The conversion of ethyl alcohol to acetaldehyde is an example of what?

An organic compound $X$ on treatment with $PCC$ in dichloromethane gives the compound $Y$. Compound $Y$ reacts with $I_{2}$ and alkali to form a yellow precipitate of triiodomethane. The compound $X$ is

In esterification,the reactivity of alcohols is:

Explain the effects and remedies when an alcoholic consumes denatured alcohol.

Identify $A$ in the given reaction.

Which of the following compounds are not oxidized by $HIO_4$?
$(1)$ $CH_3-CH(OH)-CH_2-OH$
$(2)$ $CH_3-C(=O)-CHO$
$(3)$ $CH_3-C(=O)-C(=O)-CH_3$
$(4)$ $CH_3-C(=O)-CH(NH_2)-CH_3$
$(5)$ Cyclohexene oxide
$(6)$ $CH_3-O-CH_2-CH_2-OH$
$(7)$ $HOOC-CH_2-OH$