Hydrogen mass spectra

A stirred light yellow suspension is slowly heated to 130-140°. At about 90° a slow gas evolution takes place and a yellow solution is formed. After 24-26 h at 130° the reaction is complete and 4.74 L [100%, STP (standard temperature and pressure)] pure hydrogen (mass spectrum) are collected in the gasometer. Ethene gas is bubbled through the colorless solution for nearly 30 min at about 60° (bath) to destroy quantitatively the last amounts of (9H-9-BBN)2 ( B, (5 27). The solvent is distilled off under reduced pressure (0.001 torr, bath < 60°) and the solid residue is sublimed (bath 85-5 110°/... 

Not only the molecular ion peak but all the peaks m the mass spectrum of benzene are accompanied by a smaller peak one mass unit higher Indeed because all organic com pounds contain carbon and most contain hydrogen similar isotopic clusters will appear m the mass spectra of all organic compounds... 

In a mass spectrum, the ratios of isotopes give a pattern of isotopic peaks that is characteristic of a given element. For example, the mass spectrum of any corn ound containin carbon, hydrogen, nitrogen, and oxygen will show patterns of peaks due to the, 7C, 7N, gO, gO, and... 

The mass spectrum of 2-pyrone shows an abundant molecular ion and a very prominent ion due to loss of CO and formation of the furan radical cation. Loss of CO from 4-pyrone, on the other hand, is almost negligible, and the retro-Diels-Alder fragmentation pathway dominates. In alkyl-substituted 2-pyrones loss of CO is followed by loss of a hydrogen atom from the alkyl substituent and ring expansion of the resultant cation to the very stable pyrylium cation. Similar trends are observed with the benzo analogues of the pyrones, although in some cases both modes of fragmentation are observed. Thus, coumarins. 

On the other hand, a metastable-ion peak at m/e 88.1 (calculated, 88.0) is present in the mass spectrum of 11 (Figure 8) for the formation of m/e 129 from m/e 189, by loss of acetic acid. In the mass spectrum of the D20-exchanged analog, m/e 129 partially shifts to m/e 130 and partially stays at m/e 129. Metastable-ion peaks are also present at m/e 154.8 (calculated, 154.7) and m/e 97.3 (calculated, 97.3) for the loss of water from m/e 189 followed by the loss of ketene, to give an ion at m/e 129. Since m/e 171 from the loss of water remains at m/e 171, the loss of water must involve the hydroxyl hydrogens. Scheme 3 is an attempt to summarize this in terms of structures which are entirely... 

The mass spectrum of 2-methylbenzaldehyde suggests an aromatic compound because of the intensity of the molecular ion and peaks at m/z 39, 51, and 65 (see Figure 6.2). The loss of hydrogen atoms and loss of 29 Daltons from the molecular ion indicate that this is an aromatic aldehyde. Looking up m/z 91 in Part III suggests the following structure ... 

Analysis of ibuprofen, the active ingredient in several over-the-counter pain relievers, shows that it contains 75.7% carbon, 8.8% hydrogen, and 15.5% oxygen. The mass spectrum of ibuprofen shows that its molar mass is less than 210 g/mol. Determine the chemical formula of this compound. 

Supersonic molecular beam (SMB) mass spectrometry (SMB-MS) measures the mass spectrum of vibra-tionally cold molecules (cold El). Supersonic molecular beams [43] are formed by the co-expansion of an atmospheric pressure helium or hydrogen carrier gas, seeded with heavier sample organic molecules, through a simple pinhole (ca. 100 p,m i.d.) into a 10 5-mbar vacuum with flow-rates of 200 ml. rn in. In SMB, molecular ionisation is obtained either through improved electron impact ionisation, or through hyperthermal surface ionisation... 

Scheme 14 Top Plausible catalytic cycle as supported by deuterium labeling. Bottom ESI mass spectrum of a reaction mixture aliquot diluted 5000-fold in methanol from the hydrogen-mediated coupling of gaseous acetylene to an a-ketoester (Ar = p-N02Ph)...

Schmitt [17] in his book on the analysis of surfactants includes details of a number of HPLC-based procedures. LC-MS can be used for positive identification. Figure 29 shows the molecular ion mass spectrum for the surfactant lauryl hydrogen sulfate detectable as its (M—H) ion by positive ESI. 

Figure 29 Mass spectrum for lauryl hydrogen sulfate (positive ESI).

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>. 

Compound 172 exhibited typical indolenine UV absorptions and mass Spectral fragmentation very similar to those of 15,20-anhydrocapuronidine (303), obtained by concentrated H2S04 dehydration of 170. Upon reduction with NaBH4, the indolenine 172 was converted to its 1,2-dihydro derivative, identical to the natural product 173. Catalytic hydrogenation gave a tetrahydro derivative, characterized by a peak at m/z 190 in the mass spectrum, typical of pseudoaspido-spermatane alkaloids. 

M — H]+ ion is observed in the mass spectrum, the carbon atom linked to this hydrogen is not linked to any alkyl group. 

Fig. 2.12.6. Identification of esterquat compounds FIA-APCI-MS-MS(+) (CID) product ion mass spectrum of selected [M — RCO]+ base peak ion of cationic surfactant blend of di-hydrogenated tallowethyl hydroxyethyl ammonium methane sulfate type (mlz 692 general formula (R(C0)0CH2CH2)2-N (CH3)-CH2CH2(0H)CH30S03) fragmentation behaviour under CID...

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