Fragmentation of compounds

Compound 10 was also prepared using acetone-d6 Peak shifts between the mass spectra of compounds 10 and 10a will be used to interpret the fragmentation of compound 10. 

The dendrons were initially incubated with TFA to afford their amine salts, which dissolved in dimethylsulfoxide (DMSO). Then, the solutions were diluted into methanol with 10% triethylamine. The sequential fragmentation of compounds... 

Figure 7. Fragmentation of compounds 4-7 on electron impact. Two m/z values are given under each ion. The first value predominates in the observed mass spectrum and corresponds to the l-I3C- abeled ion. The second value, in parentheses, corresponds to the 6-13C-labeled ion (6,1). (Numbers 1 and 6 within the structures...

Fragmentation of compounds with metal-cyclopentadienyl bonds has been observed to give rise to very abundant CsHsSi ions (e.g., entries 9, 14, and 15). In Eq. (129), they correspond to the base peak... 

A novel preparation of the 1,4-diazepine system (174) has been reported through isomerization of the Schiff base (175).186,187 This same type of diazepine (176) was prepared by the reaction of acetylacetone and meso-l,2-diphenylethylenediamine.188 Spectroscopic studies indicated that it was in the form shown. The NMR spectra of these 2,3-dihydro-l,4-diazepines and their cations have been discussed.187 The Schiff base of benzaldehyde and 1,2,3-triaminocyclopropane also isomerizes to give 174 (R = C6H5, R = C6H6CH=N).186 187,189 The mass spectrometric fragmentation of compounds of the type 176 has been reported.180a... 

Mass spectrometry (MS) this is based on the fragmentation of compounds into smaller units. The resulting positive ions are then separated according to their mass-to-charge ratio (mjz) (Chapter 30). 

Metaphosphonic Acid Anhydrides. In a related process, the fragmentation of compounds 5 (77) and 7 (7) by thermal or photochemical means releases fragments (6 or 8) that are the metaanhydrides of phosphonic acids. The properties of these species are very similar to those of the metaphosphates. 

The specific types of reactions discussed are chemical reactions in which the reactants may be compounds, fragments of compounds, elements, or ions the stoichiometric units are moles and the concentrations of the reactants are given in terms of moles/liter. However, this does not exclude the use of the system by other scientific disciplines. For example, Garfinkel and Sack describe an application of reaction system models to ecological systems. The medium in which the reactions take place may be a pond or a forest and the reactants may be particular plant or animal species. In this case the reactions describe the growth and decay of species in the pond. The concentration of a reactant is more conveniently thought of as the population of a particular plant or animal species. In comparison with chemical reactions, both rate and equilibrium reactions occur in each t q)e of model, but the rate expressions are considerably different. As certain conventions apply to chemistry that may not apply to other areas, the model is usually discussed in terms of chemical reactions. For example, the rate of a chemical reaction is usually proportional to the product of concentrations of reactants on the left hand side of the reaction. 

Fig. 7.13. Correlation of Ge-Cl distances (filled symbols) and Ge-X distances (empty symbols) vs. deviation Az of Ge from Rj plane towards Cl in the ClGeR3X fragment of compounds 20-33 (circles R3=CCl2, X=0 triangles R3=C3, X=N squares R3=C3, X=0). Solid curves, see text...

Very little information is available on the mass spectroscopic behavior of dithienylalkanes, but it is clear that an important fragmentation of compounds of the type (2-C4H3S)2CHX is the loss of X, presumably to produce... 

Taking into account that the sugar fragments of compounds 112, 119, and 123 have acid-labile protective groups, instead of simple vinyl ethers, the (Z)-propenyl ethers were used. Owing to the stereospecificity of the cycloaddition [91,93,94], such a modification should not change the preferred approach of both reactants (Scheme 35) [107]. 

Dibenzylthiobutadienes 59 undergo reductive debenzylation under the action of sodium metal in liquid ammonia at — 70°C with the formation of sodium dithiolate (60) which is instantly oxidized either with air oxygen or with special oxidants (iodine, iron chloride) to 1,2-dithiines 55. l,4-Di(/-butylthio)buta-1,3-dienes (61) afford 1,2-dithiins 55 by treatment with (o-nitrophenyl)sulfenylchloride via disulfide 62. 1,2-Dithiins 55 can be transformed to the corresponding thiophenes 63 [see also (92MI1)]. The formation of 63 is also observed upon the fragmentation of compounds 55 in the mass spectra (principal peak) (96T12677). 

FIGURE 9.7 Fragmentation of compound B and its two isomeric monooxygenated metabolites, B1 and B2. 

Thermal and photochemical fragmentations of compound (179) have been examined. Thermolysis results indicated the intermediacy of biradical (180) but no clear... 

Detailed schemes have been outlined for the fragmentation of compounds (2) and (3) and the l,6-anhydro-j8-pyranose and j3-furanose analogues as well as 2,3-epithio-jS-D-allofuranose, A range of disaccharides specifically labelled with was synthesized for mass spectrometric analysis they were mainly... 

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