Hydrogen-Bonded Complexes with Polar Organic Compounds

Hydrogen-Bonded Complexes with Polar Organic Compounds 

Many types of organic compounds do not have a solubilizing effect on the precipitate. Compounds that are insoluble in water have no effect also, highly hydroxylated compounds such as ethylene glycol or sugar arc inactive. Other compounds tend to coagulate the silica even in the absence of gelatin. 

Temperature has a marked effect on hydrogen-bond formation. Few, if any. of the phenomena here discussed will occur, for example, at 60 C. The complexes are increasingly stable as the temperature is lowered from 30 to 0 or 5 C. 

The relative molar effectiveness of representative compounds of different classes is shown in Table 3.11. 

There appear to be two important factors that increase the affinity between the polar organic molecule and the surface of the silica polymer, multiple bonding and surface activity  

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Metal ions in aqueous solution exist as complexes with water. The solubility of organic compounds in water depends primarily on their polarity and their ability to form hydrogen bonds with water. Organic compounds with a large part of polar components such as acetic acid, dissolve in water without limit. In such cases, the polar part dominates. By contrast, soaps and detergents have a polar end attached to a relatively large nonpolar part of the molecule. They have limited solubility and the molecules tend to coalesce to form micelles. 

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