Solvent effects congeners

Fig.8. Effect of tilorone and congeners on the thermal transition temperature (Tm) of calf thymus DNA. Solvent is 0.01 M Tris-HCl pH 7.0 and the concentrations of DNA-P and congeners are 5 x 10-6M, respectively. Curve 1 = DNA 2 = DNA + MEAA-fluorene 3 = DNA + DEAA-fluorene 4 = DNA + DMAA-dibenzothiophene 5 = DNA + DMAA-dibenzofuran and 6 = DNA + DEAE-fluorenone...

All PCB congeners are also lipophilic, as was the corn oil used to dissolve the mixture. The mixture, however, was not completely soluble in corn oil and 5% diethyl ether was used as a solvent to ensure complete solubility and homogeneity. Diethyl ether is a hydrophile with a K(W of 0.89. It is not known what role the diethyl ether played in the mixture effects noted. 

The effect of dissolved organic matter on the solubility of DDT and two PCB congeners is illustrated in Figure 2.8. This study demonstrates that the solubility of the chlorinated hydrocarbon was increased with the amount of soil humic acid added. It must be emphasized that this increase does not result from an effect on the solvent but it is due to the association of the solute with the dissolved humic acid. With these hydrophobic compounds it would appear that the association is due to their partitioning into rather than adsorption onto the humic acid since the two PCB congeners do not compete, that is, the trichlorobiphenyl does not reduce the association of the pentachlorobiphenyl. (The partitioning process is discussed in more detail in the analysis of the sorption in soil.)... 

Squaramides offer yet another variant of the bis-NH proton donor with different geometry compared to thioureas and their congeners. Thus, the quinine-derived squaramide (238b) can catalyse Michael addition of -dicarbonyls to ArCH=CHN02. Here, brine has been found to provide remarkable rate acceleration and a higher level of stereoselectivity (>98% ee) over organic solvents, presumably because of the hydrophobic hydration effect. ... 

Partially water-miscible organic solvents (PMOSs) may act as either cosolvents or cosolutes, and the past research has shown the complexity of their effects. " " It was demonstrated that in order to exert effects on solubility or sorption of HOCs, PMOSs must exist as a component of the solvent mixture in an appreciable amount Munz and Roberts suggested a mole fraction of greater than 0.005 and Rao and coworkers proposed a volume percent of 1% or a concentration above 10 mg/L. Cosolvents with relatively high water solubility are likely to demonstrate observable effects on the solubilities of solutes, up to their solubility limits, in a similar manner to cosolvents of complete miscibility with water. A few experimental examples of the effects of PMOSs include 1-butanol and 1-pentanol acting on PCB congeners " and naphtiialene, and butanone on anthracene and fluoranthene. ... 

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