Question

Arrange the above compounds in increasing order of their boiling points:

• A. $ii>i>iii$
• B. $i>ii>iii$
• C. $i>iii>ii$
• D. $iii>ii>i$

Answer 1

The correct option is B $i>ii>iii$

More is the molecular size, more is the intermolecular forces of attractions.​ So, large amount​ of heat require to break strong intermolecular forces​ and thus boiling point increases. Here, the molecular size of $\left(i\right)$ and $\left(ii\right)$ is greater than $\left(iii\right)$.
So, the boiling point of $\left(i\right)$ and $\left(ii\right)$ is greater than $\left(iii\right)$.
Now comparing $\left(i\right)$ and $\left(ii\right)$, boiling point of isomeric​ haloalkanes decreases with increase in branching. So boiling point of $\left(ii\right)$ is less than $\left(i\right)$ as former is more branched.
Hence, the overall boiling point order is $i>ii>iii$.