Construct sawhorse and Newman projections (Sec. 2.3A) of the three staggered conformations of 2-methylbutane (isopentane) that result from rotation about the C2—C3 bond.

(a) Identify the conformations that are chiral.

(b) Explain why 2-methylbutane is not a chiral compound, even though it has chiral conformations.

(c) Suppose each of the three conformations in part (a) could be isolated and their heats of formation determined.

Rank these isomers in order of increasing heat of formation (that is, smallest first). Explain your choice. Indicate whether the ΔH°_f values for any of the isomers are equal and why.