The major product $Z$ obtained in the following reaction scheme is

Identify the compound from the following having the lowest boiling point.

The major product obtained in the following reaction is:

Aniline,when diazotized in cold and then treated with $N,N$-dimethylaniline,gives a coloured product. Its structure would be:

Account for the following:
$(i)$ $pK_{b}$ of aniline is more than that of methylamine.
$(ii)$ Ethylamine is soluble in water whereas aniline is not.
$(iii)$ Methylamine in water reacts with ferric chloride to precipitate hydrated ferric oxide.
$(iv)$ Although amino group is $o-$ and $p-$ directing in aromatic electrophilic substitution reactions,aniline on nitration gives a substantial amount of $m$-nitroaniline.
$(v)$ Aniline does not undergo Friedel-Crafts reaction.
$(vi)$ Diazonium salts of aromatic amines are more stable than those of aliphatic amines.
$(vii)$ Gabriel phthalimide synthesis is preferred for synthesising primary amines.

Identify the correct decreasing order of $pK_b$ values of the following compounds.