Advices For Studying Organic Chemistry

+ OCH 2 CH 3

Ethyl

ethyl

H (−baseHCl) OCH 2 CH 3

p-Toluenesulfonyl

chloride

Ethanol p-toluenesulfonate

( tosylate)

S

O

O

S CH 3

O

Cl

O

CH 3

2. The mechanism for the sulfonation of alcohols:

A Mechanism for the Reaction

Conversion of an Alcohol into an Alkyl Methanesulfonate

O−

S

O Cl

O

R

O R + O

R

+

O R

Me

H

Alcohol

The alcohol oxygen attacks the

sulfur atom of the sulfonyl chloride.

The intermediate

loses a chloride ion.

Alkyl methanesulfonate

Loss of a proton leads

to the product.

+

+ H

Methanesulfonyl

chloride

S

O

CH 3 Cl

O

O

S

O

Me

H

− B

O

S

O

Me H B

3. Sulfonyl chlorides are usually prepared by treating sulfonic acids with phosphorus
   pentachloride.

+

p-Toluenedulfonic

acid

p-toluenesulfonyl chloride

(tosyl chloride)

S

O

OH POCl 3 Cl

O

CH 3 S + +H

O

Cl

O

PCl 5 CH 3

4. Abbreviations for methanesulfonyl chloride and p-toluenesulfonyl chloride are
   “mesyl chloride” and “tosyl chloride”, respectively.

1. Methanesulfonyl group is called a “mesyl” group and p-toluenesulfonyl group is