Chemical Structure and Thermodynamics of Amphiphile Solutions. 1. Solubility of Alkylthiooligooxyethylene Glycols in Water

Article abstract of DOI:10.1021/j100362a016

Solubilities of individual alkylthiooligooxyethylene glycols C_nH_2n+1SCH2CH2(OCH2CH2)_zOH (alkyl: n-C4H9, ..., n-C9H19; and z = 0, ..., 3) in water at 298.15 K have been determined.A quantitative correlation has been found between the standard free energy for transfer from aqueous solution to pure liquid phase, ΔG^o_t, and the structure of the studied sulfides and of oligooxyethylenated alcohols as well by using the appropriate multiple regression equation.It has been found that the thioethylene group, -SCH2CH2-, is hydrophobic.The standard free energy contribution, ΔG^o_t<-SCH2CH2->, is -3.4 kJ mol^-1.The interaction between methylene groups, -CH2-, of the hydrocarbon chain and the -OCH2CH2- groups of the oligooxyethylene chain is statistically significant and has an influence on the total value of ΔG^o_t.Furthermore, the ΔG^o_t<-OCH2CH2-> and ΔG^o_t<-CH2-> are not constant.For the sulfides studied, ΔG^o_t<-OCH2CH2-> increases linearly with hydrocarbon chain length.For example, ΔG^o_t<-OCH2CH2-> for the series of butyl and nonyl derivatives is +0.24 and +0.81 kJ mol^-1, respectively.The ΔG^o_t<-CH2-> for the series of alkyl-2-hydroxyethyl sulfides (z=0) and alkylthiotetraoxyethylene glycol (z=3) is -3.43 and -3.10 kJ mol^-1, and the ΔG^o_t<-OCH2CH2-> and ΔG^o_t<-CH2-> for the group of oxyethylenated alcohols are +0.53 and -3.13 kJ mol^-1, respectively.