Tartaric acid, 2,3-dihydroxybutanedioic acid, can come in three different forms, corresponding to the models assembled in 2a-o: a pair of optically active enantiomers and a third optically inactive form called the meso form. The latter is a diastereomer of the optically active enantiomers.
Tartaric acid
p. Draw solid/dashed-wedge structures for the three tartaric acid forms. Label enantiomers, diastereomers, and the meso form.