Answer
Cycloalkanes are cyclic saturated hydrocarbons with the general formula C$_nH_{2n}$. Therefore, a substance with the formula C$_3H_8$ could not be a cycloalkane, since C$_3H_8$ conforms to the general formula, C$_nH_{2n+2}$, the molecular formula for an alkane. It is, however, too small to be a branched alkane with a methyl group attached to the longest chain. In fact, C$_3H_8$ is propane.
Work Step by Step
Cycloalkanes are cyclic saturated hydrocarbons with the general formula C$_nH_{2n}$. Therefore, a substance with the formula C$_3H_8$ could not be a cycloalkane, since C$_3H_8$ conforms to the general formula, C$_nH_{2n+2}$, the molecular formula for an alkane. It is, however, too small to be a branched alkane with a methyl group attached to the longest chain. In fact, C$_3H_8$ is propane.
