Hydrophobicity functional group composition

There are major differences in the chemical compositions of DOM isolated by XAD resins and ultrafiltration (Table I). In rivers and in the ocean, humic substances (XAD isolation) are depleted in N relative to UDOM. The C/N ratios of UDOM are more representative of bulk DOM than those of humic substances. Most of the functional groups identified by NMR are found in more than one class of compounds, so in most cases specific functional groups are not assigned to a particular group of biochemicals. However, in some circumstances it is possible to estimate the fraction of carbon associated with a biochemical class, such as carbohydrates. Carbohydrates are the most abundant polyalcohols in nature, and the ratio (4-5 1) of areas associated with NMR peaks at specific chemical shifts [e.g., 72 ppm (C—O) -102 ppm (O—C—O)] indicates that carbohydrates are their primary source (see Table I for references). In general, humic substances are depleted in carbohydrates (C—O and O—C—O) and enriched in aromatic and unsaturated C (C=C) relative to UDOM (Table I). As mentioned earlier, humic substances are relatively hydrophobic components of DOM, and it is consistent that they are depleted in N and carbohydrates and enriched in aromatic components. The UDOM fraction includes more hydrophilic components that are relatively enriched in N and carbohydrates. Humic substances from the ocean are enriched in aliphatic C (C—C) relative to UDOM, and this could reflect the more hydrophobic nature of the humic substances. 

Similarly, the partitioning of nitroimidazoles into octanol-water, log Poet and into four liposome preparations with different lipid composition, log KM, was determined and regression equations were derived to explain the observed variation in the pharmacokinetic parameters of these drugs [85]. The log fCM ranged from 1.5 to 0.5 and was at least two- to threefold greater than log Poct (Table 4.24). In addition, the hydrophobic substituent constants of functional groups in various partitioning systems... 

Steroids are hydrophobic molecules and sparingly soluble with only one hydroxyl functional group. Normally steroids are found concentrated in the sediment phase via partitioning onto organic matter on sediments (25). Their concentration in the foam and humic-acid fraction is indicative of the hydrophobic nature of these fractions. The increasing compositional complexity from stream, to foam, to foam-extract samples is also consistent with other characterization trends of increasing compositional complexity and hydrophobicity. 

Even simple polymers like polyethylene or polypropylene can form composites with carbon nanotubes. The embedding, however, is limited to noncovalent interaction due to the complete lack of functional groups. Yet on the other hand, the hydrophobic nanotube surface hardly poses any problems in a wetting by the nonpolar polymer chains or in the formation of noncovalently bound composites. 

Titanium silicalite (TS-1) is a porous crystalline titanium silicalite with the MFI structure, analogous to ZSM-5 [1], Catalytic centers are isolated Ti sites in a silica framework [4]. Unlike Ti02/Si02 with a similar elemental composition but an amorphous structure, TS-1 is an effective catalyst for the selective oxidation of different functional groups with dilute aqueous hydrogen peroxide [2]. The structural properties of lattice Ti sites, the hydrophobicity, and the size of the tridimensional channel system (ca 0.55 nm) are thought to be critical factors in determining the unusual catalytic properties of TS-1. 

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