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JEE Main levelSingle correct optionDifficulty 2 of 3ro247

Which pair of reagents converts the alkyne shown into the E alkene and the Z alkene respectively?

ANa, liquid $NH X_{3}$ ; then $H X_{2}$ , Lindlar catalyst (on separate samples)
B $H X_{2}$ , Lindlar catalyst; then Na, liquid $NH X_{3}$
C $H X_{2}$ , Pd/C; then Na, liquid $NH X_{3}$
DNa, liquid $NH X_{3}$ ; then $H X_{2}$ , Pd/C

Answer: A

The compound is hex-2-yne. Dissolving-metal reduction (Na/

NH X_{3}

) gives the E alkene by anti addition; the poisoned Lindlar catalyst gives the Z alkene by syn addition. Pd/C with

H X_{2}

over-reduces to hexane and cannot be the source of either alkene.

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