Consider the internal alkyne 2-pentyne. When subjected to Birch reduction ( ), it forms Product P. When reduced using Lindlar's catalyst ( ), it forms Product Q. Which of the following correctly ident

Question

Consider the internal alkyne 2-pentyne. When subjected to Birch reduction ( $Na / Liq. NH_3$ ), it forms Product P. When reduced using Lindlar's catalyst ( $H_2 / Pd-BaSO_4$ ), it forms Product Q. Which of the following correctly identifies the specific stereochemistry of P and Q?

Prashant Kotian · Accepted Answer

Correct answer: B. Birch reduction of an internal alkyne proceeds via a single-electron transfer mechanism that involves a radical anion intermediate. Repulsion mandates anti-addition of hydrogen atoms, stereospecifically yielding a -alkene ( -2-pentene). Reduction with Lindlar's catalyst occurs entirely on the surface of the poisoned metal, forcing syn-addition of hydrogen gas and stereospecifically yielding a -alkene ( -2-pentene).

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