Question

The formation of (B) and (D) takes place, respectively, when :

• A. The formation of (B) occurs by anti- and (D) by syn-addition of $H_2$
• B. The formation of (B) occurs by syn- and (D) by anti-addition of $H_2$
• C. The formation of both takes place by syn-addition of $H_2$
• D. The formation of both takes place by anti-addition of $H_2$

Answer 1

The correct option is B The formation of (B) occurs by syn- and (D) by anti-addition of $H_2$

The compound (B) is cis-But-2-ene and the compound (C) is trans-But-2-ene. Both compounds are obtained by addition of molecule of hydrogen to $C\equiv C$ triple bond. The formation of (B) occurs by syn- and (D) by anti-addition of $H_2$.