A new form of resorcinol. I. Structure determination by X-rays

At about 74º C. ordinary resorcinol (α-resorcinol) undergoes a transformation into a denser crystalline modification, called β-resorcinol (Ubbelohde and Robertson 1937), and a comparison of these two structures is of considerable general interest for the problem of intermolecular bonding in hydroxylic compounds. The crystalline structure of α-resorcinol has already been fully determined (Robertson 1936), and the present paper gives a corresponding X-ray determination of the structure of β-resorcinol. The comparatively open structure of α-resorcinol, which is apparently maintained by the directive power of the hydroxyl bonds, is replaced in β-resorcinol by a more parallel and compact arrangement of the molecules, reminiscent of many hydrocarbon structures. Several different factors are involved in this transformation, and it is accompanied by some deformation of the resorcinol molecule. The results are discussed more fully in relation to the thermodynamic properties of resorcinol in the following paper (Part II).