Vincent C. Reinsborough

Raman studies in micellar sodium octyl sulphate solutions

Raman spectra of micelle-forming sodium octyl sulphate have been measured as a function of concentration over the critical micelle concentration. Accurately measured frequency shifts of the C—H stretching region and relative intensities at 1080 and 3125 cm–1 characteristic of gauche isomeric forms can be used as indicators of micelle formation. Quantitative Raman measurements can be used to measure solubilization of organic additives to micellar solutions. Studies of the effects of cations on the halfwidth of the O—SO–3 symmetric stretching vibration indicate a strong interaction with Ca2+, perhaps even complex formation. This blocking effect may account for the decreased catalytic ability of micelles in the presence of Ca2+.

Kinetics of Dye/β-Cyclodextrin Interactions

The rate of association of β-cyclodextrin (β-CD) with each of three similar azo dyes, methyl orange (MO), methyl red (MR) and pyridine-2-p-dimethylaniline (PADA) was determined by the continuous flow method of integrating observation (CFMIO) at pH 8.4. For all three systems, the rate constants were similar and decreased with increasing dye concentration from 107dm3mol-1 S-1 in l mmol dm-3 of β-CD solution to k = 104 dm3mol-1 S-1 in 7 mmol dm-3 β-CD solution. Discrepancies with joule-heating temperature jump results in the literature disappeared when the rate constants were re-determined in 0.5 mol dm-3 NaCl. The chloride ion was identified as the weakly binding species to β-CD that affected the temperature-jump results. Binding constants were obtained conductometrically for the β-CD/M0 and β-C /MR complex species and for β-CD/PADA by a competitive stopped-flow method. The principal inclusion complex with MO is 1:1 but with MR a considerable quantity of the 2:1 β-CD/MR complex is also formed.