Formation of tosylates from alcohols
Description: Treatment of alcohols with p-toluenesulfonyl chloride (TsCl) results in the formation of tosylates, which is an excellent leaving group.
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Notes: Sometimes a base such as pyridine is added to this reaction to neutralize the HCl that is formed. The tosylates formed can be used in subsequent substitution or elimination reactions.
Examples:
Notes: The fourth example shows pyridine (a base) being used.
Mechanism: Tosylation of alcohols begins with nucleophilic addition to the sulfur (Step 1, arrows A and B). The Cl is then expelled in a 1,2-elimination reaction (Step 2, arrows C and D). Finally the positively charged oxygen is deprotonated (Step 3, arrows E and F).
Notes: It’s also reasonable to show a proton transfer after step 1, followed by elimination. Alternatively, another equivalent of alcohol could act as the base in step 3 instead of Cl.
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{ 4 comments… read them below or add one }
it’s excellent……..
Excellent. I was reading Kaplan MCAT review and messed up with this reaction. This page gives clarity of thought that may be needed to do good on MCAT….
Is this reaction possible if Methyl group were not there on the benzene ring?
Yes, except it wouldn’t be tosylate, it benzenesulfonyl.