Question

Construct a model of 1,2-dibromoethane. Draw all of the Newman projections for the staggered and eclipsed conformations. Indicate the most and least stable conformers. What is the cause of this stability/instability? Is it possible to isolate these conformational isomers at room temperature?

Answer 1

Answer.

There are 3 eclipsed and 3 staggered conformations for 1,2-dibromoethane. They are

(a), (b), and (c) are eclipsed conformations and (d), (e), and (f) are staggered conformations of 1,2-dibromoethane.

The most stable conformer is (e) i.e. fully stagerred form. It is because the bromine atoms are opposite each other which leads to minimal steric hindrance.

The most unstable conformer is (a) i.e. fully eclipsed form. It is because the bromine atoms are at minimum distance in this conformation which increases the steric hindrance to maximum and decreases the stability to minimum.

Pure conformational isomers are impossible to isolate at room temperature. The energy difference between these conformers is not considerably high. The energy provided at the room temperature is enough for their interconversions and hence, it is not possible to isolate them at room temperature.