On the Mechanism of the Meyer Reaction With Epoxides and 2-Haloalcohols As Substrates^†

Abstract

The Meyer reaction of alkaline arsenious acid with glycidol is first order in As(III) and first order in glycidol. The kinetic and stereochemical evidence shows that the reaction follows an S_N2 mechanism. The uncertainty in the pK ₂ and, especially, pK ₃ values for H₃AsO₃ does not distinguish between HAsO₃ ^2- and AsO₃ ^3- as the actual nucleophile in the Meyer reaction with glycidol as substrate. Kinetic runs and synthetic experiments point towards AsO₃ ^3- as the most probable nucleophile. The Meyer reaction with 3-chloropropane-1,2-diol, proceeds either via glycidol or by direct displacement of chloride, in a ratio determined by the starting stoichiometry. HAsO₃ ^2- does not react with the chlorodiol, thus leaving AsO₃ ^3- as the nucleophile in the Meyer reaction.

Key Words:

• The Meyer reaction
• mechanis
• glycidol
• 3-chloropropane-1,2-diol