Green cation substitution

Barker et al. (1961) found such a correlation for Malachite Green cations. It is not necessary, however, that the acid and conjugate base frequency shifts should separately be related to the substituent a-values in this way for a good correlation to be obtained between a and the difference in their frequency shifts, i.e. the difference in their frequency maxima and hence in p (Sj)—pAT(S0). Figure 10 shows a plot of Av against a for substituted 5-phenylazotropolones, the acid and base forms of which separately showed very erratic... 

Fig. 4 Representative membrane-active peptides that have been studied by solid-state 19F-NMR. (a) The primary sequences show which positions were substituted (filled green boxes) or which ones could in principle be substituted (dotted green lines), (b) Characteristic conformations of the peptides in the membrane-bound state. The space-filling solvent-accessibility models emphasize the amphiphilicity by colouring hydrophobic residues in yellow and cationic side-chains in blue. (c) Observed structures and alignment states of the peptides as determined by 19F-NMR...

Another approach to the "greening of catalysts has been the use of rare-earth compounds known as inflates. The term inflate is an abbreviation for the trifluoromethanesulfonate (SO3CF3) cation. Some typical triflates that have been used in research include the lanthanides, scandium, and hafnium. These triflates act as Lewis acids (electron acceptors) and can, therefore, be substituted for stronger mineral acids (such as sulfuric acid) with undesirable environmental... 

Reduction of the hydrocarbon 5,6,11,12-tetraphenyltetracene (rubrene) with a sodium mirror in THF gave a dark green solution from which almost black crystals of the tetrakis-sodium salt 83 could be obtained.1353 Two of the four sodium cations (each doubly solvated by THF) are located (Fig. 53) above and below the central tetracene skeleton and the other two are between pendant phenyl groups. The central sodium ions are 8-coordinate with Na-C 260-263 pm to the phenyl-substituted and 272 pm to the other... 

Cyclic ethers, cyclic acetals, and some vinyl compounds can be polymerized by cationic processes. Photoinitiation of these polymerizations by ultraviolet light are known (12,106). Some extension of direct photolytic sensitization of cationic processes to visible wavelengths is obtained by the use of colored diazonium salts as initiators. For example, Schlesinger (11a) used diazonium salts substituted in the para position with electron withdrawing groups, but sensitivity was limited to the blue to green regions of the spectrum. 

Diphenylmethane and triphenylmethane dyes are monomethine dyes with two or three terminal aryl groups, of which at least one, but preferably two or three, are substituted by a donor group para to the methine carbon atom. The most important donor is the amino group. Important dyes belonging to this class include the well-known malachite green (12) [9] and crystal violet (13) [10], which are some of the oldest synthetic cationic dyes ... 

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