Addition of H_2 to 2-butyne in presence of Lindlar's catalyst . Gives cis-2-butene while with Na/in liq. NH_3 gives trans-2-butene.Why so ? Explain.

Addition of H_2 to 2-butyne in presence of Lindlar's catalyst . Gives

1.	Addition of H_2 to 2-butyne in presence of Lindlar's catalyst . Gives cis-2-butene while with Na/in liq. NH_3 gives trans-2-butene.Why so ? Explain.
Answer» <html><body><p></p>Solution :In presence of Lindlar's catalyst (Pd deposited over `BaSO_4` and partially <a href="https://interviewquestions.tuteehub.com/tag/poisoned-7328856" style="font-weight:bold;" target="_blank" title="Click to know more about POISONED">POISONED</a> by addition of S or quinoline), `H_2` gets first absorbed over the catalyst as H atoms and then transferred to the same face of 2-butyne giving cis-2-butene. <br/> <a href="https://interviewquestions.tuteehub.com/tag/however-1032379" style="font-weight:bold;" target="_blank" title="Click to know more about HOWEVER">HOWEVER</a>, in <a href="https://interviewquestions.tuteehub.com/tag/case-910082" style="font-weight:bold;" target="_blank" title="Click to know more about CASE">CASE</a> of Na in liquid `NH_3`, (Birch <a href="https://interviewquestions.tuteehub.com/tag/reduction-621019" style="font-weight:bold;" target="_blank" title="Click to know more about REDUCTION">REDUCTION</a>), the reduction <a href="https://interviewquestions.tuteehub.com/tag/occurs-1127848" style="font-weight:bold;" target="_blank" title="Click to know more about OCCURS">OCCURS</a> through two electron transfers and two proton transfer giving trans-2-butene .</body></html>