Hydrophobic groups alkylbenzenes

As esters of sulfuric acid, the hydrophilic group of alcohol sulfates and alcohol ether sulfates is the sulfate ion, which is linked to the hydrophobic tail through a C-O-S bond. This bond gives the molecule a relative instability as this linkage is prone to hydrolysis in acidic media. This establishes a basic difference from other key anionic surfactants such as alkyl and alkylbenzene-sulfonates, which have a C-S bond, completely stable in all normal conditions of use. The chemical structure of these sulfate molecules partially limits their conditions of use and their application areas but nevertheless they are found undoubtedly in the widest range of application types among anionic surfactants. 

Recent chromatographic data indicate that the interactions between the hydrophobic surface of a molded poly(styrene-co-divinylbenzene) monolith and solutes such as alkylbenzenes do not differ from those observed with beads under similar chromatographic conditions [67]. The average retention increase, which reflects the contribution of one methylene group to the overall retention of a particular solute, has a value of 1.42. This value is close to that published in the literature for typical polystyrene-based beads [115]. However, the efficiency of the monolithic polymer column is only about 13,000 plates/m for the isocratic separation of three alkylbenzenes. This value is much lower than the efficiencies of typical columns packed with small beads. 

Examples of common hydrophobes include alkylphenol, fatty alcohol, paraffin, olefins, and alkylbenzene. Examples of common hydrophiles include ethylene oxide (EO), sulfates, sulfonates, phosphates, and carboxylic acid groups. Depending on the charged nature of the head group, surfactants are classified as ... 

A hydrophobic tail may include such structures as straight-or branched-chain alkyl groups, long-chain alkylbenzenes, alkylnaphthalenes, perfluori-nated alkyl groups, polysiloxane groups, and others. 

Hydrophobicity or hydrophobic selectivity 0-CH2 Retention factor between pentylbenzene and butylbenzene, = kp /k. This is a measure of the surface coverage of the phase as the selectivity between alkylbenzenes differentiated by one methylene group is dependent on the ligand density. 

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