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Alcohols, Phenols and Ethers
Reactions Involving Cleavage of C–O Bond
1 question from 1 paper, each with its answer.
- question
- 1
- paper
- 1
- of Alcohols, Phenols and Ethers
- 1.54%
Concepts tested
- PCl5 replaces OH by Cl
All Questions
2004 AIPMT 1 question
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The –OH group of an alcohol or the carboxylic acid can be replaced by –Cl, using :-Phosphorus pentachloride reacts with both alcohols and carboxylic acids, replacing the –OH group by –Cl:
$R-OH + PCl_5 \rightarrow R-Cl + POCl_3 + HCl$
$R-COOH + PCl_5 \rightarrow R-COCl + POCl_3 + HCl$ (acid chloride)
Hydrochloric acid converts alcohols to alkyl chlorides (with $ZnCl_2$, Lucas reagent) but it cannot convert a carboxylic acid into an acid chloride. Chlorine and hypochlorous acid do not replace –OH by –Cl.
So the reagent is phosphorus pentachloride, $PCl_5$ (also used to test for an –OH group, since HCl fumes are given off).