PBr₃: Converting Alcohols to Alkyl Bromides (SN2 Inversion)

Master the PBr3 mechanism for converting alcohols into alkyl bromides. Phosphite intermediate, SN2 inversion, and how to avoid rearrangements.

• Reaction: ROH → RBr (PBr3)
• What it does: Replaces –OH with –Br (good for 1°/2° alcohols)
• Typical reagents: PBr3, often with base present (or generated Br−)
• Key intermediate: Alkyl phosphite (RO–PBr2) + Br−
• Driving force: Formation of strong P=O in workup; Br− is good nucleophile
• Exam type: Stereochemistry
• Exam type: Predict product
• Exam type: Reagent selection