Write a note on addition compounds of alcohol in aldehyde and ketone. $OR$ What are hemiacetal,acetal and ketal compounds? Give examples.

(N/A) Addition of alcohol to aldehyde compounds:
$(i)$ Hemiacetal: Aldehydes react with one equivalent of monohydric alcohol in the presence of dry hydrogen chloride to yield an alkoxyalcohol intermediate,known as a hemiacetal.
$(ii)$ Acetal: These further react with one more molecule of alcohol to give a gem-dialkoxy compound known as an acetal.
In a hemiacetal,the carbonyl carbon atom is attached to one alkoxy group and one hydroxyl group,whereas in an acetal,the carbonyl carbon atom is attached to two alkoxy groups.
$(b)$ Addition of alcohol to ketone compounds and ketal formation: Ketones react with dihydric alcohols like ethylene glycol under similar conditions to form cyclic products known as ethylene glycol ketals.
$(c)$ Dry hydrogen chloride protonates the oxygen of the carbonyl compounds,thereby increasing the electrophilicity of the carbonyl carbon and facilitating the nucleophilic attack of the alcohol.
$(d)$ Acetals and ketals are hydrolysed with aqueous mineral acids to yield the corresponding aldehydes and ketones,respectively.