Compare stability and dihedral angle of ethane using sawhorse and newman projection.

Explanation

Conformations or Ethane: In ethane, the two tetrahedral methyl groups can rotate around the carbon-carbon bond to yield several arrangements. Out of te infinite number of possible isomers two extreme arrangements are called (i) Eclipsed conformation (ii) staggered conformation.
Eclipsed form: In this form, hydrogen atoms of one carbon are eclipsing the hydrogen atoms of the other.
(ii) Staggered form : In this form, the hydrogen atoms of the two carbon atoms are oriented in such a way that they lie far apart from each other. infinite number of other conformations which are in between the eclipsed and staggered conformations are called skew conformations. it may be noted that the eclipsed and staggered forms can be converted into one another by rotation of `60^(@)` about the C - C bond axis. the newman's projection formulas for ethane are given in Fig.
In the the Sawhorse projection formulase, front carbon is shown at the lower end of the line while the rear carbon at the upper end. the lines attached to each carbon are at an angle of `120^(@)`. (The Sawhorse projection formulae of staggered and eclipsed conformations of ethane are given, in Fig.
The staggered conformation of ethane is more stable than other conformations this is because, in staggered conformation as energy associated is minimum, repulsive interactions between the hydrogen atoms attached to the two carbon atoms are minimum due to the maximum distance between them. In eclipsed conformation the energy associated is maximum due to maximum repulsive interactions between the hydrogen atoms attached to the two carbon due to minimum distance between them.