Question

By which reagent alkyne converts to cis-alkene?
i.e. $C_6{H}_{11}-C\equiv C-C{H}_3\stackrel{R}{⟶}\text{cis-alkene}$:

• A. $C{r}_2{O}_3/A{l}_2{O}_3$
• B. $H_2,Pd/BaS{O}_4$
• C. $Na/dryether$
• D. $Na/N{H}_3\left(l\right)$

Answer 1

The correct option is B $H_2,Pd/BaS{O}_4$

In presence of lindlar's catalyst, alkynes undergoes partial reduction. the addition of the hydrogen substituent always proceeds via syn addition (addition of the substituent on the same side of the bond). Therefore, the final product is purely cis-isomer of the alkene.