Question:

When 2-butyne is treated with H2/Lindlar's catalyst, compound X is produced as the major product and when treated with Na/liq. NH3 it produces Y as the major product. Which of the following statements is correct ?

Show Hint

Lindlar's catalyst gives syn addition (cis-2-butene) and Na/liq. NH3 gives anti addition (trans-2-butene); cis has a net dipole and a higher boiling point.
Updated On: Nov 11, 2026
  • X will have higher dipole moment and higher boiling point than Y.
  • Y will have higher dipole moment and higher boiling point than X.
  • X will have lower dipole moment and lower boiling point than Y.
  • Y will have higher dipole moment and lower boiling point than X.
Show Solution
collegedunia
Verified By Collegedunia

The Correct Option is A

Solution and Explanation

H2/Lindlar's catalyst reduces the alkyne by syn addition: X = cis-2-butene.
Na/liq. NH3 reduces it by anti addition: Y = trans-2-butene.
In cis-2-butene the two C-CH3 bond dipoles add up (net dipole about 0.33 D); in trans-2-butene they cancel (dipole = 0).
The dipole-dipole attraction gives cis-2-butene the higher boiling point (about 277 K versus 274 K for trans).
So X (cis) has both higher dipole moment and higher boiling point than Y.
Answer: (1) X will have higher dipole moment and higher boiling point than Y.
Was this answer helpful?
0
0