Carbon hydrophobic character

Green coloration, present in many vegetable oils, poses a particular problem in oil extracted from immature or damaged soybeans. Chlorophyll is the compound responsible for this defect. StmcturaHy, chlorophyll is composed of a porphyrin ring system, in which magnesium is the central metal atom, and a phytol side chain which imparts a hydrophobic character to the stmcture. Conventional bleaching clays are not as effective for removal of chlorophylls as for red pigments, and specialized acid-activated adsorbents or carbon are required. 

Figures 6.2 and 6.3 compare the SANS scattering responses, for RH=0.11 and RH=0.87, of the dry carbon, the carbon+TD, carbon+0 0, and carbon + D O+TD. The loss of intensity due to the reduced contrast factor is evident in the region 0.2A

Coal with more than 85% w/w carbon have usually been shown to exhibit a greater degree of hydrophobic character than the lower-rank coals, with the additional note that the water density may be substantially lower than the helium density for the 80 to 84% carbon coals, there is generally little, if any, difference between the helium and water densities. However, the hydrophobicity of coal correlates better with the moisture content than with the carbon content and better with the moisture/carbon molar ratio than with the hydrogen/carbon or oxygen/carbon atomic ratios. Thus, it appears that there is a relationship... 

Silyl groups, which tend to increase lipid solubility, may be used as a substitute for alkyl branching in space-filling groups. Direct substitution of a silicon atom for a carbon atom increases the hydrophobic character of a compound, even without the addition of more alkyl groups. Table III lists the relative partition coefficients of two pairs of carbon and silicon compounds in octanol-water, a system used to approximate the lipid-water system within an organism. As may be seen from the table, the silicon compounds are two to five times more soluble in the octanol phase this effect falls off with an increasing number of carbon atoms in the parent structure (36). 

Molecularly Related Nitrophenols. To define more explicitly the relative influences of molecular structure and hydrophobic character upon rate of adsorption of pesticide materials by porous carbon, a number of pure dinitrophenols molecularly related to DNOSBP and DNOCHP have been studied. The molecular structures of DNOSBP, DNOCHP and the molecularly related dinitrophenols—DNP, DNC, DNT, and DNPCHP —are illustrated in Figure 5. 

A high degree of hydrophobic character is an almost unique characteristic of silicon-rich or pure-silica-type microporous crystals. In contrast to the surface of crystalline or amorphous oxides decorated with coordinatively unsaturated atoms (in activated form), the silicon-rich zeolites offer a well-defined, coordinatively saturated sur ce. Such surfrces, based on the strong covalent character of the silicon-oxygen bond and the absence of hydrophilic centers, display a strong hydrophobic character unmatched by the coordinativeiy unsaturated, imperfect surfaces. Also, hydrophobic zeolite crystals have been reported to suppress the water affinity of transition metal cations contained in the zeolite pores. This property permits the adsorption of reactants such as carbon monoxide or hydrocarbons in the presence of water. 

For most of the samples the molecular size distribution was not measured owing to the samples incomplete solubility, which shows their hydrophobic character. The molecular size distribution was determined ( 32) only for HALR humic acid sample (deposit of Ruppia maritima, Linnaeus) using size exclusion chromatography. The carbon content was measured by DOC and by a UV detector. Two peaks were... 

Unlike membranes where cholesterol is present in an unesterified form, only about 30% of the total serum cholesterol occurs as the free species, whereas the remaining 70% exists as cholesterol esters of long chain fatty acids, such as palmitic [CH3-(CH2)i4-COOH], stearic [CH3-(CH2)i6-COOH)], oleic [CH3-(CH2)7-CH=CH-(CH2)7=C00H)], linoleic [CH3-(CH2-CH=CH)3)=(CH2)7-C00H]. The hydrophobic character of long chain fatty acids is directly proportional to the number of carbon atoms in the chain [15]. Conversely, hydrophobicity in fatty acids containing the same number of carbon atoms decreases with the number of double bonds [15]. 

Activated carbons have hydrophobic smfaces with the properly that nonpolar molecules or organic compotmds with a very poor solubility in water such as benzene or toluene are preferably adsorbed. However, small amormts of oxides or functional groups present in the smface can change the hydrophobic character of the adsorbent surface. The capacity of carbonic adsorbents is evaluated by means of benzene adsorption isotherms. 

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