Describe the following
a) Acetylation
b) Cannizaro reaction
c) Cross aldol condensation
d) Decarboxylation

a)Acetylation: Benzene reacts with acetyl chloride in the presence of anhydrous AlCl₃ to form acetophenone.

b) Cannizaro reaction:
Aldehydes which do not contain $\mathrm{\alpha }$ - hydrogens undergo self oxidation and reduction when heated with concentrated alkali (in this reaction one molecule of aldehyde is reduced to alcohol another molecule of aldehyde is oxidized to carboxylicaid)
$\underset{\mathrm{formaldehyde}}{2\mathrm{HCHO}}+\mathrm{NaOH}\to \underset{\mathrm{methanol}}{{\mathrm{CH}}_3\mathrm{OH}}+\underset{\mathrm{sodium} \mathrm{formate}}{\mathrm{HCOONa}}$
c) Cross Aldol condensation:
If Aldol condensation taking place between two different aldehydes or ketones is called cross
aldol condensation.
${\mathrm{CH}}_3\mathrm{CHO}+{\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{CHO}\underset{\mathrm{II}) ∆}{\overset{\mathrm{I}) \mathrm{NaOH}}{\to }}$


d) Decarboxylation: When sodium salt of carboxylic acid is heated with sodalime, decarboxylation takes place (removal of CO₂).
${\mathrm{CH}}_3\mathrm{COONa}+\mathrm{NaOH}\stackrel{\mathrm{CaO}}{\to }{\mathrm{CH}}_4+{\mathrm{Na}}_2{\mathrm{CO}}_3$