The 4-nitrobenzyl ester of acetylphenylhydroxyacetic acid differs in its melting behaviour from other nitrobenzyl esters of
phenylhydroxyacetic or acetylphenylhydroxyacetic acids, the racemate having a higher melting point than the enantiomers. By
means of thermal analysis, IR spectroscopy and X-ray diffractometry the ester can be shown to occur in two crystalline modifications.
In the process of solidification of the molten mass, at first a modification of higher energy is formed, obviously being caused
by an excess of one enantiomer, which is then exothermally rearranged in the lattice of the racemate.