Fragment peaks

The submitters report that this product solidifies when cooled and melts at 21-22 and that the product is stable when stored in a refrigerator. The product exhibits infrared absorption (carbon tetrachloride) attributable to C=0 stretching at 1810 and 1765 cm. and a proton magnetic resonance singlet at B 1.50 (carbon tetrachloride). The mass spectrum of the product exhibits the following relatively abundant fragment peaks m/e (relative intensity), 60(10), 59(99), 57(34), 56(86), 55(47), 50(21), 44(100), 43(30), 41(91), 40(27), and 39(61). 

In conclusion, SSIMS spectra provide not only evidence of all the elements present, but also detailed insight into molecular composition. Quasimolecular ions can be desorbed intact up to 15000 amu, depending on the particular molecule [3.17] and on whether an effective mechanism of ionization is present. Larger molecules can be identified from fragment peak patterns which are characteristic of the particular molecules. If the identity of the material being analyzed is completely unknown, spectral interpretation can be accomplished by comparing the major peaks in the spectrum with those in a library of standard spectra. 

No discussion of the fragmentation pattern of dithietes by mass spectroscopy has appeared. Only molecular and major fragmentation peaks... 

After the possible structures are obtained, predict their mass spectra by examining the mass spectra of similar structures. Also, the GC retention time may eliminate certain structures or isomers. Discuss these results with the originator of the sample to determine the most probable structure. With experience, it is usually possible to determine which fragment peaks are reasonable for a given type of structure. 

The field desorption mass spectra of 154-158 always showed the ions [M+ 1]+, [M + 2] + and [M + 3] + in addition to the molecular ions which were the base peaks. No fragment peaks were seen in the latter spectra. 

The result of combining these various components in the analysis of a 2-pg sample of TCDD is illustrated in Figure 7. An internal standard is given by a PFA fragmentation peak which is a known distance, 85 mmu (1 millimass unit or mmu = 10" atomic mass unit), from the TCDD peak. In its present form the MS-9-CAT system has a limit of detection for TCDD of about 1 pg. 

Even HALS compounds which absorb weakly at 337 nm can be analysed directly without matrix assistance, with the exception of the high-MW Hostavin N 30 (ca. 1500 Da), which fragments by direct laser desorption ionisation of intact molecules occurs only in the presence of a (dithranol) matrix. Direct laser desorption leads only to noncharacteristic, low-MW fragments. Hostavin N 20 leads to [M + H]+, [M + Na]+, [M + K]+ and some fragmentation peaks. MALDI-ToFMS of Tinuvin 765, which consists of a mono- and bifunctional sterically hindered amine, only shows the adduct peaks of the bifunctional amine apparently, the monofunctional amine is not ionisable. 

The mass spectra of compounds 1-14 have been discussed in CHEC-II(1996) <1996CHEC-II(8)733>. The mass spectra of all the new reported compounds displayed the corresponding molecular ions consistent with their respective molecular formulas. The mass spectra of the derivatives 17a (R1 = Ph, R2 = H) and 17b (R1=Ph, Rz = OMe) showed fragment peaks due to loss of (M-NO-CO), characteristic of sydnone-containing molecules, at m/z = 346 and 376, respectively <2002IJH287>. The other significant peaks were observed at m/z =187 and 217 due to the formation of 3-aryM-cyanosydnone. Similarly, in the mass spectrum of 25 <2002IJH287>, the peak at 324 was due to the loss of C02 from molecular ion and the peak at mlz = 171 was due to the formation of 3-cyanocoumarin. The molecular ion peak of the compound 24 (R1 =/-Bu, R2 = H) was observed at m/z = 368. 

The mass spectra of the derivatives of 17 typified by 26a, 26b, and 26c <2001IJB475> possessed the fragmentation peaks shown below along with the molecular ion peaks. The mass spectra of thiazino-triazinones 26a, 26b, and 26c were in conformity with the assigned stmcture. Similarly, the compound 21 <1998JHC293> showed a molecular ion peak at ml z = 273 (M+) and a fragmentation peak at m/z = 230 (M+-CONH) due to loss of-CONH group from the molecular ion. 

The high-resolution mass spectrum of compound 7 (R, R1 = H) shows that the molecular ion constitutes the base peak at m/z = 170 (100%) and suffers the cleavage of C-C and C-N with hydrogen transfer giving rise to different heterobicyclic ions <2003PS2055>. However, for compound 4, in addition to the expected molecular ion, the fragment peaks appeared at m/z = [M-28]+, [PhCN]+, [R]+, [ArN]+, and [Ar]+ <2000JPR342>. 

After this first step, where some samples are eliminated because they are not suited to the protocol, the positive ion mode is used to investigate haem, an iron porphyrin which is a blood marker. Spectra taken of the haem reference show that it can be detected due to [M]+ and [M+H]+ ions (respectively, at m/z 616.2 and 617.2), and also due to a large distribution of fragment peaks between m/z 350 and m/z 550 (Figure 15.12a). The same spectrum has also been obtained for haemoglobin leading to the conclusion that the presence of protein does not disturb the detection of haem. 

The checkers verified the absence of dichloroalkylphosphine and trialkylphosphine contaminants in this product by obtaining acceptable elemental analytical results and by measuring the mass spectrum of the product, which exhibits a molecular ion peak at m/e 152 (35C1) with abundant fragment peaks at m/e 110, 43, and 41. 

On a gas chromatography column, packed with Apiezon M suspended on Chromosorb P and heated to 70°, the product exhibits a single peak with a retention time of 23.2 minutes. The sample exhibits infrared absorption (CCI4 solution) at 3100, 3030, 2985, 1440, 1340, and 1235 cm. with n.m.r. singlets (CCI4 solution) at 3.45 (CHaBr) and 0.90 p.p.m. (cyclopropyl CHj). The mass spectrum of the sample has abundant fragment peaks at m/e 149, 147, 67, 41, and 39. 

Thietane 1,1-dioxide derivatives reportedly produce sulfur dioxide as well as a variety of other fragments. Peaks resulting from retro cycloaddition fragmentation such as CH2S and CH2S02 are never lacking. 

The TPSR spectrum has reactant peaks at m/e = 32, 16, 28, 27, 26, and 40 corresponding to the parent and fragment peaks of oxygen, ethylene, and argon, respectively. A product peak at m/c=44 begins to appear at temperatures above 423 K and corresponds to the parent ion of both eAylene oxide and carbon dioxide. Changing the feed to ethylene-d4 gives rise to new product peaks at m/e = 48 and m/e = 46 as well as the peak at m/e = 44. The former two peaks are indicative of ethylene-d4 oxide. 

Characterization of product is confirmed via H NMR, IR, and mass spectra. Mass spectra of all these isocyanides exhibit a parent ion of maximum intensity and characteristic fragmentation peaks. Mass spectroscopy is also a useful tool for detecting unreacted amine or formamide. Isocyanides decompose in acid and are soluble in hexane, THF, toluene, CH2CI2, CH3CN, and alcohols. 

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