Question

explain the conformations of butane using Newman projections and indicate their relative stability​

Answer 1

Answer:  The Conformational Isomers (and Newman Projections) of Butane

In two previous articles we’ve discussed the conformations of ethane and propane and saw that their staggered conformations were lower in energy than their eclipsed conformations. The barrier to rotation in each (the “torsional strain” of the higher-energy, eclipsed conformation versus the lower-energy eclipsed conformation) was 3.0 kcal/mol in ethane and 3.4 kcal/mol in propane.

In contrast to ethane and propane, which have a single rotational barrier, the situation for butane is a bit more complicated (or as we sometimes say, “more fun”).  The highest energy conformation in butane is about 5 kcal/mol above the lowest-energy conformation. But that’s not the only energy maximum; when rotated about the C2-C3 axis.

Explanation: