The solution properties of various double-chained anionic surfactants [disodium 5, 12-bis (2-alkyloxymethyl) -4, 7, 10, 13-tetraoxa-1, 16-hexadecanedisulfonate ; 2CnElS3, n=8, 10, 12, 14] with two anionic groups, differing in alkyl chain lengths, were examined by surface tension, micellar diameter, aggregation number and pNa measurements. Critical micelle concentration (cmc) and minimum surface tension at cmc (γcmc) decreased with an increase in alkyl chain length. At the same alkyl chain length, these parameters were less than those of anionic surfactants with single chains and single ionic groups. Micellar diameter (HD), aggregation number (N), occupied area of the hydrophilic group on the micellar surfaces (A) all showed maximum values at n=10. The degree of ionic dissociation of micelles (α) decreased with increasing alkyl chain lengths. Molecular packing on the micellar surfaces was found to depend on the steric structure of the bridge part in the surfactant molecule.
The oxidative stability of unsaturated lipids generally decreases with increase in unsaturation. Highly unsaturated fatty acids such as docosahexaenoic acid (22 6 n-3, DHA) and icosapentaenoic acid (20 5 n-3, EPA) are thus more easily oxidized in air, with consequent decrease in food quality. Few reports on the autoxidative behavior of fatty acids in different molecular forms have appeared to date. The autoxidative behavior of fatty acids (FA), fatty acid methylesters (FAME), triacylglycerols (TG) and phospholipids (PL), all possessing essentially the same fatty acid compositions, was thus examined in this study at 30°C in the dark and the results were compared. The study was made with and then without antioxidant tocopherols (Toc). PL was the most oxidatively stable, followed by TG>FAME>FA, with or without Toc under the autoxidation conditions used. PL hydroperoxide decomposed into carbonyl compounds more quickly than any other lipid. Autoxidative behavior of complex lipid such as PL was different from simple lipids like FA, FAME and TG.
The rheological behaviour of poly (oxyethylene) (10) hydrogenated castor oil dispersions was investigated by oscillation rheometry at 25°C as a function of dispersion concentration and frequency. HCO-10 dispersions were characterized in terms of viscoelastic parameters such as complex viscosity (η*), storage modulus (G') and loss modulus (G″). Based on the results, the following conclusions were drawn. The complex viscosity of HCO-10 dispersions is maximum around 70 wt%. Below this value, storage modulus is greater than that of loss modulus having a gel-like character. Above 70 wt%, loss modulus is greater than that of storage modulus, indicating possibly a liquid-like character. In addition, the viscoelastic parameters were compared with the results of aN' and S33 by ESR spin labelling, T1 relaxation time by NMR and long spacing by small angle X-ray diffraction. It became clear that immobilization of free water in the bilayer of HCO-10 vesicles is indispensable to the gel-formation of HCO-10 dispersions.
Lipase-catalyzed transesterification between tributyrylglycerol (tributyrin) (1) and 2-octanol (2) has been studied in neat at 30°C. The kinetic resolution data fit the reported theoretical equations for the equilibrium reaction. The competitive reactions of the enantiomers in (2) with theacyl-enzyme intermediate which was formed the reaction of the free enzyme and (1) was experimentally proved by an accordance of the enantiomeric excess against the extent of conversion plots for racemic and optically active (2). A reversibility of the transesterification was also shownby a decrease in enantiomeric excess of the product and the unreacted starting material duringthe reaction.
Five new amphiphiles each containing two azobenzene units in a molecule were synthesized through four reaction steps. The first step was azo-coupling reactions with aniline derivatives and phenol. The second step was Williamson etherification reaction between sodium salts of phenols containing an azobenzene unit with ω-halogenated alcohols, such as 2-bromoethanol or 3-chloro-l-propanol. The third step was diesterification reactions between alcohols having an azobenzene unit and maleic anhydride, the diester of maleic acid containing two azobenzene units in a molecule was obtained. The fourth step was addition reaction of sodium hydrogensulfite with diesters. The products were characterized by 1H-NMR, IR, and Mass spectra.
A pseudo-first-order reaction constants (kobs) of dyes having a single hydroxyl group inthe molecule (Orange I, Orange II) by various bleaching agents were measured as a function ofpH. Used bleaching agents were hydrogen peroxide, peracetic acid, potassium permonosulfate, and sodium hypochlorite. The kobs of each dye showed maximum at intermediate pH betweenan acid dissociation constant of bleaching agent (pKa) and an acid dissociation constant of dye (pKd). Distribution curves of kobs on pH showed symmetrical narrow distribution when the value of pKd was close to pKa, and symmetrical broad distribution when the value of pKd was far apart from pKa. These results were analyzed with reaction kinetics by assumming the ionic reaction among protonated and deprotonated form of the bleaching agents and the dyes. It wasproved that the distribution curves of kobs on pH follow the following equation. kobs= [A] t/ (1+ [H+] /Ka) (1+Kd/ [H+]) where [A] t is the total bleaching agent concentration, k1 is a second-order reaction constant byassuming the reaction between protonated dye ; [DyeH] and deprotonated bleaching agents ; [A-]. The calculated values obtained by above equation were in good agreement with the observed values. Therefore, it was concluded that the decoloration mechanism of the dyes by bleaching agents conforms to the ionic reaction among protonated and deprotonated forms of the bleaching agents and the dyes. We have named this decoloration mechanism as “the mutual ionic reaction mechanism”.
A pseudo-first-order reaction constants (kobs) of dyes that having hydroxy groups in the molecule (Acid Orange 6, Mordant Black 17, Alizarin Red S) by various bleaching agents were measured as a function of pH. Used bleaching agents were hydrogen peroxide, peracetic acid, potassium permonosulfate, and sodium hypochlorite. The kobs of each dye showed maximum at intermediate pH between an acid dissociation constant of bleaching agent (pKa) and one of the acid dissociation constants of dye (pKd1 or pKd2). Distribution curves of kobs on pH showed unsymmetrical distribution, because kobs was affected by both acid dissociation constants (pKd1and pKd2) of dye. These results were analized with reaction kinetics by assumming the ionic reaction among protonated and deprotonated form of the bleaching agents and the dyes. It was proved that the distribution curves of kobs on pH follow the following equation. kobs= [A] t/1+ [H+] /Ka· (k1a/1+Kd1/ [H+] Kd1Kd2/ [H+] 2+k1b/1+Kd2/ [H+] + [H+] /Kd1) where [A] t is the total bleaching agent concentration, k1a and k1b are second-order reaction con-stant by assuming the reaction between protonated dye ; [DyeH2] and deprotonated bleaching agent ; [A-], and monodeprotonated dye ; [DyeH-] and deprotonated bleaching agent ; [A-]. The calculated values obtained by above equation were in good agreement with the observed values. This result demonstrated the aditivity of the reaction rate on the decoloration in each case. Therefore, it was concluded that the decoloration mechanism of the dyes by bleaching agents conforms to proceed according to the ionic reaction, and each deprotonated form of dye participate in the decoloration reaction.