Concept:For geometric (cis-trans) isomerism to exist, the molecule must contain a restricted rotation center (like a double bond), and
each carbon of the double bond must be attached to two
different groups.
Solution:- Let's analyze the options for the capacity to form cis and trans isomers:
- A: \( \text{CH}_2=\text{CH}_2 \) has identical hydrogens on both carbons. No geometric isomerism.
- B: \( \text{CHCl}=\text{CH}_2 \) has two identical hydrogens on one carbon. No geometric isomerism.
- C: 2-butene (\( \text{CH}_3\text{CH}=\text{CHCH}_3 \)). Each double-bonded carbon is attached to one H and one \( \text{CH}_3 \). This satisfies the conditions, allowing it to exist as both cis-2-butene and trans-2-butene.
Why other options are incorrect:The other molecules either lack a double bond entirely (like ethane in D) or have two identical substituent groups on at least one sp² hybridized carbon, making cis-trans arrangements identical.
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