ON THE THERMAL-BEHAVIOR OF ACETYLPHENYLHYDROXYACETIC ACID-4-NITROBENZYL ESTERS

The 4-nitrobenzyl eater of acetylphenylhydroxyacetic acid differs in i ts melting behaviour from other nitrobenzyl esters of phenylhydroxyace tic or acetylphenylhydroxyacetic acids, the racemate having a higher m elting point than the enantiomers. By means of thermal analysis, IR sp ectroscopy and X-ray diffractometry the ester can be shown to occur in two crystalline modifications. In the process of solidification of th e molten mass, at first a modification of higher energy is formed, obv iously being caused by an excess of one enantiomer, which is then exot hermally rearranged in the lattice of the racemate.