Stilbene/azobenzene units

Spiro Compounds with Stilbene and Azobenzene Units. 112... 

The dominant mechanism of purification for column ciystallization of sohd-solution systems is reciystallization. The rate of mass transfer resulting from reciystallization is related to the concentrations of the solid phase and free hquid which are in intimate contac t. A model based on height-of-transfer-unit (HTU) concepts representing the composition profQe in the purification sec tion for the high-melting component of a binaiy solid-solution system has been reported by Powers et al. (in Zief and Wilcox, op. cit., p. 363) for total-reflux operation. Typical data for the purification of a solid-solution system, azobenzene-stilbene, are shown in Fig. 22-10. The column ciystallizer was operated... 

Azobenzene and stilbene both exemplify this type of crystal. There are four molecules in the cell but they are not all related by symmetry operations. In essence the unit cell consists of two slightly displaced cells of the type in Eq. 10.36. If the molecules are numbered 1, 2, 3, and 4 such that the pairs (1, 2) and (3, 4) are asymmetrically disposed, the unit cell operators transform the sites in the following manner (refer to Eq. 10.56) ... 

---