Question

Arrange the melting points of following compounds in decreasing order

$1.$ n-butane

$2.$ cis-2-butene

$3.$ trans-2-butene

$4.$ 1-butyne

• A. 1 > 2 > 3 > 4
• B. 4 > 2 > 3 > 1
• C. 4 > 3 > 2 > 1
• D. 3 > 2 > 1 > 4

Answer 1

Answer: (C)

Melting point $\propto$ molecular weight, symmetry of the molecule

$\propto \frac{1}{\mu }$ of the compound. $\left(\text{μ}=\text{dipole}\text{moment}\right)$

Hence the correct order of melting point is

1-butyne > trans-2-butene > cis-2-butene > n-butane.