Describe the following :
(i) Cannizaro reaction
(ii) Decarboxylation

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Solution

(i) Cannizaro reaction:
Aldehydes (not having alpha H atom) undergo self oxidation and reduction (disproportionation) in presence of concentrated aqueous or alcoholic alkali. The products are a mixture of alcohol and salt of carboxylic acid. One aldehyde molecule is reduced to alcohol and other aldehyde molecule is oxidized to salt of carboxylic acid.
Thus when formaldehdye is treated with aq NaOH, a mixture of methyl alcohol and sodium formate is obtained.
$2 H C H O + N a O H \to C H_{3} - O H + H C O O N a$
(ii) Decarboxylation:
When anhydrous sodium salt of carboxylic acid is fused with soda lime (sodium hydroxide and calcium oxide in the ratio 3:1) itgives hydrocarbon containing one carbon atom less than the carboxylic acid. The net result is loss of a molecule of carbon dioxide from carboxylic acid.
$C H_{3} C O O N a + N a O H C a O - - \to Δ C H_{4} + N a_{2} C O_{3}$

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Similar questions

(a) Describe the following:

(i) Acetylation (ii) Cannizzaro reaction

(iii) Cross aldol condensation (iv) Decarboxylation

Describe the following.
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Cannizzaro reaction

Cross aldol condensation

Decarboxylation

C l_{3} C - C O O H

B r_{3} C - C O O H

I_{3} C - C O O H

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