Determination of the enantiomeric composition of guest molecules by chemometric analysis of the UV-visible spectra of cyclodextrin guest-host complexes

Multivariate statistical techniques were applied to the UV spectra of a series of solutions at pH 12 containing a fixed concentration (30 mM) of beta-cyclodextrin (beta-CD) and a fixed concentration (15 mM) of 2-phenylglycine (phi-Gly) with various known enantiomeric compositions. Multivariate correlation of the spectral data for the solutions containing the phi-Gly/beta-CD guest-host complexes with the known enantiomeric composition of the phi-Gly samples was accomplished by partial-least-squares regression. When the multivariate model was used to predict the enantiomeric purity of a test set of samples over the mol fraction range of 0.5-0.9 R-phi-Gly, the average magnitude of the relative errors in the mol fraction determination of enantiomeric composition was 3%. A plot of the enantiomeric composition predicted by the model versus the known enantiomeric composition of the calibration set gave a straight line with a correlation coefficient of 0.955, a slope of 1.05, and an offset of 5.61 x 10-4.     

A sesquiterpene glucoside from cultivated cells of Scorzonera hispanica

A sesquiterpene glucoside has been isolated from a tissue culture ofScorzonera hispanica, and its structure has been established by mass spectrometry and two-dimensional NMR as 6,9-dihydroxy-4,10,14,15-tetradehydroguaian-6,12-olide 9-O--D-glucopyranoside.Irkursk Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 640–645, November–December, 1992.     

Enthalpies of mixing of charge unsymmetrical binary fused salt systems: ZnX2?AX (A = Li,Cs, Ag; X = Cl,Br)

The enthalpies of mixing (ΔH^M) of the following binary fused-salt mixtures have been determined calorimetrically: ZnCl₂? CsCl, ZnCl₂? LiCl, ZnCl₂? AgCl, ZnBr₂? CsBr, ZnBr₂? LiBr at 665°C; ZnCl₂? CsCl, ZnCl₂? AgCl, and ZnCl₂? ZnBr₂ at 495°C. The results are discussed with respect to the following points: (1) Comparison with the transition metal chloride-alkali chloride systems, (2) “complexing” in the mixture. (3) effect of the network-like structure of pure ZnX₂, and (4) effect of temperature.     

Mass spectrometry of kaurene derivatives—I. The mass spectra of some (−)-kauran-16-ols

The mass spectra of nine compounds belonging to the group of (?)-kauran-16-ols are reported. These compounds differ either by stereochemistry at C₁₆ (I, II) or by the nature of the substituent at C₄ (III to VIII). In all cases the most characteristic ions correspond to a process in which ring D is split off and lost as a C₃H₆O fragment. The nature of the substituent R₁ at C₄ can be deduced from such typical ions as [M ? R₁]+ or [M ? R₁ ? H₂O]+. Kauranols epimeric at C₁₆ show little difference in their mass spectra; the assignment of configuration at this centre may be reliable only when the spectra of both epimers are compared.     

The bromination of 2-amino- and 2-acetylamino-4-(2-furyl)-thiazoles

The bromination of 2-amino-and 2-acetylamino-4-(2-furyl)thiazoles has been studied, and it has been shown that bromination takes place first in the furan ring and then, with an excess of bromine, also in the thiazole ring in position 5.     

Viscous flow of aqueous solutions of copper sulfate in the temperature range 20–50°C

Apparent molar volume, enthalpy of activation, and Gibbs energy of viscous flow of aqueous copper sulfate solutions were calculated from experimental data. The concentration dependences of the above parameters were analyzed from the standpoint of structural transformations. Original Russian Text V.N. Tseluikin, N.D. Solov’eva, O.G. Nevernaya, 2007, published in Zhurnal Prikladnoi Khimii, 2007, Vol. 80, No. 10, pp. 1747–1749.     

Comparison of combustion sources for sulfur chemiluminescence detection

Three different types of SCD combustion source have been evaluated for use in the chromatographic analysis of atmospheric sulfur compounds. The conventional FID source and the newer inverted burner source were found to be less sensitive and less stable than the flameless design. Overall, the flameless source was superior for use with HRGC-SCD.     

Superoxide-mediated dehydrohalogenation reactions of the pyrethroid permethrin and other chlorinated pesticides

Superoxide generated in DMF readily converts the dihalovinyl group of permethrin and related compounds to a haloethynyl moiety and yields major products from elimination reactions of DDT, $\text{cis}$-chlordane, and 1,2-dibromo-3-chloropropane (DBCP).     

Destruction of carbonyl and hydroperoxide groups in oxidised polypropylene: Effect on photo-oxidation

The effect of destroying carbonyl and hydroperoxide groups in oxidised polypropylene on the subsequent rate of photo-oxidation has been examined using infra-red spectroscopy. The results show that carbonyl groups dominate the rate of photo-oxidation in severely oxidised polymer. In mildly oxidised polymer hydroperoxide groups control the rate, but to a much smaller extent. Destruction of the photo-active carbonyl and hydroperoxide groups in the unoxidised and oxidised polymers by prior photolysis in an inert atmosphere gave rise to some interesting and complex effects on subsequent photo-oxidation. The results indicate that although carbonyl and hydroperoxide groups may control the rates of photo-oxidation of thermally oxidised/processed polymer, their importance as primary photo-initiators is highly questionable. Oxygen-polymer charge transfer complexes appear to be the more likely photo-initiators.