See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Z-Configuration Analysis **Z-configuration** occurs when the two **highest priority groups on each carbon of a double bond are on the same side**. Use **Cahn-Ingold-Prelog (CIP) rules** to assign priorities: --- ## **(1)** $H_3C\underbrace{>C=C<}_{}\frac{C_2H_5}{H}$ **Left carbon:** $CH_3$ (priority 1) vs $H$ (priority 2) **Right carbon:** $C_2H_5$ (priority 1) vs $H$ (priority 2) Both priority-1 groups ($CH_3$ and $C_2H_5$) are on **opposite sides** → **E-configuration** ✗ --- ## **(2)** $HOCH_2\underbrace{>C=C<}_{}^{Br}\frac{CH(CH_3)_2}{CH_2CH_3}$ **Left carbon:** $HOCH_2$ (priority 1, O has highest atomic number) vs $Br$ (priority 2) **Right carbon:** $CH(CH_3)_2$ (priority 1, C bonded to 3 carbons) vs $CH_2CH_3$ (priority 2) Both priority-1 groups are on the **same side** → **Z-configuration** ✓ --- ## **(3)** $Cl\underbrace{>C=C<}_{Br}^{H}/D$ **Left carbon:** $Cl$ (priority 1) vs $Br$ (priority 2) **Right carbon:** $H$ (priority 2) vs $D$ (priority 1, D = ²H, higher mass number) Both priority-1 groups are on the **same side** → **Z-configuration** ✓ --- **Compounds (2) and (3) have Z-configuration.** The answer is **(4) All the above** only if the question asks which compounds *can* have Z-configuration. However, if strictly asking which *is* Z-configured, **both (2) and (3)** qualify.