Mass spectrometry of pyrazolium salts

A series of pyrazolium bromides were investigated by field desorption, field ionization and electron impact mass spectrometry. Dealkylation was found to be the predominant thermal decomposition. The nature of the substituents controls the pyrazole formed. The application of field ionization was found to facilitate the interpretation of the thermolytic decomposition products. Field ionization and electron impact mass spectra of N-phenylpyrazole and N-benzylpyrazole were obtained.     

Mass spectrometry of volatile mercury salts

The integrated ion current method is applied to the determination of mug quantities of mercury(II) chloride. The mass spectra of both mercury(I) and (II) chlorides indicate that the analytical reagent grade chemicals contain traces of mercury(II) bromide and iodide.     

Mass spectrometry of the simple N- vinylpyridinium salts

N- Vinylpyridinium halides readily undergo a Hofmann type elimination, prior to evaporation in the mass spectrometer, with formation of pyridine, acetylene and hydrogen halide as volatile products. A second important reaction is thermally induced two electron reduction of the cation to the volatile N-vinyldihydropyridine. Of minor importance is the formation of volatile compounds with the elemental composition of [cation + C₂H] and [cation + C₂H₃]. The latter is suggested to have a divinyldihydropyridine structure. Its formation is explained as due to nucleophilic attack on the cation by the N-vinyldihydropyridine present with displacement of pyridine.     

Mass spectrometry of pyrylium salts. Free radical evaporation

From ionisation potential measurements it is shown that 2,4,6-triphenylpyrylium and thiopyrylium cations are thermally reduced in the mass spectrometer to the corresponding free radicals during evaporation of the bromides, iodides and fluoroborates. For the fluoroborates minor amounts of a fluoride adduct were also present. Perchlorate salts led to oxidation. The gaseous species from 2,6-diphenyl-4-methylpyrylium iodide consists of the anhydro base and hydrogen iodide.     

Mass spectrometry of arenediazonium salts by fast atom bombardment

Contrary to expectation, thermally labile arenediazonium salts (M) afford sizeable peaks due to ArN₂ ⁺ and (ArN₂ ⁺)M ions under fast atom bombardment; the main fragment ion is usually the highly reactive aryl cation Ar⁺, the production of which is independent of whether its ground state is singlet or triplet.     

Mass spectrometry of onium compounds—IV: Diazonium salts

The zwitterions of diazotized ortho and para aminophenol are very volatile and give strong peaks in the mass spectra corresponding to the molecular ion. The m-isomer, which cannot be stabilized through a simple quinonoid structure, gives rise to a complex spectrum through decomposition and coupling reactions. The zwitterions of diazotized anthranilic and sulphanilic acids did not give the molecular ion peak.     

Mass spectrometry of some triphenylcyclopropenium salts. Competition between dimerisation and adduct formation

The triphenylcyclopropenium chloride, bromide and iodide evaporate in the mass spectrometer mainly as the covalent cation-halide adduct, the fluoroborate as the corresponding fluoride adduct and boron trifluoride. In addition di-3,3′-triphenylcyclopropene is formed, presumably via triphenylcyclopropenyl radicals.     

Mass spectrometry of nanodiamonds

Detonation nanodiamonds (NDs) were studied by time‐of‐flight mass spectrometry (TOF MS). The formation of singly charged carbon clusters, C, with groups of clusters at n = 1–35, n ∼160–400 and clusters with n ∼8000 was observed. On applying either high laser energy or ultrasound, the position and intensity of the maxima change and a new group of clusters at n ∼70–80 is formed. High carbon clusters consist of an even number of carbons while the percentage of odd‐numbered clusters is quite low (≤5–10%). On increasing the laser energy, the maximum of ionization (at n ∼200 carbons) is shifted towards the lower m/z values. It is suggested that this is mainly due to the disaggregation of the original NDs. However, the partial destruction of NDs is also possible. The carbon clusters (n ∼2–35) are partially hydrogenated and the average value of the hydrogenation was 10–30%. Trace impurities in NDs like Li, B, Fe, and others were detected at high laser energy. Several matrices for ionizing NDs were examined and NDs themselves can also be used as a matrix for the ionization of various organic compounds. When NDs were used as a matrix for gold nanoparticles, the formation of various gold carbides Au_mC_n was detected and their stoichiometry was determined. It was demonstrated that TOF MS can be used advantageously to analyze NDs, characterize their size distribution, aggregation, presence of trace impurities and surface chemistry. Copyright © 2009 John Wiley & Sons, Ltd.     

Mass spectrometry of hexuronosyldiglycerides

Conclusions The fragmentation under electron impact of the molecular ions of synthetic methyl esters of 1,2-di-O-acyl-3-O-(2',3',4'-tri-O-acetyl--D-glucopyranuronosyl)-L-glycerides was studied. Mass spectrometry of such compounds gives extensive information on their structure.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 94–102, January, 1975.     

Mass spectrometry of hydroxystilbazoles

The mass spectral fragmentation of the six 2′-, 3′- and 4′ -hydroxy substituted 4- and 2-azastilbenes is discussed and fragmentation pathways, elucidation of which were assisted by accurate mass measurements and metastable transitions, are proposed. It has been found that the position of the hydroxystyryl group in the pyridine ring may be deduced on the basis of mass spectral fragmentation patterns.     

Mass spectrometry of methyltetrazoles

The mass spectra of tetrazole, all isomers of monomethyl- and dimethyltetrazole, several trifluoromethyl substituted tetrazoles, as well as deuterated analogs, were recorded. Loss of N₂ was the important fragmentation of the molecular ions of tetrazole and 2-methyl substituted tetrazoles; however, HN₂ loss was more important for 1-methyl substituted tetrazoles. The 1-methyl-tetrazoles showed molecular ion peaks while the 2-methyltetrazoles exhibited an unprecedented [M + 1] peak with no molecular ion.     

Mass spectrometry of proteins

Several of the present mass spectrometric techniques have sufficient mass range and sensitivity to be viable alternatives or valuable supplements to traditional methods in protein chemistry. The precision of the molecular masses determined by mass spectrometry allows highly specific protein and peptide characterization as well as identification and localization of post translational modifications. In this article the principles and practical performance of the key techniques are discussed and examples of applications given.