See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Carbon-Carbon Bond Length in 1,3-Butadiene **Structure Analysis:** The compound is $CH_2=CH-CH=CH_2$ (1,3-butadiene). The bond between $C_2$ and $C_3$ is a single bond connecting two sp² hybridized carbons. **Bond Type Classification:** - $C_1=C_2$: double bond (1.34 Å) - $C_2-C_3$: **single bond** (between sp² carbons) - $C_3=C_4$: double bond (1.34 Å) **Resonance Effect:** The $C_2-C_3$ single bond exhibits **partial double bond character** due to resonance delocalization: $$CH_2=CH-CH=CH_2 \leftrightarrow CH_2-CH=CH-CH_2^+$$ This resonance allows π-electron density to stabilize across the conjugated system, shortening the $C_2-C_3$ bond. **Expected Bond Length:** - Normal C-C single bond (sp³-sp³): ~1.54 Å - Normal C=C double bond (sp²-sp²): ~1.33 Å - $C_2-C_3$ with partial double character: **between 1.33 and 1.54 Å** **Answer: (C)** — The bond length is **less than 1.54 Å and greater than 1.33 Å** due to conjugation effects shortening the single bond while keeping it longer than a pure double bond.