Propyne is treated with NaNH2, then with ethanal (CH3CHO), then with aqueous acid to give P. P is hydrogenated with H2 over Lindlar's catalyst to give Q. Q is

JEE Advanced levelSingle correct optionDifficulty 3 of 3hc091

Propyne is treated with $NaNH X_{2}$ , then with ethanal ( $CH X_{3} CHO$ ), then with aqueous acid to give P. P is hydrogenated with $H X_{2}$ over Lindlar's catalyst to give Q. Q is

The propynide ion adds to the carbonyl carbon of ethanal, and protonation gives

CH X_{3} - CH (OH) - C \equiv C - CH X_{3}

, pent-3-yn-2-ol (P). Lindlar reduction is a syn addition of

H X_{2}

that stops at the alkene, giving the cis alkene

CH X_{3} - CH (OH) - CH = CH - CH X_{3}

, (Z)-pent-3-en-2-ol.