Chemistry – Organic chemistry | e-Consult

The structure of 2-methylpropane (isobutane) is:

(CH₃)₂CHCH₃

Butane has the formula C₄H₁₀ and its structure is CH₃CH₂CH₂CH₃.

2-methylpropane has a lower boiling point than butane because it has a smaller surface area for intermolecular interactions. Both molecules exhibit London Dispersion Forces (LDFs), which are temporary, induced dipoles arising from the random movement of electrons. The strength of LDFs is directly related to the size and number of electrons in a molecule. 2-methylpropane has fewer electrons and a smaller size compared to butane. Therefore, the LDFs between 2-methylpropane molecules are weaker than those between butane molecules. This results in a lower boiling point for 2-methylpropane.

The intermolecular forces present in both molecules are London Dispersion Forces (LDFs). Butane has stronger LDFs due to its larger size and greater number of electrons.