The crystal structures of two modifications of 2,6-dimethyl-4-(a,a-diphenylmethylene)-1,4-benzoquinone (2,6-dimethylfuchsone) (1) have been determined. One of the forms, (I a), belongs to the space group P2 t/c with a = 8.531 (2), b = 18.677 (5), c = 10.021 (1) A, fl = 90.87 (2) °, Z = 4, and has been refined to an R factor of 0.053 on 1992 non-zero reflections. The other form, (lfl), belongs to the space group P2~2t2 t with a = 8.156 (2), b = 17.761 (4), c = 10.959 (1) A, Z = 4 and has been refined to an R factor of 0.045 on 1452 nonzero reflections. The molecular structures of (1) in the forms (la) and (lfl) are almost identical, and, in the conformation found in the crystal, the molecules exhibit chirality. In both crystals, molecules of the same chirality pack in layers that are almost identical. However, the relationship between adjacent layers is different in the two forms, involving only congruent operations in the (lfl) form, while enantiomorphic operations are involved in the (la) form. Some evidence for a phase transition from the racemic (l a) to the chiral (lfl) is presented. Changes are observed on powder pictures when a ground sample thought to contain (la) and (lfl) is heated to 383 K. These changes can be explained by conversion of (la) to (lfl).
The upper reaches of the Susitna River have been considered for development of a large power-generation system for southcentral Alaska. This report presents a summary and discussion of sediment and hydraulic data obtained from October 1983 to September 1984 at ten sites on the Susitna, Chulitna, Talkeetna, and Yentna Rivers. Sediment data include measurements of suspended-sediment and bedload discharge and analyses of particle-size distribution of suspended sediment, bedload, and bed material; hydraulic data include measurements of width, average depth and velocity, and water-surface slope. Relations between water and sediment discharge are developed for selected sites.
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