The reaction of butanal with n-propylmagnesium bromide gives a:

The major product in the following reaction is:

The major product of the following reaction is:

The reaction that gives the following molecule as the major product is:

The order of ${\mathrm{S}}_{\mathrm{N}}1$ reactivity in aqueous acetic acid solution for the compounds is:

$1$.

$2$. ${\mathrm{H}}_3\mathrm{C}-{\mathrm{CH}}_2-{\mathrm{CH}}_2-\mathrm{Cl}$

$3$. ${\left({\mathrm{H}}_3\mathrm{C}\right)}_3\mathrm{C}-\mathrm{Cl}$ 

Among the compounds $\mathrm{I}-\mathrm{IV}$, the compound having the lowest boiling point is:

The structure of the polymer obtained by the following reaction is: