See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

## Solution: C–N Bond Length Order **Step 1: Identify the C–N bond type in each compound** - **I.** Cyclohexene with $NH_2$: C–N is a **single bond** ($sp^2$-C bonded to $sp^3$-N) - **II.** Benzene ring with $NH_2$ and CHO: C–N is a **partial double bond** (resonance in aromatic ring) - **III.** Cyclohexane with $NH_2$: C–N is a **pure single bond** ($sp^3$-C bonded to $sp^3$-N) **Step 2: Analyze bond character and resonance** In compound **II**, the aromatic $NH_2$ group participates in resonance with the benzene ring, donating electron density and creating **partial double bond character**. This increases bond order and **decreases bond length**. **Step 3: Compare single bond lengths** Between pure single bonds (I and III): - **III** ($sp^3$-$sp^3$ single bond): **shortest** among single bonds - **I** ($sp^2$-$sp^3$ single bond): **longer** than III due to $sp^2$ hybridization **Step 4: Order by bond length (longest to shortest)** $$\text{Bond length: III > I > II}$$ Compound III has the longest C–N single bond, compound I has an intermediate single bond, and compound II has the shortest due to partial double bond character from resonance. **The answer is (A): III > I > II**