See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Geometrical Isomerism Analysis **Geometrical isomerism** occurs when atoms/groups are fixed in space around a double bond and can exist in distinct spatial arrangements (cis/trans or E/Z). ## Examining Each Option: **(A) Isobutene** $\rightarrow$ $(CH_3)_2C=CH_2$ - The $C=C$ double bond has: two methyl groups on one carbon, and one H and one H on the other carbon - Since two groups on the terminal carbon are identical (both H), **cis-trans isomerism is possible** - ✓ Shows geometric isomerism **(B) Acetone oxime** $\rightarrow$ $(CH_3)_2C=NOH$ - The $C=N$ double bond has: two methyl groups on carbon (identical), and one O and one H on nitrogen (different) - However, the $N-O$ bond can rotate freely due to resonance/tautomerization - ✗ No fixed geometry **(C) Acetophenone oxime** $\rightarrow$ $C_6H_5-C(=NOH)-CH_3$ - The $C=N$ double bond has different groups, BUT the $N-O$ bond exhibits restricted rotation and tautomerization - ✗ No true geometric isomerism **(D) Benzophenone oxime** $\rightarrow$ $(C_6H_5)_2C=NOH$ - Similar to (B) and (C): the oxime $C=N$ bond shows restricted rotation in some cases, but tautomerization complicates true geometric isomerism - ✗ Not clean geometric isomerism **Answer: (A)** — Isobutene has a true $C=C$ double bond with restricted rotation, allowing cis/trans isomers.