Zum Mechanismus massenspektrometrischer Fragmentierungsreaktionen—IXSterische Effekte in den Massenspekten der Stereoisomeren von Decalin-2,3-diolen,Decalin-2,4-Diolen und Ihen Dimethyläthern

The mass spectra of all stereoisomers of decalin-2,3-diol, the corresponding dimethyl ethers and of some deuterated derivatives are discussed. The mass spectra of isomeric decalin-2,3-diols differ only slightly in ion intensities. The mass spectra of the stereoisomeric 2,3-dimethoxy-decalins are nearly identical within the series of transand cisderivatives. A mass spectrometric identification of the stereoisomers of these compounds is therefore diffucult. Stereoselective eliminations from the molecular ion are not observed. The mass spectra -of stereoisomeric decalin-1,4-diols show characteristic differences in the intensities of the[M ? H₂O]⁺˙-ions, which can be related to the geometry of the molecules in a similiar mode as was the case with cyclohexane-1,4-diols, The sterechemical control of the elimination of H₂O from the molecular ions has been confirmed by deuterium labelling. The mass spectra of stereoismeric 1,4-dimethoxy-decalins also differ characteristically in the intensities of the [M ? CH₃OH]⁺˙ ions. Furthermore peak due to the [M ? CH₂O]⁺˙ ions are only observed in the mass spectra of those stereoisomers, which have at least one conformation with a short distance between the two methoxy. The stereospecifity of the CH₃OH- and CH₂O-eliminationjs has also been determined by deuterium labelling.     

Low-energy mass spectra of some aliphatic ketones

The charge exchange mass spectra of a selection of C₅-C₇ ketones have been measured using [CS₂]⁺˙, [COS]⁺˙ and [N₂O]_+. as reagent ions. The low energy charge exchange with [CS₂]⁺˙ or [COS]⁺˙ provides simple primary ion mass spectra, which readily permit structure elucidation in contrast to metastable ion spectra. In several cases, isomer distinction is easier from the charge exchange mass spectra than from the electron impact mass spectra. The energy transfer from [N₂O]⁺˙ is sufficiently high for complex spectra resembling electron impact mass spectra to be obtained.     

Synthesis and Spectroscopic Characterization of a Complex of 1, 10‐Phenanthroline with Magnesium

The complex [Mg(1, 10‐phenanthroline)₃(NO₃)₂]·9H₂O has been synthesized. It forms crystals having the shape of sheaves with very thin filaments. The compound has been characterized by UV, IR, NMR and mass spectra. The UV and mass spectra are indicative of an electron density transfer from NO₃^— to Mg²⁺. On the base of the spectroscopic studies a model of the crystal structure has been proposed.     

Structure and formation of [C4H6N]+ ions: 1—Ion structures derived from aliphatic nitriles

Structures and formation of the [C₄H₆N]⁺ ions present in the mass spectra of eleven α-substituted and eleven α-unsubstituted nitriles have been investigated from collisional activation and metastable ion spectra. Collisional activation spectra lead to identification of six structures. The [C₄H₆N]⁺ ions from some branched compounds prove to be mixtures. This, as well as the identity of all metastable ion parameters and certain spectral data, shows that energy differences between all structures are small. This is corroborated by MINDO/3 calculations showing a spread from 724 to 891 kJ mol^?1 over the structures. Earlier proposals for two different [C₄H₆N]⁺ ion structures, based on the mass spectra of deuterium labelled compounds, appeared to be correct. A computer program to calculate the contribution of standard spectra in a measured spectrum has been developed.     

The field desorption mass spectra of some oligosaccharides and their permethylates and peracetylates

Field desorption mass spectra have been obtained for a number of di-, tri- and tetrasaccharides, and for some permethyl and peracetyl derivatives. The free sugars usually show intense [M + 1]⁺ ions thus enabling the determination of molecular weights. The effect of variation of emitter current on the relative intensities of fragment ions has been investigated. Permethylated oligosaccharides show intense molecular ions; in contrast peracetylated oligosaccharides show only weak molecular ions but strong [M ? 60]⁺ ions. Information from electron-impact and field desorption mass spectra is essentially complementary.     

Electron-impact studies—LXXIV: A survey of rearrangement processes in the ‘doubly-charged ion’ mass spectra of aromatic compounds

The technique of Beynon² has been used to determine the ‘doubly-charged ion’ mass spectra of a variety of aromatic compounds which contain pronounced rearrangement peaks in their conventional mass spectra. Many, but not all, of the ‘doubly-charged ion’ spectra contain similar rearrangement peaks to those observed in conventional spectra.     

The Mass Spectral Studies of Halogenated Vinyl Methanesulfonates

The mass spectra of saturated sulfonate esters^1,2) have been reported recently. No study has been made on the vinylic methanesulfonates. In order to understand their breakdown patterns, several chloro- and fluoro-containing vinyl methanesulfonates have been made³⁾ and their mass spectra studied. The chlorine compounds are chosen because the natural abundance of isotope ³⁵Cl and ³⁷Cl can serve as a internal tag. The vinyl methanesulfonates containing electronegative fluorine are used as a comparison to the chloro-compounds because of their similar electronegativities.     

Mass spectrometry of steroid systems

Summary 1. The mass spectra of epimeric tertiary alcohols of the D-homoestrane series and the acetates and 17a-trideuteromethyl analogs corresponding to them have been studied. A new approach to the determination of the configuration of tertiary steroid alcohols has been proposed in which the trideuteromethyl analogs of the epimeric alcohols are subjected to mass-spectrometric analysis. The presence in the mass spectrum of an epimer of a doublet of peaks M-H₂O and M-DOH indicates the a-alkyl-e-OH configuration, while the presence in the spectrum of an intense M-H₂O peak shows the presence of an axial OH group.2. The mass spectra of the epimeric secondary alcohols of the pregnane series taken with the use of a system of introducing the sample into the ion source has been investigated. It has been shown that the mass spectra of alcohols containing an a-OH group in rings C and D differ markedly from the spectra of the e-OH epimers with respect to the ratio of the intensities of the peaks M-H₂O and M⁺.Khimiya Prirodnykh Soedinenii, Vol. 3, No. 6, pp. 369–382, 1967     

The structure of tetramycin,a new polyene macrolide antibiotic

The structure of the tetraene antifungal antibiotic tetramycin has been established by detailed studies of mass, ¹H and ¹³C NMR spectra as well as by chemical degradation. A newly developed mass analysis has been introduced for determining the carbon skeleton of the aglycone.     

Chemical ionization mass spectra of 2, 4, 6-trinitroaromatic compounds

The methane and isobutane chemical ionization mass spectra of ten 2,4,6-trinitroaromatic compounds have been recorded. The mass spectra contain intense [M + 1]⁺ ions and usually little fragmentation. However, in some cases major fragmentation processes have been observed. Some unusual adduct ions have been found with isobutane as the reagent and their temperature dependence has been studied.     

Stereospecific adduct ion formation in the chemical ionization mass spectra of E- and Z-1,2,3-triaryl-2-propen-1-ones

Stereospecific adduct ion formation has been observed in the chemical ionization mass spectra (positive and negative) of certain E- and Z-1,2,3-triaryl-2-propen-1-ones. The Z isomers are found to give higher relative abundances of adduct ions than the E isomers. This has been interpreted in terms of the differences in the proton affinities of the isomers originating from their different degrees of enone resonance. Halide ion (CI^? and Br^?) attachment spectra of these compounds also show stereochemical differences in the relative abundances of [M]^?˙ and [M+halide]^? ions, though the effect is not as pronounced as in the case of the positive ion spectra.     

Template synthesis and spectroscopic characterization of 16-membered [N4] Schiff-base macrocyclic complexes of Co(II), Ni(II), Cu(II), and Zn(II): in vitro DNA-binding studies

Template condensation between o-phthalaldehyde and 3,4-diaminotoluene resulted in mononuclear 16-membered tetraimine macrocyclic complexes, [MLCl₂] [M?=?Co(II), Ni(II), Cu(II), and Zn(II)]. The proposed stoichiometry and the nature of the complexes have been deduced from elemental analyses, mass spectra, and molar conductance data. The macrocyclic framework has been inferred from ν(C=N) and ν(M–N) bands in the IR spectra and the resonances observed in ¹H and ¹³C-NMR spectra. Octahedral geometry has been assigned for all these complexes on the basis of position of the bands in electronic spectra and magnetic moment data; distorted octahedral geometry has been assigned for the Cu(II) complex on the basis of EPR data. The low-conductivity data of all the complexes suggest their non-ionic nature. Interaction of these complexes with calf-thymus DNA (CT DNA) has been examined with fluorescence quenching experiments, which show that the complexes are avid binders of CT DNA.     

Mass spectra of π-cyclopentadienyl-diene cobalt complexes

Many reports on the mass spectra of organotransition-metal complexes have appeared in recent years,¹ whilst there have only been a few reports on the mass spectra of transition metal olefin complexes, some metal carbonyl olefin complexes²³⁴ and π-cyclooctenyl-π-cyclooctadienyl cobalt.⁵ Recently fragmentation paths of π-cyclopentadienyl-cyclooctadiene rhodium were elucidated by King.⁶ The present authors found metastable ions in the mass spectra of π-cyclopentadienyl-diene cobalt complexes as well as in the mass spectra of π-cyclopentadienyl-diene rhodium complexes.⁷. In the present paper the authors wish to report the mass spectra of several π-cyclopentadienyl diene cobalt complexes.     

Mass spectra of arylhydroxyoximes and their complexes with transition metals

The EI mass spectra of several arylhydroxyoximes and of their coordinated complexes with transition metals, Cu, Ni, Co and Fe have been studied using high resolution mass spectrometry, metastable ion measurements and the stable isotopes ¹⁵N, ⁶³Cu and ⁶⁵Cu labelling to elucidate the fragmentation pathways. It has been found that the spectra of all compounds 1–24 except Fe-complex 24 show molecular ions. The relative intensity of molecular ions of the complexes, which contained the same kind of metal and the arylhydroxyoximes with different substituents R , is closely related to the electronegativity of R. In all metal-complexes 9–22 , the main decomposition pathways involve the successive loss of O, NO and then H₂O or LH. In these spectra the fragment ions of non-metal- containing species resulting from the cleavage of the dioxime ligands can be discriminated.     

Study of adduct ions of meso-phenyl-substituted tetrabenzoporphyrins by fast-atom bombardment mass spectrometry

Mass spectra of meso-phenyl-substituted tetrabenzoporphyrins were investigated by fast-atom bombardment mass spectrometry and tandem mass spectrometry. A cluster of adduct ions with mass-to-charge ratio values higher than the corresponding molecular ions of the porphyrins has been observed. The mass number differences among the series of cluster ions are constant depending on the para-phenyl substituents. Under certain conditions, dimers or trimers of molecular ions with low abundances have been detected. To trace the origin of the adduct ions, a series of experiments based on mass spectrometry have been carried out. The mass spectrum of tetrabenzoporphyrin showed no adduct ions with mass number differences of 90 even with the addition of phenylacetic acid. The mass spectrum of meso-tetraphenylte-trabenzoporphyrin ¹³C-labeled at the meso carbons showed adduct ions with mass number differences of 91. Product spectra of [2M + H]⁺ or [3M + H]⁺ of porphyrins exhibited adduct ions. All these results suggest that fragmentations of [2M + H]⁺ or [3M + H]⁺ may be one of the many possible routes to form the adduct ions, and the mass number differences among the series of these cluster ions should correspond to the benzyl group from the meso positions of meso-phenyl-substituted tetrabenzoporphyrins.     

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.     

Analyse par Spectrometrie de Masse de Derives Fluores en Serie Pyrimidine et Pyrazine

Fluorinated derivatives of trichloro- and dichloropyrimidines and dichloropyrazines have been synthetised and analysed by ¹H and ¹⁹F n.m.r. in association with gas chromatography coupled with mass spectrometry. The behaviour of the compounds under electron-impact is presented and discussed. Attention has been drawn to different mass spectra for distinct positional isomers, confirming the main degradation schemes proposed.     

Chemical ionization and electron impact mass spectra of thiosulfinates,thiosulfonates and sulfinyl sulfones

The chemical ionization and electron impact mass spectra of some thiosulfinates, thiosulfonates and sulfinyl sulfones have been studied. The electron impact mass spectra of four of the six thiosulfonates show molecular ions of less than 1%. Inconclusive evidence was obtained for sulfenyl sulfinate type intermediates in the electron impact spectra of thiosulfonates. The electron impact spectra of thiosulfonates were similar to those of thiosulfonates. The chemical ionization (isobutane) mass spectra of thiosulfinates and thiosulfonates generally show protonated molecular ions [MH]⁺ as base peaks and [MH+1]⁺ and [MH+2]⁺ peaks.     

The modern mass spectrometer—a complete chemical laboratory

Using nitrobenzene as an example, various ways in which a contemporary mass spectrometer can be utilized to yield a wealth of information about the compound studied are reviewed. Applying a variety of different techniques and procedures, in addition to the conventional low resolution mass spectrum, the following nitrobenzene spectra have been obtained: collision induced dissociation mass spectrum, mass analysed ion kinetic energy spectra, collision induced dissociation mass analysed ion kinetic energy spectra, spectra obtained at constant B/E, spectra obtained at constant B²/E, high voltage scans of metastable ion fragmentation processes, consecutive fragmentations in different field free regions, charge exchange mass spectra, charge stripping mass spectra, doubly charged ion mass spectra, chemical ionization mass spectra, negative ion mass spectra, negative ion mass analysed ion kinetic energy spectra, negative ion mass analysed ion kinetic energy collision induced dissociation spectra, charge inversion spectra, etc. The complementary types of information available from the above studies are discussed to show the unique versatility of mass spectrometry as a technique for the examination of organic compounds.     

The observation of broad metastable ion peaks in the surface-induced dissociation mass spectra of protonated and cationated peptides

The product ion mass spectra of protonated and cationated peptides of relative molecular mass (RMM) 555–574 Da have been obtained by surface-induced dissociation of MH⁺ and [M + Cat]⁻ ions in a four-sector tandem mass spectrometer equipped with a specially designed collision cell. A linked scan of the electric and magnetic sector field strengths of the second mass spectrometer was used to transmit the fragment ions arising from collisions with a stainless steel surface. The resulting mass spectra contained broad metastable ion peaks produced by the dissociation of MH⁺ and [M + Cat]⁺ ions before the second magnetic sector, in the fourth field-free region of the instrument.