See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Hyperconjugation Analysis **Hyperconjugation** is the stabilization of a carbocation, alkene, or other electron-deficient species through donation of electron density from a neighboring $\sigma$ bond (typically C–H) into an adjacent p-orbital or π-system. ## Examining Each Compound: **(1) Phenol:** $C_6H_5-OH$ - The aromatic ring is already stabilized by resonance. While the O–H bond can participate in some hyperconjugation, this is not the primary stabilizing effect. **(2) Ethyne:** $HC \equiv CH$ - Triple bond is sp-hybridized with very high electron density in the π-system. No electron-deficient site exists to accept hyperconjugative donation. **No hyperconjugation.** **(3) Ethanol:** $CH_3-CH_2-OH$ - Saturated alcohol. No π-system or carbocation present. C–H bonds cannot donate into a full C–C σ-bond. **No hyperconjugation.** **(4) Propene:** $CH_2=CH-CH_3$ - The π-electrons of $C=C$ constitute an electron-deficient region. The C–H bonds of the adjacent methyl group ($CH_3$) can donate electron density into the π* orbital of the double bond, stabilizing it. - This is **classic hyperconjugation** of an alkene with alkyl substituents. ## Conclusion: **Option (4) Propene** exhibits hyperconjugation through donation from the methyl C–H σ-bonds into the π-system of the double bond.