Tosylation & Mesylation: Turning Alcohols into Great Leaving Groups

Activate alcohols via tosylation/mesylation. Step-by-step mechanism, why it works, stereochemistry (retention at carbon), and how it unlocks SN2/E2.

• Reaction: Tosylation/Mesylation of alcohols
• What it does: Converts ROH → ROTs/ROMs (better leaving group)
• Typical reagents: TsCl or MsCl + base (pyridine, Et3N)
• Key intermediate: Sulfonate ester (ROTs/ROMs)
• Driving force: Formation of strong S=O bonds; base traps HCl
• Exam type: Synthesis planning
• Exam type: Leaving groups
• Exam type: Choose mechanism