Question

(I) Is it possible to prepare methane by Kolbe’s electrolytic method? 

(II) Explain how 2-butyne reacts with 

(a) Lindlar’s catalyst 

(b) Sodium in liquid ammonia.

Answer 1

(I) Kolbe’s electrolytic method is suitable for the preparation of symmetrical alkanes, that is alkanes containing even number of carbon atoms. Methane has only one carbon, hence it cannot be prepared by Kolbe’s electrolytic method.

(II) 

(a) 2-butyne reacts with Lindlar’s catalyst: 

2- butyne can be reduced to cis – 2 butene using CaCO₃ supported in Pd -metal partially deactivated with sulphur. 

This reaction is stereo specific giving only the cis – 2 – butene.

(b) 2-butyne reacts with sodium in liquid ammonia: 

2-butyne can also be reduced to trans – 2 – butene using sodium in liquid ammonia. This reaction is stereospecific giving only the trans – 2 – butene.