Solution:
Gauch form is more stable than anti when hydrogen bonding is possible between the groups 
The Newmann’s structure of a compound is given as In how many combinations of X and Y the gauche form is more stable than anti? i CH3-CH2-,OHii OH,Fiii NH2,OHiv OH,CH3-CH2- v F, NH2vi NH3,CH3-CH2-vii F,CH3-CH2-viii CH3-CH2-,CH3-CH2- ix H,H
The Newmann’s structure of a compound is given as 
In how many combinations of X and Y the gauche form is more stable than anti?
