Consider the stereochemistry of addition reactions to alkynes and alkenes. Which of the following st — Hydrocarbons Chemistry Question

💡 Solution & Explanation

(A) and (B) are the classic complementary stereoselective reductions for alkynes. (D) Halogenation involves a bridged halonium ion, forcing the incoming nucleophile to attack from the opposite face (anti-addition). (C) is incorrect; reaction with cold dilute $KMnO_4$ or $OsO_4$ proceeds via a cyclic intermediate, resulting in strictly syn-hydroxylation (forming a *cis*-diol).