reactivity of benzyl chloride (BC), benzyl bromide (BB), CBC, DMBC, and MBB toward reaction with TP is 2-MBB > 4-MBB > 3-MBB > BB > DMBC > BC > 2-CBC > 4-CBC > 3-CBC. These reactions produce quantitatively benzyltriphenylphosphonium salts, which are useful for synthesizing Z-form isomers of stilbenes via the two-phase Wittig reaction.