The free-radical reaction of tri-n-butyltin hydride with disulfides

✍ Scribed by J. Spanswick; K. U. Ingold

• Publisher: John Wiley and Sons
• Year: 1970
• Tongue: English
• Weight: 477 KB
• Volume: 2
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550020208

✦ Synopsis

The kinetics and absolute rate constants for the free-radical chain reaction of tri-nbutyltin hydride with di-t-butyl disulfide have been measured in cyclohexane at 30". The rate controlling step for chain propagation involves the cleavage of the disulfide bond by an attacking tributyltin radical. The rate constant for this bimolecular homolytic substitution at sulfur is -8 x lo4 Mole-l sec-'. Chain termination involves the self-reaction of two tributyltin radicals.

The rate constants for attack of tributyltin radicals on some other disulfides and on elemental sulfur have also been measured. The results are compared with literature data for homolytic substitutions on these compounds by a variety of radicals which have their unpaired electron centered on carbon.

* Exceptions to this rule are known, the most noteworthy being substitutions of organoboranes and other organometallic compounds by peroxy radicals 211. * This assumes that the sulfur used by Bartlett and Trifan [I21 was free from thiol groups t The relative reactivity of dibenzyl disulfide towards the polystyryl radical may be significantly which, of course, are very efficient chain transfer agents in polymerizing styrene. over-estimated because of attack on the benzylic hydrogens.