Direct Analysis Of Daughter Ions Research Articles

Mass spectrometry of metastable ions from lagochiline-type diterpenoids

Low-and high-resolution mass spectra and spectra of metastable ions were studied using direct analysis of daughter ions (DADI) and metastable defocusing (MD) of lagochiline-type diterpenoids. Patterns in their fragmentation were found.

Multiphoton and electron impact ionization of azirines. Part II: 2,3‐diphenyl‐1‐azirine at 248 nm and 193 nm

AbstractMultiphoton ionization of 2,3‐diphenyl‐1‐azirine Is reported for nanosecond laser excitation at 248 and 193 nm and compared with electron impact ionization. The dependence of the ion intensity on the laser intensity shows that the formation of the parent ion and some of the more prominent fragment ions require the absorption of two photons per molecule. Other fragment ions are produced after the absorption of three photons. The results of the absorbed photon energy are corroborated by ionization and appearance energies obtained on calibrated electron impact ionization. Pure metastable ion spectra were obtained both by the defocusing method and by direct analysis of daughter ions produced by electron impact ionization and also by multiphoton ionization. The multiphoton absorption is shown to proceed via two different excitation pathways. A complete ionic decay scheme is given.

Dissociative ionization of substituted piperideines

The fragmentation of different alkyl(aryl) substituted piperideines [tetrahydro-pyridines] was studied by analyzing high-resolution mass spectra and DADI [Direct Analysis of Daughter Ions] spectra. It was shown that the retrodiene decomposition of the ring is suppressed by competing processes of elimination of ring substitutents. The nature of the substituents and their mutual disposition on the ring have a substantial influence on the extent of their cleavage from the ring.

A study of complex mixtures of natural substances by the defocusing and dadi methods. V. Steroid metabolites of the phytopathogenic fungusVerticillium dahliae

The mixture of steroid metabolites of the phytopathogenic fungusV. dahliae have been studied by high- and low-resolution mass spectrometry, metastable defocusing, and the direct analysis of daughter ions (DADI). On the basis of the analysis of the spectral results obtained for the mixtures themselves and for the products of their tosylation the presence in the samples studied of mixtures of β-sitosterol, stigmasterol, and cholesterol has been established. Probable structures have been proposed for the components of the mixture with m/z values of the molecular ions of 426, 424, and 412.

Mass spectra and dadi spectra of arylidene derivatives of barbituric acid and 2-thioxy-4-thiazolidone

1. By direct analysis of daughter ions, a study has been made of the paths of fragmentation of the molecular and fragment ions manifested in the mass spectra of arylidene derivatives of barbituric acid and 2-thioxy-4-thiazolidone. It has been shown that the fragmentation of these compounds proceeds through decomposition of the heterocyclic part and the substituents of the aryl part of the molecule. 2. It has been shown that the condensation of barbituric acid and 2-thioxy-4-thiazolidone with o-hydroxyaryl aldehydes proceeds with the formation of anomalous products, the structure of which has been established from an analysis of the spectral data.

Studies on hydantoin. Part 2. Substituent effects in 3-arylhydantoins on the formation of aryl isocyanate ions using the mass-analysed ion kinetic energy–direct analysis of daughter ions

The unimolecular reaction of seven 3-arylhydantoins, relatively slow fragmentation in the free drift region, has been investigated by analysis of the mass-analysed ion kinetic energy (m.i.k.e.) spectrum using direct analysis of daughter ions (d.a.d.i.). Aryl isocyanate ion formation, which gives the base peaks or highly abundant ions, occurs through three pathways involving initial loss of CO, CH, and C2H2NO, respectively, and the substituent effects on the competing metastable transitions have been found. For electron-attracting groups in the para- or meta-positions, loss of CO· is the dominant process. The formation of the M+˙– C2H2NO˙ ions is the major pathway for electron-donating groups in the aromatic ring. The substituent effects on the formation of aryl isocyanates obey the Hammett equation. Correlation with σ and σ+ are related semiquantitively to the solution chemistry of hydantoin.

Spectra of metastableions of positional isomers of methyl benzenepolycarboxylates

1. The method of direct analysis of daughter ions (DADI) has been used in studying 28 positional isomers of the methyl esters of phthalic and benzenetricarboxylic acids. 2. On the basis of the spectra obtained for the metastable ions M+, [M-OCH3 (or CH3OH)]+, and [M-COOCH3 (or HCOOCH3)]+, the isomers in question have been identified successfully. 3. In the DADI spectra of certain isomers, unusual high-intensity peaks with nonintegral values of m/z have been observed.

A study of complex mixtures of natural substances by the defocusing and DADI methods. III. Components of the protective secretion of the beetleCoccinella septempunctata

The composition of the protective secretion of the seven-spot ladybugCoccinella septempunctata L. (Coleoptera, Coccinellidae) has been studied by the methods of high- and low-resolution mass spectrometry. By determining the complete genetic link between the ions of a sample of the secretion by the methods of metastable defocussing and the direct analysis of daughter ions (DADI) the presence of the molecular ions of eight substances contained in the secretion has been shown. These components of the secretion have been identified as squalene, cholesterol, cholesta-3,5-diene, palmitic acid, and the alkaloids coccinellin, precoccinellin, and propylein, and a probable structure has been proposed for a base C13H16N.

Mass spectrometric study of sophoramine isomers by the direct analysis of daughter ions (DADI)

In a study of the mass spectra of sophoramine, isosophoramine, and neosophoramine by the direct analysis of daughter ions (DADI) it has been established that the ions with m/e 149 and 136 are formed from the molecular ions. Differences have been found in the DADI spectra of the alkaloids studied that are due to features of the three-dimensional structures of their molecules.

Mass spectra of substituted Δ2‐1,2,4‐oxadiazolines—I

AbstractThe electron impact fragmentation of four Δ2‐1,2,4‐oxadiazolines with substituents at positions 3 and 5 has been examined. The direct analysis of daughter ions and high resolution mass measurements provided valuable information regarding certain ions. The present study clearly demonstrates that the substitution of phenyl or a substituted phenyl group for alkyl at C‐3 and alkyl in place of a phenyl substituent at C‐5 in the oxadiazoline system alters the fragmentation modes considerably.

Massenspektroskopische untersuchungen an polyenantibiotika. Fragmentierungsverhalten einiger tetraene

Zusammenfassung By means of electron impact, electron attachment and DADI (direct analysis of daughter ions) mass spectroscopy the carbon skeletons of the aglycones of pimaricin, lucensomycin, tetrin A and B, rimocidin, and tetramycin have been determined using the original compounds. On the basis of these results the molecular weights of these polyene antibiotics have been derived. High resolution mass spectroscopy can be used effectively in the investigation on the structural arrangement of compounds related to these tetraene antibiotics.

Mass spectral studies on aminocyclitol–aminoglycoside antibiotics

The electron impact mass spectral fragmentation patterns of a series of underivatized aminocyclitol–aminoglycoside antibiotics are reported, and their utility in making structural assignments is discussed. The compositions of the fragment ions were confirmed by high resolution mass measurements, and in some cases the origins of the ions were determined by the “direct analysis of daughter ions” technique. The chemical ionization mass spectra of representative compounds of this class are also reported. In general the mass spectra of the underivatized compounds, at least up to the pseudotrisaccharide size, were simpler to interpret and afforded more useful diagnostic information than those of their more volatile permethyl, trimethylsilyl, and per-N-aralkylidene derivatives studied by others.

Detection of Fragment Genesis in the Mass Spectrometer: DADI Mass Spectrometry as an Aid in the Structure Analysis of Organic Compounds

Abstract“Direct Analysis of Daughter Ions” (DADI) can be carried out with commercial mass spectrometers embodying the Nier‐Johnson inverse geometry. DADI measurements permit experimental detection of the consecutive formation of molecule fragments (fragment genesis). Knowledge of fragment genesis enables the chemist to clarify the fragmentation processes of molecule‐ions and provides information on the structure of fragments formed in the mass spectrometer. In combination with classical mass spectrometry such information makes it easier to determine the structure of compounds, to analyze mixtures, to determine the sequence in periodically constructed molecules, for example oligopeptides, and to study rearrangement reactions occurring in the mass spectrometer.