Figure 42
2-(4′-Methoxyphenyl)-1,4-benzoquinone – thermal rearrangement of the metastable yellow polymorph to the stable red polymorph. Left series: A crystal heated at ca 360 K. Photographs were taken at intervals of a few seconds. Note that although there were imperfections in the crystal before reaction began (top photograph), they had no discernible effect on the progress of the reaction. Right series: Reaction of a second crystal at 360 K, showing more clearly the preference for frontal development in the [110] and [10] directions. Reprinted with permission from Desiraju et al. (1977). Copyright 1977 American Chemical Society. |