PSEUDOHALOGEN CHEMISTRY—X STERIC EFFECTS IN THE HOMOLYTIC ADDITION OF THIOCYANOGEN TO ALKENES

Abstract

Homolytic addition of thiocyanogen to alkenes with at least three methyl groups or two phenyl groups on the double bond gives vicinal dithiocyanates and/or thiocyanato-isothiocyanates. The addition to (E)- and (Z)- PhCH=CHPh is non-stereospecific, but the thiocyanato-isothiocyanates derived from unsymmetrical alkenes are formed regiospecifically with the isothiocyanato group being attached to the more heavily substituted C atom. A radical-chain mechanism, involving competing kinetically-controlled chain transfer at the S atom and sterically-controlled chain transfer at the N atom of the thiocyanogen molecule, is proposed.

Key Words:

• Steric effects
• homolytic addition
• thiocyanogen
• alkenes