Chain Length Of Alkylamine Research Articles

Modification of the Interlayer in HTiNbO5 and its Physicochemical Characterization

A layered titanoniobate, in which the interlayer of the metal oxide based on octahedral framework is pillared with silica, has been prepared from HTiNbO5 by employing alkylamines (CnH2n+1NH2, n = 4, 6, 8, 10) and tetraethylorthosilicate as interlayer exchange guests and a pillar precursor, respectively. The incorporated amine had bilayer arrangements in the interlayer space and their ammonium head groups pointed to the host (TiNbO55 −) layers. While the basal spacing of the compounds increased with the chain length of alkylamine. the inclination angle also increased. The intercalated structure facilitated the incorporation of tetraethylorthosilicate into the interlayers, and silica-pillared layered titanoniobate was obtained after calcination. The physicochemical properties of the resultant pillared compounds were characterized on the interlayer microstructure, nitrogen adsorption and UV-VIS absorption spectra.

Aminolysis of naphthyl acetates catalyzed by cyclodextrins

The effects of cyclodextrins (CDs) on the rate of nucleophilic attack on 1- and 2-naphthyl acetates (1-NA and 2-NA) in aqueous solution have been investigated. Analysis of the variation of the pseudo-first-order rate constants with [nucleophile] and [CD] affords rate constants for reaction of the nucleophiles with free ester (kN) and with ester bound to the CD (kcN). The reaction of 1-NA and 2-NA with the trifluoroethoxide anion is slowed down by β-CD as the ratios kcN/kN are 0.11 and 0.30, respectively. For reaction with the anion of 2-mercaptoethanol in the presence of α-CD, β-CD, "hydroxypropyl-β-CD" (hp-β-CD) and γ-CD, the reactivity ratios kcN/kN vary between 0.04 and 2.4, ranging from strong retardation to modest catalysis; the retardations arise with β-CD and hp-β-CD, which bind the esters strongly. By contrast, the attack of primary alkylamines is generally accelerated, and in many cases substantially so. For the aminolysis of 1-NA in the presence of β-CD, values of kcN/kN range from 7 to 460, assuming that free amine reacts with CD-bound ester. Alternatively, if the CD-catalyzed reaction involves free ester reacting with CD-bound amine, with rate constant kNc, the ratios kNc/kN vary from 43 to 140. Either way, there is appreciable catalysis of the aminolysis of 1-NA by β-CD. For the aminolysis of 2-NA, the effects are less dramatic: the ratios kcN/kN range from 0.19 to 17, and values of kNc/kN vary from 17 to 110. The reaction of 1-NA with n-hexylamine is also catalyzed by γ-CD. The variations of kinetic parameters with alkylamine chain length suggest that the CD-catalyzed aminolysis basically takes place by the attack of CD-bound amine on the free ester. However, there must be some stabilizing interactions between the aryl group of the ester and the CD during the reaction, since the transition state stabilization is different for 1-NA and 2-NA, as well for other esters.Key words: aminolysis, catalysis, cyclodextrin, ester cleavage, kinetics.

Development of system suitability tests for ion-interaction chromatography of colorants on reversed-phase packing materials

Ion-interaction reagent (IIR) chromatography has been established as a highly selective and sensitive method for studies on ionic solutes in environmental and food analysis. This technique makes use of a mobile phase containing an ion-interaction reagent (alkylammonium phosphate) which, flowing in isocratic conditions, induces a modification of the stationary phase surface. The formation of an electrical double-layer adsorbed onto the original RP packing material permits the separation of anionic and/or cationic species. As an essential requirement for transferring of IIR methods, it is necessary to devise suitable conditions for validation of the methods. The present work describes the development of system suitability tests (SSTs) based on a group of red dyes as a model system, where the influence of a number of parameters has been examined, including: organic modifier percentage, mobile phase pH, alkylamine chain length, IIR concentration, column temperature, flow-rate, sample composition. Some factors affecting sample stability have also been explored. To extend the results, two yellow dyes were added to the mixture, to provide a group of peaks characterized by critical resolution. Standardized conditions are proposed to assess the suitability of a new column packing material for adequate resolution of the proposed system.

Capillary Wave Propagation on Water Covered with Polyamic Acid Monolayer Films

Externally generated capillary wave propagation has been studied on water covered with poly(amic acid) alkylammonium salts. In addition, fluorescence microscope observation was performed with a poly(amic acid) containing a fluorophore dye. The octadecylammonium salt of this polymer exhibits condensed liquid/gas coexistence films when the pressure is very low (pressure Π≃0), where the liquid phase is highly viscoelastic. Such domain structures were not found in the hexadecylammonium salts of other polymers. However, all films used here can be compressed homogeneously and isotropically at higher pressures, independent of the chain length of alkyl amines. These observations suggest that the mechanical character in the highly condensed state is determined mainly by the flexibility of polymer chains, while the degree of condensation in the dilute state is more influenced by the alkyl amines.