82-07-5Relevant articles and documents
High-Fidelity Dimerization of Xanthenyl Radicals and Dynamic Qualities of a Congested Ethane: Diethyl Dixanthenyl-9,9′-Dicarboxylate
Dubrawski, Zachary,Gelfand, Benjamin S.,Hogan, David T.,Sutherland, Todd C.
supporting information, (2021/12/23)
Exploration of the sterically-congested ethane diethyl dixanthenyl-9,9′-dicarboxylate has revealed the dynamic behavior arising from its congested C?C bond. Interlocking ‘geared’ substituents and favorable dispersion interactions around this bond result in a conformational preference for partially cofacial xanthene moieties both in solid state and as dilute solutions. The weak, centrally located C?C bond is 1.628 ? long and permits selective thermolysis to yield two carbon-centered ethyl xanthenyl-9-carboxylate radicals, which dimerize with high fidelity into the original sterically-congested ethane. Recombination of the radicals into this symmetrical head-to-head dimer is highly reproducible – by observing the equilibrium, the bond dissociation enthalpy was calculated to be 20.4 kcal ? mol?1. The substituents around the central carbon provide insufficient stabilization against oxygen, which consumes the radicals and unbalances the dimer-radical equilibrium.
Synthetic method of xanthene-9-formic acid
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Paragraph 0035; 0042; 0043; 0044; 0051; 0052, (2017/12/09)
The invention discloses a synthetic method of xanthene-9-formic acid, which belongs to the field of chemical synthesis. The method comprises the following steps: xanthone is taken as a raw material, then is reduced to xanthydrol under alkaline condition by zinc dust, then the xanthydrol is subjected to a halogenated reaction to obtain the halogenated xanthene, then under effect of a catalyst, a cyanidation reaction is generated to obtain 9-cyan xanthene, through alkali hydrolysis, organic impurity is removed through extraction of an organic solvent, a xanthene-9-formate aqueous solution is obtained, and a xanthene-9-formic acid product is obtained through a neutralization reaction. The method has the advantages of simple operation and safe technology, the xanthene-9-formic acid with high purity is obtained without refining, and the method is easy and effective for industrial production.
A stability-indicating proton nuclear magnetic resonance spectroscopic method for the analysis of propantheline bromide in pharmaceutical samples
Hanna,Lau-Cam
, p. 700 - 703 (2007/10/03)
A rapid, specific and accurate proton nuclear magnetic resonance (1H NMR) spectroscopic method was developed for the simultaneous quantitative analysis of propantheline bromide and its degradation product, xanthanoic acid, in bulk materials and tablets. 1,3,5-Trinitrobenzene served as an internal standard and deuterochloroform was used as the solvent for the analytical samples. The quantities of propantheline bromide and xanthanoic acid were calculated on the basis of the integrals for signals of the methine proton of propantheline at 5.09 ppm, the methine proton of xanthanoic acid at 4.99 ppm, and the aromatic protons of the internal standard at 9.39 ppm. The accuracy of the method was established through the analysis of synthetic mixtures containing the parent compound, its degradation product and the internal standard. An excellent agreement was verified between the assay results and the quantities of the various compounds in the mixtures. The mean ± SD recovery values for propantheline bromide and xanthanoic acid from a set of 10 synthetic mixtures were 99.6 ± 0.8% and 98.9 ± 1.8%, respectively. The assay of 10 lots of commercial propantheline bromide tablets by 1H NMR spectroscopy indicated drug and degradate contents in the ranges 97.1-99.8% and 0.1-0.9%, respectively. In addition, the proposed analytical method was found suitable for detecting the formation of xanthanoic acid from propantheline bromide in aqueous media in concentrations below 0.1% of that of the parent compound.
