LXXXVIII.—The influences modifying the specific rotatory power of gallotannic acid

Dimeric (Gemini) Surfactants: Effect of the Spacer Group on the Association Behavior in Aqueous Solution

“…It arises because the equivalent conductivity of a small aggregate of surfactant ions (whether monomeric or dimeric) is larger than the sum of the equivalent conductivities of the ions constituting it (33,39). This effect shows at different values of m for different dimeric surfactants (14,16,37,38) but always at m ≥ 14-16. However, it is already detected at m = 11 for more complex dimeric surfactants derived from arginine where the peptide segment separating the two charged groups may help in stabilizing small premicellar aggregates (39).…”

“…The variation of the log cmc with the alkyl chain carbon number m showed a strong upward curvature or a minimum for m ≥ 16, instead of the usual linear variation. Premicellar aggregation was later reported for other series of dimeric surfactants (14,16,37,38). Electrical conductivity measurements are particularly well suited for obtaining evidence of premicellar aggregation (33,39).…”

Alkanediyl-α,ω-bis(dimethylalkylammonium bromide) Surfactants

“…Many papers have discussed the state of ionic dimeric surfactants in aqueous solution at concentrations below the cmc in an attempt to explain results concerning such systems (4,(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22). Several of these studies involved measurements of surface tension for the determination of the surface area occupied by a dimeric surfactant at the air/water interface and its cmc (4,(11)(12)(13)(14)(15)(16) and of electrical conductivity for cmc determinations (17)(18)(19).…”

Synthesis and Biological Properties of Gemini Quaternary Ammonium Compounds, 5,5'-[2,2'-(.ALPHA.,.OMEGA.-Polymethylnedicarbonyldioxy)diethyl]bis-(3-alkyl-4-methylthiazolium iodide) and 5,5'-[2,2'-(p-Phenylenedicarbonyldioxy)diethyl]bis(3-alkyl-4-methylthiazolium bromide)

“…The gemini QACs possess a unique structure, a greater surface activity and greater antimicrobial potency than conventional mono-QACs. Chemists have studied their physicochemical properties [4][5][6] and greater effective antibacterial potency than the corresponding mono-QACs. [7][8][9] We have also described the syntheses of gemini QACs, which have two cationic pyridiniums, and discussed their antimicrobial activities and characteristics.…”