Question

When 2-butyne is treated with $H_2/\text{Lindlar's}$ catalyst, compound X is produced as the major product and when treated with Na/liq. $N{H}_3$ it produces Y as the major product. Which of the following statements is correct?

• A. Y will have higher dipole moment and lower boiling point than X
• B. X will have higher dipole moment and higher boiling point than Y
• C. Y will have higher dipole moment and higher boiling point than X
• D. X will have lower dipole moment and lower boiling point than Y

Answer 1

The correct option is B X will have higher dipole moment and higher boiling point than Y

When 2-butyne is treated with $H_2/Lindla{r}^{\prime }s$ catalyst, compound X (cis-2-butene) is produced as the major product; and when treated with Na/liq $N{H}_3$ it produce Y (trans-2-butene) as the major product.

Cis-isomers have higher dipole moment than trans because in cis isomers similar groups are at same direction whereas in trans they are at opposite direction.
Due to higher dipole moment, cis isomer will have higher boiling point than trans.

Hence, option (d) is correct.