The minimum no of Carbon atoms an alkyne must have to show diastereomerism a) 4 b) 5 c) 6 d) 7

The minimum number of carbon atoms an alkyne must have to show diastereomerism is 4.

Here's why:

Diastereomerism is a type of stereoisomerism. It is the phenomenon where two or more stereoisomers of a compound have different configurations at one or more (but not all) of the equivalent (related) stereocenters and are not mirror images of each other.

In the case of alkynes, they can show diastereomerism when they have two stereocenters. A molecule needs at least two stereocenters to show diastereomerism.

In alkynes, a stereocenter is a carbon atom bonded to four different groups. In the simplest alkyne (ethyne or acetylene), there are only two carbon atoms, and each is bonded to only one other kind of atom, so there are no stereocenters.

The next simplest alkyne (propyne) has three carbon atoms, but again, each carbon is bonded to at most two kinds of atoms, so there are no stereocenters.

Butyne, with four carbon atoms, can have a stereocenter: the two central carbon atoms can each be bonded to three different kinds of atoms (a hydrogen, a methyl group, and an ethyl group). So, butyne and larger alkynes can show diastereomerism.

So, the answer is a) 4.