Question

Arrange the following in increasing order of their boiling points.

• A. ${\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_2\mathrm{Br}$
• B. ${\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_2{\mathrm{CH}}_2\mathrm{Br}$
• C. $({\mathrm{CH}}_3{)}_2{\mathrm{CHCH}}_2\mathrm{Br}$
• D. $({\mathrm{CH}}_3{)}_3\mathrm{CBr}$

Answer 1

Boiling point increases as the number of carbon atoms increases in the alkyl halides. The attractions get stronger as the molecules get bigger in size and have more electrons. Boiling point of isomeric halides decrease with increase in branching.
Among (i) 1-bromobutane, (ii) 1-bromo-2-methylpropane and (iii) 2-bromo-2-methylpropane, the boiling point decreases from (i) to (iii).
Thus the order of boiling points is:
$C{H}_{3}C{H}_{2}C{H}_{2}C{H}_{2}Br>(C{H}_3{)}_{2}CHC{H}_{2}Br>(C{H}_3{)}_{3}CBr>C{H}_{3}C{H}_{2}C{H}_{2}Br$