Mass spectra of some steroidal diols

The mass spectral fragmentations of a number of steroidal 3,5- and 4,5-diols and some derivatives have been examined using high resolution mass spectrometry and deuterium labelling. Although the 3,5- and 4,5-diols have very similar mass spectra those of the derived ketols are quite characteristic. A pathway for the formation of the important m/e 332 ion in the mass spectrum of cholestan-4β,5α-diol has been postulated.     

Electron-impact fragmentation of N-substituted 2-aminobenzoxazoles and 2-aminobenzothiazoles

The mass spectra of twenty-eight N-substituted 2-aminobenzoxazoles and 2-aminobenzothiazoles have been recorded and the identity of various ions in the mass spectra have been established by high resolution measurement. The molecular compound of series, benzoxazole, undergoes loss of hydrogen cyanide and carbon monoxide from the molecular ion as the most important decomposition pathways. The mass spectra of N-substituted benzothiazoles showed a similar fragmentation as that of N-substituted benzoxazoles.     

The mass spectra and ionization potentials of the neutral fragments produced during the electron bombardment of aromatic compounds

A mass spectrometer equipped with a dual ionization chamber ion source has been used to characterize directly the neutral species produced in the dissociative ionization of gases by electron impact. Neutral fragment mass spectra have been obtained for the electron ionization and fragmentation of benzene, toluene, o-xylene, m-xylene, p-xylene, mesitylene and isotopically labeled toluene. The neutral fragment mass spectra correlate well with the structures of the molecules. The abundant species in the neutral fragment mass spectra also correlate reasonably well with the abundant complementary positive ions of the normal mass spectra. Ionization potentials have been determined for the abundant neutral species produced. Where comparisons with values reported elsewhere are possible, the agreement is usually within ±0.2 eV or less.     

Rearrangement reactions in the positive and negative ion mass spectra of clausmarin A

The positive and negative ion mass spectra of clausmarin A, a naturally occurring tetracyclic coumarin, have been studied. The base peaks in the positive and negative ion spectra correspond to the complementary ions at m/z 143 and m/z 255, respectively, formed by a rearrangement reaction. The fragmentation pathways have been elucidated with the help of exact mass measurements and in situ deuterium labelling.     

Mass spectra of Sceletium alkaloids

The mass spectra of several naturally occuring Sceletium alkaloids, as well as several synthetic variants, have been investigated. Techniques used include high resolution mass measurements, analysis of metastable transitions by the technique of ion defocusing and specific deuterium labeling in conjunction with low resolution mass spectrometry. Characteristic major fragmentation pathways have been determined for four basic structure types studied: the cis-3a-aryl-octahydroindole ring system, exemplified by mesembrine; its 2,3-pyrido analog, Sceletium A₄; the seco series of pyridine bases, represented by tortuosamine; and the seco analog of the mesembrine-type represented by tortuosamine; and the seco analog of the mesembrine-type represented by dehydrojoubertiamine.     

Electron impact induced cyclizations in 4-chioro-3-(N-aryliminomethyl) (2H) benzopyrans and benzothiopyrans

Intramolecular substitutions leading to cyclizations with the ejection of chlorine have been noticed during mass spectral fragmentation of 4-chloro-3-(N-aryliminomethyl) (2H) benzopyrans and benzothiopyrans. Very interesting ortho effects involving intramolecular substitutions have also been observed in 6-methyl-4-diloro-3-[N-(2-methoxyphenyliminomethyl)] (2H) benzopyran and 6-methyl-4-chloro-3-[N-(2-chlorophenyliminomethyl)]-(2H) benzopyran. The proposed fragmentation mechanisms have been supported by the accurate mass measurements and linked scan studies.     

Photoionisation and fragmentation of the stereoisomers of 4-t-butylcyclohexyl acetate and 4-t-butylcyclohexyl methyl ether

The fragmentation of the stereoisomers of 4-t-butylcyclohexyl acetate and 4-t-butylcyclohexyl methyl ether has been studied by photoionisation mass spectrometry at 1216 Å and 584 Å. Deuterium substitution and high resolution mass spectrometry have been used to gain further insight into the fragmentation pathways.     

Mass analysis of overlapping ion kinetic energy peaks arising from charge separation in dications

A triple-sector instrument of reversed geometry, BEQQ, has been employed to resolve overlapping ion kinetic energy peaks arising from charge separation of metastable dications. Separation was achieved through mass resolution of the dication in the magnetic sector and of the singly charged product ion of greater mass in the quadrupole mass filter accompanied by energy resolution with the electric sector; the electric sector was scanned to cover the complete range of each charge separation peak. Two overlapping ion kinetic energy peaks arising from charge separation of the diphenylenimine dication and up to four overlapping ion kinetic peaks arising from charge separations of dications arising from benzene-1,3,5-d₃ have been resolved. The kinetic energy releases have been calculated in each case. Enhanced z-discrimination is observed with the final stage of mass analysis.     

Mass spectra of pyridine monoamidoximes and their O-trimethylsilyl ether derivatives

The mass spectra of pyridine-2-, -3-, and -4-amidoxime and their O-trimethylsilyl derivatives have been investigated. Also included in this study were the deuterated derivates. Main pathways of fragmentation of these compounds have been proposed. A comparison with the mass spectra of the corresponding pyridine aldoximes has been made.     

Transport processes in the sorption of colored ions by peat particles

A three-step model has been proposed for the adsorption of Astrazone Blue dye (Basic Blue 69) on peat. The initial rate of uptake of dye ions due to physical adsorption and chemisorption (ion exchange) has been correlated using a surface mass transfer coefficient. These coefficients have been determined and expressed in the dimensionless mass transfer form, Sh/Sc^0.33, as a function of agitation, initial dye concentration, peat particle size range, dye solution temperature, and mass of peat.     

N′,O,O′-triacetyl-N-caffeoylputrescine: A new synthesis and mass spectrometry

Some puzzling features of a published mass spectrum of the title compound have been clarified by mass spectrometric study of a specimen prepared by a new route, by coupling O,O′-diacetylcaffeoyl chloride with N-monoacetylputrescine.     

Mass spectral studies of stereoisomers: The photoionisation of some substituted cyclohexanols

The fragmentation of the stereoisomers of 4-t-butylcyclohexanol, and 3-methylcyclohexanol has been studied by photoionisation mass spectrometry at 1216 Å and 584 Å. Deuterium substitution and high resolution mass spectrometry have been used to gain further insight into the fragmentation pathways.     

Advantages of high-resolution and high-mass range magnetic-sector mass spectrometry for electrospray ionization

Electrospray ionization (ESI) mass spectra have been measured on a magnetic-sector double-focusing mass spectrometer for a number of proteins and peptides. It is pointed out how in theory raising the mass resolution of a mass spectrometer from 800–1000 to 2400–3000 significantly increases the precision with which the envelope of isotopic peaks of a protein ion (or other organic ion) can be defined, particularly at higher masses. Better definition of the isotopic envelope ought to lead to higher precision in the experimental determination of molecular mass, which has been demonstrated. It is shown how ESI mass spectra of high-mass molecules are significantly less congested at higher m/z values, so that for these molecules (RMM > 40 000) there is an advantage in being able to record peaks at higher m/z values (m/z > 2000) representing ions with fewer charges. Fragmentation of a small peptide in the ESI source has been found to provide sequence information.     

Unexpected mass spectral skeletal rearrangements in aromatic thioamides

Interesting skeletal rearrangements, resulting in the formation of unexpected fragments, have been noticed in the mass spectra of aromatic thioamides of cyclic amines such as piperidine, morpholine and pyrrolidine. Suitable mechanisms, based on mass analysed ion kinetic energy spectra, high voltage scan spectra and high resolution data, have been proposed for the formation of [M? SH]⁺ ions and the fragment at m/z (103+R) in the mass spectra of these compounds. The mass spectra of the thioamides of non-cyclic amines and the thioamides of aliphatic acids contain peaks corresponding to a four-centred skeletal rearrangement followed by the elimination of either the thioalkoxy or the thiophenoxy radical from the molecular ions.     

Mass spectrometry of p-toluenesulfonamides: Useful amine identification derivatives

The mass spectral fragmentation patterns of p-toluenesulfonamides have been determined and have been found useful for identification of naturally occurring amines.     

Mass spectrometry: XI—Electron impact induced fragmentation of some amides of F-acids and their deuterated homologues

The mass spectrometry of perfluoro compounds (F-alkyl compounds) has seldom been the subject of systematic studies. Fluorocarbons excepted, only a few mass spectra of such compounds have been analysed and corresponding fragmentations correlated. In this paper we report the mass spectra of 19 amides of perfluoro acids (R_FCONHR) with R=benzyl, 2-phenylethyl, 2-phenylpropyl, 3-phenylpropyl, 2-(N-phenylamino)ethyl, and R_F=F-methyl, n-perfluoropropyl, n-perfluoropentyl and n-perfluoroheptyl. These compounds exhibit quite different behaviour from their hydrocarbon homologues under electron impact (for instance no [R_FCO]⁺ fragment was found). Specific deuterium labelling and high resolution measurements have been used to show typical rearrangements and to establish the fragmentation routes.     

Electron-impact induced fragmentation of dimethanonaphthalene-type compounds

The mass spectra of endo,endo-1,2,3,4,4a,5,8,8a-octahydro-1,4:5,8-dimethanonaphthalen-anti-2-01 (Ia) and its endo,exo-2-ol (IIa) and endo,exo-10-ol (IIIa) isomers have been examined. Fragmentation schemes have been constructed on the basis of metastable transition measurements, accurate mass determination and deuterium substitution. A presence of the double bond in the molecule and a favourable hydrogen atom orientation in the vicinity of the double bond play an important role in the ion degradation process.     

Mass spectra of the bitter principles fromPicrasma ailanthoides Planchon

The mass spectra of several bitter principles isolated from Picrasma ailanthoides Planchon (= P. quassioides Bennett) have been measured and characteristic fragmentation patterns useful for structure elucidation shown. The mass spectra of some related compounds are also described.     

Mass spectra of branched long-chain aliphatic alcohols

The mass-spectral behaviour of long-chain aliphatic primary alcohols of the normal, iso-and anteiso-series have been discussed. The mass-spectral fragmentation of individual alcoholic types have been found to be structurally specific. The mass spectra of some deuterio derivatives have shown, however, the complicated nature of the fragmentation processes.     

Understanding the Fragmentation Pathways of Carbocyclic Derivatives of Amino Acids by Using Electrospray Ionization Tandem Mass Spectrometry

Aminoacyl derivatives of aminoadamantanes amantadine and rimantadine have been investigated in regard to their antiviral properties. So far, few studies on the mass spectrometric fragmentation pathway of these compounds have been reported using high-resolution mass spectrometry (HRMS). Two major fragmentation pathways have been observed. For the rimantadine derivatives, losses of rimantadine and N-(1-adamantyl) ethylformamide were described. Similarly, in case of amantadine derivatives, there were losses of amantadine and N-(1-adamantyl) formamide. The loss of the aminoacyl group was common to all of the studied compounds. Understanding the fragmentation mechanism can bring new insight into the characterization of these compounds.