Stereoisomers are the isomers that have different geometrical arrangement of bonds in space but the same composition. Conformation is a property in which rotation of groups about a bond takes place due to which different spatial arrangements arise. Conformation isomers are a type of stereoisomers in which we can convert one isomers to another one, just by rotating it around a single bond. Now let us understand it with the help of an example:
Take the structure of butane and draw its Newman projection. We will get the structure as given below:
It has two substituents i.e. methyl groups attached to the two end carbon atoms. Methyl group is comparatively larger than hydrogen atoms. Everything on the front side is eclipsing the structure in the backside when looked at from any one carbon atom to the other. One methyl group is just in front of the other methyl group, and the other hydrogen atoms are kept just at the back of other hydrogen atoms. So this structure is completely eclipsing i.e. they are fully eclipsed. This conformational isomer of butane is known as Syn conformation. Now if we rotate the front methyl group by \(60^\circ \)
Which of the following will be the most stable conformation?
Observe the last diagram in the figure. This is anti conformation. In this, the dihedral angle is \(180^\circ \)
Stability of conformation of isomers:
Anti > Gauche > Eclipsed(not fully) > Eclipsed or syn(fully eclipsed)
We can also have the sawhorse projection.
Watch the video to know more about Conformational Stereoisomerism in detail.