Question

Using any alkyne needed, how would you prepare the following alkenes?

(a) trans-2-Octene

Short answer

Alkyne to an alkene uses sodium or lithium metal as the reducing agent in liquid ammonia. This method is complementary to Lindlar’s reduction because it produces trans rather than cis alkenes. Hence we want the trans product so use Li metal.

Step-by-step solution

Formation of trans-2-Octene

Alkyne to an alkene uses sodium or lithium metal as the reducing agent in liquid ammonia. This method is complementary to Lindlar’s reduction because it produces trans rather than cis alkenes. Hence we want the trans product so use Li metal.

Reaction with liquid ammonia

When alkyne reacts with ammonia in the presence of lithium then it breaks the three out of one bond and converts alkyne to an alkene by the addition of hydrogen to the atom but the addition must be in trans relation because of the presence of lithium-ion.