How many chain isomers can be formed by butane? A. One B. Three C. Two D. Four

One
Three
Two
Four

The correct answer is $\boxed{\text{C}}$.

Butane has the molecular formula $C_4H_{10}$. It has two structural isomers, which are different compounds with the same molecular formula but different arrangements of the atoms. The two structural isomers of butane are n-butane and isobutane.

  • n-Butane is the straight-chain isomer of butane. It has the following structural formula:

$$H_3C-CH_2-CH_2-CH_3$$

  • Isobutane is the branched-chain isomer of butane. It has the following structural formula:

$$H_3C-CH(CH_3)-CH_3$$

The two isomers of butane have different physical properties. n-Butane is a gas at room temperature, while isobutane is a liquid. n-Butane has a higher boiling point than isobutane.