Question

What is the minimum number of carbon needed to make an optical isomer (alkene)?
(I know the ans is 7 but how is it 7?)

Answer 1

Answer:

Optical isomer is possible if all 4 groups attached to a carbon are different.

Consider a carbon atom.

The first group to be attached can be H (hydrogen atom)

The second group can be a methyl group

The third group can be an ethyl group

The fourth group can be a propyl group

The reason I chose these groups are because they have the minimum number of carbon atoms, and all groups are different. Hence when they are attached to a carbon atom, it satisfies the condition for optical isomerism.

Now to find the number of carbon atoms:

(1 carbon to which the groups are attached) + (1 carbon of methyl) + (2 carbon of ethyl) + (3 carbons of  propyl)

= 1+1+2+3

= 7, which is the answer