Surfactants complexes with biphenyl

In the previous sections, all described complexes were formed between the aromatic compounds and surfactant molecules which have alkyl groups with even-number carbon atoms, such as hexadecyl, tetradecyl, dodecyl and decyl groups. These even-carbon-chain surfactants are utilized widely in vitro and are commercially available. However, there are several odd-carbon-chain fatty acids in vivo, although most fatty acids have even-carbon chains. The former acids are digested in the rumen of ruminants. The odd-carbon-chain surfactants were synthesized from the corresponding odd-carbon-chain fatty acids [56-58]. Two kinds of surfactant molecules with alkyl groups of odd-number carbon atoms, pentadecyl- and tridecyltrimethylammonium bromides (PTAB and TTAB, respectively), were prepared and their complexes with biphenyl were formed. The crystals were obtained from aqueous solutions. 

Complex Formation of Odd-Number Surfactants with Biphenyl [54]... 

Since the occupancy factor of the biphenyl molecule in each site is 0.5, the biphenyl molecule occupies alternate positions along the a-axis. Therefore, there are no short contacts between them along the a-axis. This observation is distinct from the anthracene complex crystal, in which the anthracene molecules adopt a disordered structure along the a-axis, see above. This may suggest that there are fairly strong interatomic interactions between the atoms of the biphenyl and surfactant molecules compared with those of the anthracene complex. 

Complex formation only by grinding a mixture in a mortar was examined for a variety of combinations of the surfactant and aromatic compounds. The CTAB, MTAB, LTAB and DTAB surfactants were selected along with hydrophilic aromatic compounds containing hydroxyl, carboxyl and imino groups, and hydrophobic aromatic compounds such as acridine, anthracene, biphenyl and phenanthrene. Table 4.2 shows the results of the complex formation, in which the letters A, B and C mean that the complex was formed completely, partly and hardly, respectively. (The asterisk indicates that the single crystals have been analysed by X-rays). It is clear that ... 

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