# Stability of Gauche and Anti form in conformational Isomerism

I came through this question: Which form is stable Gauche or Anti in F-CH2-CH2-F? My answer: Due to lone pair repulsion Anti form should be more stable but the answer is given Gauche form. Please tell me how is gauche form more stable in this case?

• in gauche form there is intramolecular hydrogen bonding between H and F which makes it stable... – maverick Oct 3 '20 at 13:58

This problem should be referred to concept called stereoelectronic effect. It is stabilized by the donation of $$\sigma_{C-H}$$ bond to $$\sigma_{C-F}$$ bond, leading to decrease energy of the whole system.