See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Solution: Isomers of $C_2H_9N$ **Step 1: Determine the structure framework** With molecular formula $C_2H_9N$, we have: - 2 carbons - 9 hydrogens - 1 nitrogen Nitrogen has 3 valence electrons, so it can form 3 bonds and carry 0, 1, or 2 lone pairs depending on its oxidation state. **Step 2: Identify primary amines ($RNH_2$)** Structure: $CH_3-CH_2-NH_2$ (ethylamine) This is the only primary amine possible with $C_2H_9N$. **Count: 1 primary amine** **Step 3: Identify secondary amines ($R_2NH$)** Structure: $CH_3-NH-CH_3$ (dimethylamine) Both carbons attach to nitrogen; remaining sites filled with $H$ atoms. **Count: 1 secondary amine** **Step 4: Identify tertiary amines ($R_3N$)** For a tertiary amine, all three positions on nitrogen must be occupied by carbon-containing groups. With only 2 carbons available, this is impossible. **Count: 0 tertiary amines** **Answer: 1, 2, 1** → **(B)** The correct answer is **(B)** because $C_2H_9N$ allows exactly 1 primary amine, 1 secondary amine, and 0 tertiary amines due to insufficient carbon atoms for tertiary amine formation.