| 1. |
- Cabaleiro-Lago, Celia, et al.
(författare)
-
Characterization of alkane diol-CD complexes. Acid denitrosation of N-methyl-N-nitroso-p-toluenesulphonamide as a chemical probe
- 2006
-
Ingår i: JOURNAL OF INCLUSION PHENOMENA AND MACROCYCLIC CHEMISTRY. - Univ Vigo, Dept Quim Fis, Vigo 36200, Spain. Univ Santiago de Compostela, Dept Quim Fis, Santiago De Compostela 15706, Spain. : SPRINGER. - 1388-3127. ; 54:3-4, s. 209-216
-
Tidskriftsartikel (refereegranskat)abstract
- A study was carried out on the acid denitrosation of N-methyl-N-nitroso-p-toluenesulfonamide (MNTS) in mixed systems made up of linear (geminal and terminal) alkyl diols and beta-cyclodextrin (CD). The alkyl diols used allowed us to vary the length of the hydrocarbon chain from 2 to 6 carbon atoms. The observed rate constant, k(obs), decreases in the presence of CD. The inhibition profile decreases as the as the number of carbons in the chain is increased. This behaviour can be interpreted as a consequence of a balance between the complexation processes of MNTS and the alkyl diols by the CD. At a constant CD concentration and increase in the diols concentration decreases the concentration of free cyclodextrin available to complex with MNTS molecules and therefore produces an increases in the observed rate constant. The results were interpreted in terms of two different models; trough the presupposition and non-presupposition of a stoichiometry for the CD-diols complex. Both models agreed quite well and allow us to determine the uncomplexed cyclodextrin concentration in each case as well as the stoichiometry of the complexes. The binding constant for both types of alkane diols increase with increasing the number of carbon in the chain. Besides, the binding constant of the alpha,beta-alkane diols is higher than for the analog alpha,beta-alkane diols. One of the main consequences of this study is that the acid denitrosation of MNTS can be use to obtain the stochiometry of the CD-diol complexes and to monitor the free cyclodextrin concentration.
|
|
| 2. |
- Cabaleiro-Lago, Celia, et al.
(författare)
-
In search of fully uncomplexed cyclodextrin in the presence of micellar aggregates
- 2006
-
Ingår i: Journal of Physical Chemistry B. - Univ Vigo, Fac Quim, Dept Quim Fis, Vigo 36310, Spain. Univ Santiago, Fac Quim, Dept Quim Fis, Santiago 15782, Spain. : AMER CHEMICAL SOC. - 1520-6106 .- 1520-5207. ; 110:32, s. 15831-15838
-
Tidskriftsartikel (refereegranskat)abstract
- The chemical behavior of beta-cyclodextrin/nonionic surfactant mixed systems has been investigated using the basic hydrolysis of N-methyl-N-nitroso-p-toluenesulfonamide as a chemical probe. The experimental results prove that at the cmc, there are significant quantities of uncomplexed beta-CD in equilibrium with the micellar aggregates. In contrast to the expected situation, the percentage of uncomplexed beta-CD in equilibrium with the micellar system increases on increasing the hydrophobicity of the surfactant molecule. This behavior is due to the existence of two simultaneous processes: complexation of surfactant monomers by cyclodextrin and the process of self-assembly to form micellar aggregates. The autoaggregation of surfactant monomers is expected to be more important than the complexation process in this mixed system. Varying the hydrophobicity of the surfactant monomer enabled us to determine that the percentages of uncomplexed cyclodextrin in equilibrium with the micellar system were in the range of 5-95%.
|
|
