Consider the following reaction sequences and choose the correct option.
Detailed Solution
Step 1: Analyze the Formation of K and L
The starting reactant is 1-phenylprop-1-yne (Ph-C≡C-Me). When this alkyne is treated with H2 and Lindlar's Catalyst, it undergoes syn-addition to yield product K, which is cis-1-phenylprop-1-ene. Conversely, when treated with Na/liq. NH3 (dissolving metal reduction), it undergoes anti-addition to yield product L, which is trans-1-phenylprop-1-ene.
Step 2: Evaluate Isomerism of K and L
Because product K is the cis-isomer and product L is the trans-isomer of the exact same alkene (1-phenylprop-1-ene), they differ strictly in the spatial arrangement of their groups across the carbon-carbon double bond. Therefore, K and L are geometrical isomers.
Step 3: Verify M and N (For Completeness)
Reacting K with HBr follows Markovnikov's rule to form 1-bromo-1-phenylpropane (M). Reacting L with HBr in the presence of benzoyl peroxide triggers the Anti-Markovnikov (Kharasch) effect, forming 2-bromo-1-phenylpropane (N). Since M and N have different atomic connectivities, they are structural (positional) isomers, not stereoisomers. This confirms the relationship between K and L is the only correct statement.
Final Answer: (B) K and L are geometrical isomers
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