Question

Increasing order of stability among the three main conformations (i.e. eclipse, anti, gauche) of 2-fluoroethanol is
(a) eclipse, gauche, anti
(b) gauche, eclipse, anti
(c) eclipse, anti, gauche
(d) anti, gauche, eclipse.

Answer 1

The anti conformation is most stable in which F and OH groups are far apart as possible and minimum repulsion between two groups occurs. In fully eclipsed conformation F and OH groups are so close that the steric strain is maximum, hence this conformation is most unstable. The order of stability of these conformations is anti > gauche > partially eclipsed > fully eclipsed.