Mass spectroscopy, structural

A tertiary base isolated from Thalictrum strictum was assigned a pavine structure based on the spectral data (27). Three methoxyl and one methylenedioxy functions were detected with the aid of mass spectroscopy. Structure 3 was proposed as the most probable representation for this new pavine alkaloid, which indeed is the first example of a pentasubstituted pavine base. However, when the reported aromatic proton chemical shifts (8 6.23, 6.36, and 6.54) were evaluated in the light of empirical rules about the H-NMR absorptions of pavine bases (Section V,B), and it seemed possible that the two upfield absorptions belong to H-4 and H-10 rather than to H-1 and H-10. Therefore, alternative structure 4 cannot presently be completely excluded from consideration. 

Fabbri, D., Chiavari, G., and GaUetti, G. C., Characterization of soil humin by pyrolysisf/methyla-tion)-gas chromatography-mass spectroscopy structural relationships with humic acid, J. Anal. Appl. Pyrolysis, 37, 161-172, 1996. 

The preparation and spectroscopic properties (infrared, ultraviolet, NMR) of iV-alkoxycarbonyl-N -(2-thiazolyl)thioureas (268) have been studied by the Nagano group (78, 264). These compounds react with bromine in acetic acid or chloroform to give 2--alkoxycarbonylimino-thiazolo[3,2-h]thiadiazolines (Scheme 162), whose structures were established by mass spectroscopy, infrared, NMR, and reactivity patterns (481). 

Nitrogen-containing fulvalenes have not been systematically studied by mass spectroscopy. Only isolated data for several examples of compounds have been reported. Most of the data consist of electron impact (El) mass spectra recorded for analytical purposes. Only a minor fraction dealt with the characterization of ion structures or focused on the effects of substituents, the ring size of fulvalenes, or the number and arrangement of nitrogen atoms and the fragmentation pathways. 

Advantage was taken of these solubility differences in refining mixtures of the chlorinated dibenzodioxins. Digestion with boiling chloroform was effective in removing trichlorodibenzodioxin while recrystallization from anisole reduced the penta-substituted isomer content. In a typical purification (Table II) these two procedures were alternated through four cycles. The assays were made by mass spectroscopy using the batch injection method to introduce the sample into the spectrometer. X-ray studies 14) confirmed the structure. 

Peaks are analyzed separately by their retention times, absorption, and fluorescence properties. RCCs show absorbance maxima near A.500 and 316 nm. For FCCs, UV-Vis specna show two prominent bands near 361 and 320 mn and a luminescence maximum at 436 mn and NCCs show UV-Vis spectra with absorbance maxima near 320 and 210 nm. Nevertheless, as none of these approaches is suitable for elucidating structures, it is necessary to apply additional MS and NMR analyses to fully characterize snuctural features. Electron spray ionization (ESI) and high-resolution EAB mass spectroscopy have been applied to elucidate the molecular formulae of colorless compounds. ... 

The structure of the second edition follows that of the first edition, with novel applications contained in sections attached to the individual chapters. The present chapter covers mass spectroscopy, with additional applications being found in the individual chapters, as well as advances in common detectors, unusual modes of chromatography, and general theoretical advances. 

Structural characterization was based on solubility, thermal and elemental analyses, and infrared and mass spectroscopies. Charac-... 

In comparison to humantenine (15), the structure of which has been confirmed by X-ray diffraction analysis, structure 16 can be assigned to humantenirine with reasonable confidence. The proposed structure is supported by the fragmentation pattern (high-resolution mass spectroscopy and... 

If suitable standards are unavailable (for example, if the FBA has not been encountered previously) the active agent must first be isolated and purified. The pure compound can be characterised by the usual techniques, including elemental analysis and infrared, n.m.r. and mass spectroscopy. Final proof of structure demands synthesis of the FBA indicated by the analytical data. Once again, difficulties may be encountered with compounds of the DAST... 

Hufford et al [57] used proton and 13C NMR spectrometric data to establish the novel sulfur-containing microbial metabolite of primaquine. Microbial metabolic studies of primaquine using Streptomyces roseochromogenus produced an A-acety-lated metabolite and a methylene-linked dimeric product, both of which have been previously reported, and a novel sulfur-containing microbial metabolite. The structure of the metabolite as an S-linked dimer was proposed on the basis of spectral and chemical data. The molecular formula C34H44N604S was established from field-desorption mass spectroscopy and analytical data. The 1H- and 13C NMR spectra data established that the novel metabolite was a symmetrical substituted dimer of primaquine A-acetate with a sulfur atom linking the two units at carbon 5. The metabolite is a mixture of stereoisomers, which can equilibrate in solution. This observation was confirmed by microbial synthesis of the metabolite from optically active primaquine. 

Neutral and charged gold carbonyl species have also been observed on gold field emitter tips upon interaction with CO gas at room temperature in the presence of high electrostatic fields. The adsorbed complexes and the desorption pathways were identified using time-of-flight mass spectroscopy. [(CO)Au] species are more abundant than [Au(CO)2] species. The product distribution was rationalized by DF calculations of the electronic structure of the complexes.291... 

Although the structure of MAO was analyzed by different methods, such as IR and NMR spectroscopy, mass spectroscopy and lots more, the exact composition and structure of MAO are still not entirely clear or well-understood [27, 28], It is assumed that the structures of MAO include one-dimensional linear chains, cyclic rings that contain triscoordinated A1 centers, and three-dimensional clusters with tetracoordinated aluminum [24] (Fig. 8). 

---