Compound fragmentation

The fragment ions are characteristic of any given substance in that the way a compound fragments can be regarded as a fingerprint. For the fragment ions to be useful, it is necessary to know how they relate to each other. In other words, it is necessary to understand which fragment should be connected to which others in the overall chemical structure. 

Fig. ].5 Schematic diagram to show the process involved in crystallographic screening of compound fragment cocktails.

In Fig. 4b fragment ions can be observed, which correspond to 16 Da upwards relative to Pr271 and 32 Da to the parent compound fragments. These data suggest that a double hydroxylation of 4-MBC occurred. The two hydroxyl groups were attached, as in the previous case, in the aromatic moiety of the compound. 

The correct analysis of the homologous ion series has certain limitations. Low abundances of peaks in some series require the attention and experience of a researcher. Usually alkane series are dominated in the mass spectra of the most various compounds. Fragmentation initiated by one functional group may completely suppress or notably camouflage other reactions of polyfunctional substances. In the latter case it is useful to consider IR-spectroscopy data in mass spectral interpretation. 

Because MS identifies components on the basis of their atomic or molecular mass and, in the case of organic compounds, fragmentation pattern, it is a particularly useful and powerful detector. The molecular mass, which is commonly referred to as the molecular weight, is a particularly useful piece of information when trying to identify a compound. For elements, atomic mass determination can also determine the isotope present, which in turn can be used to identify the source and movement of an element through the environment. 

Low PSA increases BBB permeability of compounds. Fragment-based TPSA methodology is also fast and easy to compute for large number of compounds. 

In this template, the lead compound fragment and the two pharmacophoric groups are separated by wildcard designations that denote where chemical variability can occur. 

Hydrazide 1 was designed as the CA anchor fragment and hence necessitated dual functionality an Ar-SO NH moiety for reliable CA affinity and a hydrazide moiety to take part in hydrazone exchange. Hydrazide 2 lacked the sulfonamide moiety of 1, but was still able to participate in hydrazone exchange and thus functioned as a control compound. Fragments A-E, the exchange partners for 1 and 2, were selected to introduce an array of tails onto 1 to enable exploration of periphery recognition interactions with CA. 

Fragmentation pathways of protonated and deprotonated molecules of C-glycosidic flavonoids obtained with CID tandem MS techniques have enabled important structural information to be obtained about different substitution patterns of sugars in this class of compounds.Fragment ions formed by the loss of water were more pronounced for... 

Vainiotalo and collaborators585 measured the electron impact spectra of several either di-exo- or di-mfo-norbornane/ene-fused 2-lV-phenyl iminoperhydro-l,3-oxazines. Whereas the stereoisomeric unsaturated compounds cannot be distinguished on the basis of their electron impact spectra, the spectra of the stereoisomeric saturated compounds are sufficiently different to allow differentiation of the stereoisomers. The N-substituents were either H or Me. The difference is due to the fact that the unsaturated compounds fragment mainly by two RDA reactions with first a loss of cyclopentadiene and then yielding... 

Another fundamental reaction of >C=0 involves its reactivity as a base. In the Brpnsted sense, >C=0 - may react with a proton donor to produce a neutral ketyl radical (>C(.)OH, Figure 2, reaction 2). This is an important process when the reduction of a carbonyl compound is carried out under acidic conditions or in a protic media (e.g. elec-trochemically, with less reactive reducing reagents such as Mg or Zn, or when >C=0"-is produced via PIET and R3N"+ has available a-protons). The follow-up chemistry of >C(.)OH is that of a neutral free radical (dimerization to form pinacols, addition to unsaturated compounds, fragmentations/ring-openings, etc.), and thus beyond the scope of this chapter. 

It is known that 2,3,4-tri-/-butylazete 627 is a remarkable stable, strained, kinetically stabilized heterocyclic compound, which can be distilled (Kugelrohr, bp 60 °C, 0.05 mbar) and has a melting point of 37 °C <1996CHEC-II(1B)507>. The reddish-brown needles are stable for several days at 100 °C, while the compound fragmented at 700 °C (10 6mbar) into di-/-butylacetylene and /-butylcyanide. 

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