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15 Apr 2008 19:30:04 IST

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mechanism

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could you please give me the mechanism of thionyl chloride with alkyl halides

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chemicaltester

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15 Apr 2008 19:59:55 IST

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do want mechanism of production of alkyl halide from thionyl and alcohol??

chemicaltester

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15 Apr 2008 20:01:07 IST

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Alcohols will react with Thionyl Chloride to produce alkyl halides. The reaction involves a nucleophilic attack of the alcohol on a Thionyl Chloride molecule displacing one of the Chlorides. Then the chloride will act as the nucleophile in a second step and displace the Oxygen from the carbinol carbon

The HOSOCl decomposes into gaseous Sulfur Dioxide and Hydrogen Chloride.

pardesi .svk

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15 Apr 2008 20:29:07 IST

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no that's not the mechanism actually it proceeds via Sni mechanism with intially the O bonded to the S then back side attck oh cl on c to elminate O

SPARTIAN

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16 Apr 2008 14:42:45 IST

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mr pardesi is right !!!!!!

Madhusudan Chavan

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16 Apr 2008 21:28:20 IST

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The nucleophilic attack of the alcohol molecule on thionyl chloride gives an adduct which subsequently loses a proton and a chloride ion to form alkyl chlorosulphite. This then undergoes another nucleophilic attack by the chloride ion forming an alkyl chloride, SO2 and chloride ion.

R-O-H + S(Cl)(Cl)=O ----> R-O+(H)-S(Cl)(Cl)-O - .......> R-O-S(Cl)(Cl)-O-
R-O-S(Cl)=O
Alkyl chlorosulphite

Cl- + R-O-S(Cl)=O .......> R-Cl + O=S=O + Cl-
The lone pair of electron on oxygen is attacking the sulphur, the sulphur oxygen double bond converts to a single bond, the oxygen of alcohol in the adduct thus carries a positive charge, which the loses a proton and Cl in two subequent steps.
Pyridine catalyses this reaction in the following two ways
1. It neutralises HCl produced in the first step favouring the formation of alkyl chlorosulphite.
2.It helps to pull out Cl- ion from alkyl chlorosulphite thus formed favouring the formation of the products.

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