MCAT Organic Chemistry Review 2018-2019

14 .    (2R,3S)-2,3-dihydroxybutanedioic    acid    and (2S,3R)-2,3-dihydroxybutanedioic    acid    are:

I. meso compounds.
II. the same molecule.
III. enantiomers.

(A)  I  only

(B)  III    only

(C)  I  and II  only

(D)  I  and III only

15 .    If  the methyl  groups  of  butane  are 120°    apart,  as  seen    in  a   Newman  projection, this

molecule    is  in  its:

(A)  highest-energy gauche  form.

(B)  lowest-energy  staggered   form.

(C)  middle-energy  eclipsed    form.

(D)  highest-energy eclipsed    form.