Q. 9-9-8 P-c - Organic Chemistry (Mcmurry)

Question

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

(c) 3-Methyl-1-pentene

Step-by-Step Solution

Answer

Lindlar catalyst

It’s the reagent used in the react to convert the akyne to alkene by hydrogenation when 1 equivalent When 2 equivalent is present alkyne convert to alkane.

Formation of cis-3-Heptene

Alkyne hydrogenation to alkene occurs when less active Lindlar catalyst is used which is a finely divided palladium metal with lead acetate and quinoline, an aromatic amine. The hydrogenation occurs with syn stereochemistry

Reaction with lindlar catalyst

When alkyne react with lindlar catalyst then it break the three out of one bond and convert alkyne to alkene by the addition of hydrogen to the atom and form alkene as shown: