How many primary amine isomeric forms are possible for the formula...

The general formula for a primary amine is $\text{R-NH}_2$. For the molecular formula $\text{C}_4\text{H}_{11}\text{N}$, the alkyl group $\text{R}$ is the butyl group, $\text{C}_4\text{H}_9-$.

The butyl group has four structural isomers, which lead to four primary amines:

1. n-butylamine (Bu\tan^{-1}-amine): $\text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{-NH}_2$

2. sec-butylamine (Butan-2-amine): $\text{CH}_3\text{CH}_2\text{CH}(\text{NH}_2)\text{CH}_3$

3. isobutylamine (2-Methylpropan-1-amine): $(\text{CH}_3)_2\text{CHCH}_2\text{-NH}_2$

4. tert-butylamine (2-Methylpropan-2-amine): $(\text{CH}_3)_3\text{C-NH}_2$

Thus, there are 4 primary amine isomeric forms possible for $\text{C}_4\text{H}_{11}\text{N}$.

Answer: $4$