91Ó°ÊÓ

Alkynes get converted to alkenes in the presence of hydrogen and Lindlar’s catalyst. The alkenes are further converted to alcohols by treating with ozone, zinc and\({{\bf{H}}_{\bf{3}}}{{\bf{O}}^{\bf{ + }}}\).

(a)The given reaction shows the conversion of 1-pentyne to butanal. The reactant, 1-pentyne can be treated with \({{\rm{H}}_{\rm{2}}}\) and Lindlar’s catalyst to produce 1-pentene. This further reacts with \({{\rm{O}}_{\rm{3}}}\) , zinc and acetic acid to produce butanal. The reaction can be given as:

Reaction (a)

(b)The reaction shows the conversion of 4-methyl-1-pentyne to trans-6-methyl-3-heptene.In the first step, the lower alkyne, 4-methyl-1-pentyne is converted to a higher alkyne, 6-methyl-hept-3-yne by reacting with\({\rm{NaN}}{{\rm{H}}_{\rm{2}}}\)in liquid ammonia and\({\rm{C}}{{\rm{H}}_{\rm{3}}}{\rm{C}}{{\rm{H}}_{\rm{2}}}{\rm{Br}}\). The resultant alkyne further reacts with Li in ammonia to produce trans-6-methyl-3-heptene. The reaction can be given as:

Reaction (b)