MS fragmentation pattern

The mass spectrum of (/i/.)-penicillamine was obtained utilizing a Shimadzu PQ 0-5000 mass spectrometer. The detailed mass fragmentation pattern is shown in Fig. 7, where a base peak was observed at mlz 75. The proposed mass fragmentation pattern of (/i/.)-penicillamine is summarized in Table 5. It is worth mentioning that the drug did not show a molecular ion peak. A proposed scheme of the MS fragmentation pattern of (z>z.)-penicillamine is shown in Fig. 8. 

Fig. 2.6.14. MS-MS fragmentation patterns of some CAEC (NI mode) (a) CA9PE2C, (b) CA5PE2C, and (c) CA5PE1C. The exact branching of the alkyl chain is unknown the alkyl isomer structures shown are chosen arbitrarily. Reprinted with permission from Ref. [33] 2001 American Chemical Society.

Nakai 124-126). UV and IR spectra of 78 and 81-83 are characteristic of lupinine alkaloids of the cytisine series containing an a-pyridine ring. MS fragmentation patterns are similar to those of cytisine alkaloids. The structures of these alkaloids were confirmed by synthesis from cytisine by reaction with HCOOH (81), (CHjCO) (78), C2H5Br (82), or CH2=CH—COCH3 (83). 

Figure 5-1 shows the GC of fraction 4. It shows alkanes ranging from to C-Q. It is quite possible that the fraction may contain hlgher alkanes which are not detected due to the GC-oven temperature limit. The peaks are identified from the MS fragmentation pattern. Fraction 5 is collected after a 0.5 minute... 

The metabolism of ticlopidine, 45, has been investigated by mass spectral analysis. The principal metabolic pathways can be proposed based on supporting mass spectrometry (MS) fragmentation patterns. Chlorotropylium ion 46 (mlz= 125) is the base peak in the product ion mass spectrum of ticlopidine <2004MI49>. 

The MS fragmentation patterns have been investigated for the most important types of substitution of TPs. The parent compound and its methyl derivatives primarily lose either HCN (or CH3CN, resp.) or N2 [68DIS(B)1303 77HC(30)179],... 

The MS fragmentation patterns of dithio-/J-diketonato complexes differ from those of both /J-diketonato and monothio-/J-diketonato complexes. The mass spectra of bivalent dithioacetyl-acetonato complexes are characterized by a molecular ion peak M and a much stronger peak for L+ due to the formation of the 3,5-dimethyl-l,2-dithiolium ion another peak at tn/e 96 is due to the loss of HS from the dithiolium cation. The mass spectra of nickel complexes of dithio-/ -diketones are dominated by fragmentation products of the uncomplexed oxidized ligand, which is consistent with the low stability of dithio-/J-diketones and the greater stability of the 1,2-dithiolium... 

The complementary structural information of both NMR spectroscopy and MS detection is particularly valuable for the analysis of closely related glycosidic natural products, where compounds of the same molecular mass (isobars, see Table 5.1.1), and even with identical MS/MS fragmentation patterns, frequently occur, as this example demonstrates. 

These related alkaloids were obtained from Popowia pisocarpa (Bl.) Endl. (An-nonaceae). Pisopowine (504), C40H4gN2O6, amorphous, [aft —152° (c 0.4, MeOH), showed completely symmetrical H- and 13C-NMR spectra and a MS fragmentation pattern indicating identical head units. The structure was confirmed via ceric ammonium... 

Scheme 1. Major MS fragmentation pattern for L6-diene series (R = H, CH or TMS).

Schelhammericine (C19H23N03) was recognized as a Al(6)-alkene structure from its MS fragmentation pattern (see Section III,C,1) and structure 81a was determined through analysis of its NMR spectrum. Values of 3.5 and 5.0 Hz for J3A suggested that the proton at C-3 was equatorial. Schelhammericine was identified as the dihydro product 81a obtained on catalytic hydrogenation of schelhammeridine (refer to Scheme 21) 84). 

Recently, a GC-MS method for the separation and quantitative identification of extracts from Cephalotaxus species (97) has been described. Most of the alkaloids were resolved, particularly the biologically active esters. The seven Homoerythrina alkaloids were only resolved into two groups of five and two components, respectively, under the conditions described. Acetylcephalotaxine (106), 11-hydroxycephalotaxine (114), and desmethyl-cephalotaxinone (113) were not resolved by retention time, but could be identified within the mixture by their MS fragmentation patterns. Cepha-lotaxinone (112) gave two GC peaks after silylation, presumably due to a contribution from the enol component. The artifact peak overlaps partly with the peak for drupacine (115) and hence introduces a slight error for this component and makes it difficult to quantify cephalotaxinone. 

Although you might look at the MS fragmentation patterns to help determine the structure, this is more time-consuming than going on to other spectra. You can verify the fragmentation patterns more easily once you have a proposed stmcture. 

Figure 9.1.6 shows the mass spectrum of palmitic acid ethyl ester (12) (TIC retention time 18.94min, Scan No. 1145). The major MS fragmentation patterns of the compound are similar to those of palmitic acid, except that all of the important ion species in the spectrum have mass numbers 28 units higher than the corresponding ion species in the spectrum of palmitic acid (11) for example, ion species m/z 88, 101, 157, and 284 compared to ion species m/z 60, 73, 129, and 256 (Odham and Stenhagen 1972). 

Several studies of ms fragmentation patterns and their interpretation have appeared for opioids/411"414 including a comparison of spectra for B/C cis and B/C trans derivatives. A summary of these data has been published/473 The initial process under electron impact may be rationalized by the removal of an electron from the opioid nitrogen to give the molecular ion, followed by cleavage of a C—C bond /3 to nitrogen. 

Unlike the case for other chlorinated compounds such as PCBs, double charged ions (at m/z values < MG/2 and with only 1 u between the chlorine isotope peaks) have not been mentioned for toxaphene components. The analysis of the GC/EI-MS fragmentation patterns allows a partial structure elucidation and the confirmation of the presence of a bornane skeleton. This knowledge facilitates a further structure elucidation by H-NMR spectroscopy [111]. 

STAT generated based on parent ion mass. Mass of MS" fragmentation pattern matched to fragmentation of reference structures. 

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