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(i) Acetylation
The introduction of an acetyl functional group into anorganic compound is known as acetylation. It is usually carried out in thepresence of a base such as pyridine, dirnethylaniline, etc. This processinvolves the substitution of an acetyl group for an active hydrogen atom.Acetyl chloride and acetic anhydride are commonly used as acetylating agents.
For example, acetylation of ethanol produces ethylacetate.
(ii) Cannizzaro reaction:
The self oxidation-reduction (disproportionation) reactionof aldehydes having no α-hydrogens on treatment with concentrated alkalis isknown as the Cannizzaro reaction. In this reaction, two molecules of aldehydesparticipate where one is reduced to alcohol and the other is oxidized tocarboxylic acid.
For example, when ethanol is treated with concentratedpotassium hydroxide, ethanol and potassium ethanoate are produced.
(iii) Cross-aldol condensation:
When aldol condensation is carried out between twodifferent aldehydes, or two different ketones, or an aldehyde and a ketone,then the reaction is called a cross-aldol condensation. If both the reactantscontain α-hydrogens, four compounds are obtained as products.
For example, ethanal and propanal react to give fourproducts.
(iv) Decarboxylation:
Decarboxylation refers to the reaction in which carboxylicacids lose carbon dioxide to form hydrocarbons when their sodium salts areheated with soda-lime.
Decarboxylation also takes place when aqueous solutions ofalkali metal salts of carboxylic acids are electrolyzed. This electrolyticprocess is known as Kolbe’s electrolysis.