THE ROLE OF POWDER DIFFRACTION IN ESTABLISHING STRUCTURE-PROPERTY RELATIONSHIPS FOR CRYSTALLINE SOLIDS - A NEW STRUCTURAL ASSIGNMENT OF THEPHOTOREACTIVE AND PHOTOSTABLE PHASES OF P-FORMYL-TRANS-CINNAMIC ACID

It has been reported previously that the photoreactive beta phase of p -formyl-trans-cinnamic acid represents an exception to the well-establ ished correlation between structural and photochemical properties of c rystalline trans-cinnamic acid derivatives. However, it is shown in th is paper that the crystal structure reported previously to be the beta phase of p-formyl-trans-cinnamic acid is actually the photostable gam ma phase. In a wider context, the work reported here highlights the ne cessity of carrying out powder diffraction investigations in the deter mination of structure-property relationships for crystalline solids.