Chapter 5, Problem 52P

Tartaric acid $\left[H{O}_{2}CCH\left(OH\right)CH\left(OH\right)C{O}_{2}H\right]$ was an important compound in the history of stereochemistry. Two naturally occurring forms of tartaric acid arc optically inactive. One optically inactive form has a melting point of 210-212 °C, the ocher a melting point of 140°C. The Inactive tartaric acid with a melting point of 210-212°C can be separated into two optically active forms of tartaric acid with the same melting point (16S-170°C). One optically active tartaric acid has ${\left[\alpha \right]}_D^{25}=+12$, and the other, ${\left[\alpha \right]}_D^{25}=-12$. All attempts to separate the other inactive tartaric acid (melting point 140°C) into optically active compounds fail.

(a) Write the three-dimensional structure of the tartaric acid with melting point 140°C.

(b) Write structures for the optically active tartaric acids with melting points of 168-170°C.

(c) Can you determine from the formulas which tartaric acid in (b) has a positive rotation and which has a negative rotation?

(d) What is the nature of the form of tartaric acid with a melting point of 210-212°C?