When alkyl substituted acetylene undergoes addition with hydrogen in presence of Lindlar’s catalyst, the alkene formed is

When an alkyl-substituted acetylene undergoes addition with hydrogen in the presence of Lindlar's catalyst, the alkene formed is cis-alkene.

Here's the step-by-step process:

1. The alkyl-substituted acetylene (alkyne) is exposed to hydrogen gas (H2) in the presence of Lindlar's catalyst. Lindlar's catalyst is a deactivated form of palladium, which is used to catalyze the hydrogenation of alkynes to alkenes.

2. The hydrogen atoms add across the triple bond of the alkyne. However, because Lindlar's catalyst is a poisoned catalyst, it only allows for the addition of one molecule of hydrogen (rather than two, which would result in an alkane).

3. The hydrogen atoms add to the same side of the alkyne due to the nature of the catalyst, resulting in a cis-alkene. This is known as syn addition.

So, the product of this reaction is a cis-alkene.