Describe the following.
Cross aldol condensation
Acetylation When active hydrogen atom of alcohol phenol or an amine is replaced by acetyl (CH3CO−)group to form corresponding ester or amide, the reaction is known as acetylation. Reagents used are acid chloride or acid anhydride in presence of a base like pyridine or dimethyl aniline.
Cannizzaro reaction Aldehydes which do not have any α-hydrogen atom, undergo self oxidation and reduction (disproportionation) reaction on treating with concentrated alkali.This reaction is called Cannizzaro reaction. As a result, one molecule of aldehyde is reduced to alcohol while another is oxidized to carboxylic acid salt. For example:
Cross aldol condensation When aldol condensation is carried out between two different aldehydes and or ketones, it is called cross aldol condensation. If both the reactants contain α-hydrogen atoms, it gives a mixture of four products. If both the reactants contain α-hydrogens, four compounds are obtained as products. For example, ethanal and propanal react to give four products.
Decarboxylation Carboxylic acids lose carbon dioxide molecule to produce hydrocarbons on heating their sodium salts with sodalime (a mixture of NaOH and CaO in ratio 3:1). This reaction is called decarboxylation.