A bromoalkane '$$X$$' reacts with magnesium in dry ether to form compound '$$Y$$'. The reaction of '$$Y$$' with methanol followed by hydrolysis yield an alcohol having molecular formula, $$\mathrm{C}_4 \mathrm{H}_{10} \mathrm{O}$$. The compound '$$X$$' is

Assertion (A) The boiling points of alkyl halides decrease in the order $$R \mathrm{I}>R \mathrm{Br}>\mathrm{RCl}>\mathrm{RF}$$.

Reason (R) The boiling points of alkyl chlorides, bromides and iodides are considerably higher than that of the hydrocarbon of comparable molecular mass.