Lipophile character

In spite of being ionic many quaternary ammonium salts dissolve m nonpolar media The four alkyl groups attached to nitrogen shield its positive charge and impart lipophilic character to the tetraalkylammonium ion The following two quaternary ammonium salts for example are soluble m solvents of low polarity such as benzene decane and halo genated hydrocarbons... 

The amino group is readily dia2oti2ed in aqueous solution, and this reaction forms a basis for the assay of sulfas. Aldehydes also react to form anils, and the yellow product formed with 4-(dimethylamino)hen2a1dehyde can be used for detection in thiu-layer and paper chromatography. Chromatographic retention values have been deterrnined in a number of thiu layer systems, and have been used as an expression of the lipophilic character of sulfonamides (23). These values have corresponded well with Hansch lipophilic parameters determined in an isobutyl alcohol—water system. 

Unfortunately, there is a significant disadvantage resulting from appHcation of insect-resist agents from dyebaths it is impossible to ensure 100% exhaustion (transfer of pesticide from dyebath to fiber) and as a result, there is inevitably some environmental contamination. The extent of concern with this release of insect-resist agent depends on the spectmm of activity of the agent. If it is a broad-spectmm insecticide, especially one with reasonable persistence and lipophilic character, it is Hable to be reasonably toxic to aquatic insects and invertebrates, especially in certain environmental locations where... 

A formidable array of compounds of diverse structure that are toxic to invertebrates or vertebrates or both have been isolated from plants. They are predominately of lipophilic character. Some examples are given in Figure 1.1. Many of the compounds produced by plants known to be toxic to animals are described in Harborne and Baxter (1993) Harborne, Baxter, and Moss (1996) Frohne and Pfander (2006) D Mello, Duffus, and Duffus (1991) and Keeler and Tu (1983). The development of new pesticides using some of these compounds as models has been reviewed by Copping and Menn (2000), and Copping and Duke (2007). Information about the mode of action of some of them are given in Table 1.1, noting cases where human-made pesticides act in a similar way. 

Hansch C. Qnantitative relationships between lipophilic character and drng metabolism. Drug Metab Rev 1972 1 1-14. 

Hansch C, Clayton JM. Lipophilic character and biological activity of drugs. II. The parabolic case. J Pharm Soc 1973 62 1-21. 

Esterification increases the lipophilic character of the pigments that has been recogiuzed as an important factor for interactions with the peptide chains of proteins. The hydrolysis of this side chain results in chlorophyllides and the concomitant removal of the Mg + ion in pheophorbides. Only a Umited number of natural chlorophylls in plants and photosynthetic organisms has been described and is well... 

The degree of lipophilicity of a pigment molecule can play a major role in its bioaccessibility. Obviously, a compound with a lower lipophilic character will be... 

Microbial 0-methylation to chloroanisoles may occur, and under aerobic conditions these may be terminal metabolites. As a result of their lipophilic character they may be transported into higher biota and hence into the food chain via earthworms (Palm et al. 1991). 

C. Hansch and W.J. Dunn III, Linear relationships between lipophilic character and biological activity of drugs. J. Pharmaceut. Sci., 61 (1972) 1-19. 

According to the colloid scientist Winsor, surfactants are defined as compounds which possess in the same molecule distinct regions of hydrophilic and lipophilic character. For example, in the oleate ion there is an alkyl chain that is basically hydrophobic (lipophilic tail) and a COO" headgroup that is hydrophilic (lipo-phobic). Being amphiphilic in nature, surfactants have the ability to modify the interface between various phases [66]. Their effects on the interface are the result of their ability to orient themselves in accordance with the polarities of the two opposing phases. The polar part can be expected to be oriented towards the more polar (hydrophilic, aqueous) phase, whereas the nonpolar tails should direct towards the nonpolar (lipophilic, oil) phase. 

Therefore, the efficacy of the photoactivity is once again influenced by the hydrophilic/lipophilic character of the compounds.57,58... 

Multipurpose tinting pastes usually contain pigment and hydrophilic solvents, sometimes some amount of water, and suitable wetting agents, which define the equilibrium between hydrophilic and lipophilic character. Conditions to be met in each case depend on the type of paste and on the method by which it is produced and also on the intended use of the coating or paint. 

Hansch C and Dunn WJ (1972) Linear Relationships Between Lipophilic Character and Biological-Activity of Drugs. J Pharm Sci 61 pp 1-19. 

The direct quaternization of chloromethylated polystyrenes by tertiary amines or phosphines represents the easiest way to obtain polymer-supported quaternary onium salt (12,13). A lipophilic character of quaternary cation and a topology allowing sufficient cation-anion separation also play an important role (35,36). A linear spacer chain (of about 10 carbon atoms) between the catalytic site and the polymer backbone substantially increases the reaction rates. The loading of quaternary onium groups also affects catalytic efficiency, the influence being different for directly bonded and spaced groups, e.g. 10 and 11, respectively (37). 

Systematically increasing the size and lipophilic character of the tertiary amino group by replacing the dimethylamino substituent with acyclic and cyclic amines failed to produce much increase in activity, and the weakly basic pyrazole (11) and triazole (12) were both inactive. However, the N-imidazolyl compound (13) was unexpectedly found to be at least 10-times more potent (RVN pA2 7.61) than the parent dimethylamino derivative (10) and became a template for further elaboration. 

Due to its lipophilic character, chloroform accumulates to a greater extent in tissues of high lipid content. As shown by the results presented above, the relative concentrations of chloroform in various tissues decreased as follows adipose tissue > brain > liver > kidney > blood. 

The ocular route is used mainly for the local treatment of eye pathologies. Absorption of drugs administered by conventional eyedrops can result in poor ocular bioavailabilities (2-10%). This is due to the limited area of absorption, the lipophilic character of the corneal epithelium, and a series of elimination factors that reduce the contact time of the medication with the comeal surface, such as drainage of instilled solutions, lacrimation, and tear turnover and tear evaporation [56]. 

The bisindole alkaloids of Catharanthus exhibit ambiphilic behavior in solution, owing, in large part, to their gross lipophilic character combined with the presence of four nitrogen atoms of varying basicity. The upper... 

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