Phenol mass spectral fragmentation

The reaction products from 2,4-dichlorophenol were tetrachloro-phenoxyphenols and tetrachlorodihydroxybiphenyls (Figure 5), as determined from their mass spectra and those of their methyl ethers. 4,6-Dichloro-2-(2, 4 -dichlorophenoxy)phenol (V) was the major phenoxy-phenol the mass spectral fragmentation pattern of o-hydroxyphenol ethers is quite characteristic since a hydrogen transfer occurs during the fragmentation (Figure 6). A trace of a trichlorophenoxyphenol also was detected and was formed presumably by the unsensitized reductive loss of chlorine, discussed previously. 

The ochotensine-type base (173 X = H2) has been obtained by Stevens rearrangement of the non-phenolic AT-methyltetrahydroprotoberberinium salt (172) with methyl sulphinyl carbanion (Scheme 19). Details have appeared of the benzocyc-lobutenyl route to (173 X = CH2) (c/. Vol. 4). The mass-spectral fragmentation pattern of various fumariline type alkaloids has been studied. ... 

Tandem mass spectrometry or MS/MS is frequently used for structural elucidation of phytochemicals to provide more detailed information about the structure and composition of a molecule. This involves two mass spectral steps and fragmentation of the compound occurs between the steps. The two steps may be separated in space or in time depending on whether two distinct separation elements are used (space) or two different separations occur in the same place over time. As described previously, an IT analyzer can be used to successively fragment a molecule to provide MS" spectra, an example of separation in time. A triple quadrupole mass spectrometer is a form of tandem mass spectrometry in space in which two quadrupoles serve as mass filters while a third, positioned in the middle, allows for collision-induced dissociation. Triple quadrupoles are common in phytochemical analysis, and have been used to characterize phenolic compounds in fruit juices (Abad-Garcia et ah, 2009) and procyanidins and alkaloids in cocoa (Ortega et ah, 2010), among others. 

Mass spectrometric data to identify phenolic acids is getting more prevalent. Carini et al. [96] and Kammerer et al. [98] published valuable data about the determination of several phenolic acids and derivatives by HPLC/MS, in mate and black carrot, respectively. The data about the determination of phenolic compounds in wine was reviewed by Monagas et al. [72]. Positive ion thermospray LC/MS using a discharge electrode to effect solvent-mediated chemical ionization yields [M + H]+ ions and some fragmentation to principal losses of H2O, CO, and CO2, when applied to the analysis of simple phenolic acids [99]. Electrospray LC/MS is a more promising method and used successfully to determine phenolic acids and conjugates. Mass spectral data of several phenolic acids in flow injection analysis particle beam electron impact (FIA-PB-EI) MS is shown in Table 10.10 [100]. 

Lasiodine-A (59) (33), though not a cyclic peptide, exhibits many of the structural features common to that class and could conceivably result from subsequent scission of a cyclic precursor (4). Spectral study identified an isopropylidene, a secondary hydroxyl, a phenolic hydroxyl, and an ester function. Mass spectra fail to reveal the molecular ion but a fragment of mass M-I06 as known from some other peptide alkaloids containing phenylserine as ring bond amino acid (30,31,62). Catalytic hydrogenation generates N-methylvaline and a moiety (83) whose structure was deduced from spectral studies and from hydrolytic degradations. Reduction of the alkaloid with lithiumaluminiumhydride... 

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