°,RH S,2 reaction mechanisms are also involved in two common procedures which can be utilized to prepare alky l halides from alcohols; that is reaction with PBr and with SoClz In the reaction with PBr,, an intermediate phosphite ester is formed, which undergoes S,2 displacement with bromide anion to give the alkyl bromide with inversion of configuration Br3 a phosphite ester Thiony l chloride reacts by a similar mechanism involving a sulfite ester in polar solvents (i.e, pyridine), but can undergo an unusual S i mechanism in non-polar solvents (benzene) to give the alkyl chloride with retention of configuration (this involves an unusual frontside attack, but is worth remembering since the pair of reactions gives you stereochemical control over the generation of an alkyl chloride)SN2 reaction mechanisms are also involved in two common procedures which can be utilized to prepare alkyl halides from alcohols; that is reaction with PBr3 and with SOCl2. In the reaction with PBr3, an intermediate phosphite ester is formed, which undergoes SN2 displacement with bromide anion to give the alkyl bromide with inversion of configuration. Thionyl chloride reacts by a similar mechanism involving a sulfite ester in polar solvents (i.e., pyridine), but can undergo an unusual SNi mechanism in non-polar solvents (benzene) to give the alkyl chloride with retention of configuration (this involves an unusual frontside attack, but is worth remembering since the pair of reactions gives you stereochemical control over the generation of an alkyl chloride)