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Preparation, Physical and Chemical properties - Acid Halides | 12th Chemistry : UNIT 12 : Carbonyl Compounds and Carboxylic Acids

Chapter: 12th Chemistry : UNIT 12 : Carbonyl Compounds and Carboxylic Acids

Acid Halides

They emit pale fumes of hydrogen chloride when exposed to air on account of their reaction with water vapour.

Acid Halides:


Methods of Preparation of acid chloride:

Acid chlorides are prepared from carboxylic acid by treating it with anyone of the chlorinating agent such as SOCl2, PCl5, or PCl3

1) By reaction with thionyl Chloride (SOCl2)


This method is superior to others as the by products being gases escape leaving the acid chloride in the pure state.

 

Physical properties:

• They emit pale fumes of hydrogen chloride when exposed to air on account of their reaction with water vapour.

• They are insoluble in water but slowly begins to dissolve due to hydrolysis.

 

Chemical properties:

They react with weak nucleophiles such as water, alcohols, ammonia and amines to produce the corresponding acid, ester, amide or substituted amides.

1) Hydrolysis. Acyl halides undergo hydrolysis to form corresponding carboxylic acids


2) Reaction with Alcohols (Alcoholysis) gives esters.


3) Reaction with Ammonia (Ammonolysis) gives acid amides.


4) Reaction with 1º and 2º Amines gives N-alkyl amides.


(5) Reduction.

(a) When reduced with hydrogen in the presence of ‘poisoned’ palladium catalyst, they form aldehydes. This reaction is called Rosenmund reduction. We have already learnt this reaction under the preparation of aldehydes


(b) When reduced with LiAlH4 gives primary alcohols.



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12th Chemistry : UNIT 12 : Carbonyl Compounds and Carboxylic Acids : Acid Halides | Preparation, Physical and Chemical properties


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