Mass-spectral methods for the detection and identification of organic tautomers in the gas phase are reviewed together with the thermochemical and quantum chemical evidence for the stability of the respective tautomeric forms in the gas phase. The literature (approximately 150 references) is covered to 1995. © 1997 John Wiley & Sons, Inc., Mass Spectrom Rev 15(6), 339-363, 1997.

Application of mass spectrometry for the analysis of organic tautomeric compounds.

Investigation of diazepam drug using thermal analyses, mass spectrometry and semi-empirical MO calculation

Six stable isomers andtwo transition structures were characterized on the C3H4O+˙ potential energy surface using the G2 procedure. Heat capacity corrections were made to allow the direct calculation of heats of formation at 298 K. The most stable isomer is the methylketene radical cation (1, ΔHf 298 = 797.0 kJ mol−1), followed by a distonic ion (2), only 46.5 kJ Mol−1 higher in energy (ΔHf 298 = 843.5 kJ mol−1). Ionized cyclopropanone (7) represents a transition structure for exchange of terminal methylene groups in the distonic ion with a corresponding barrier of 57.6 kJ mol−1. There is amuch larger barrier (106.7 kJ mol−1) for the 1,2-hydrogen migration in the distonic ion (2) to form the mor estabe ionized methylketene (I), while the fragmentation of 2 to C2H4+˙ + CO is highlyendothermic (by 113.1 kJ mol−1). The predicted ease of formation of the distonic ion on ionization of neutral cyclopropanone (7n) and the higher barrier for further reaction would suggest that ionized cyclopropanone should show reactivity characteristic of a radical as observed for ionized cyclobutanone. Three additional C3H4O+˙ isomers, hydroxyallene radical cation (3), acrolein radical cation (4) and oxetene radical cation (5), lie within 15 kJ mol−1 of one another in energy, while a cyclic form (6) of the distonic ion is much less stable. G2 heats of formation and adiabatic ionization energies were also calculated for four of the neutral C3H4O analogs. WHile the ionization energies are in good agreement with available experimental values, as are the heats of formation for acrolein (4n) and cyclopropanone (7n), the G2 heat of formation of methylketene (−65.1 ± 10 kJ mol−1) is almost 40 kJ mol−1 higher than the ‘standard’ value, which it is considered shoul dbe revised. Calculations iwth the G2(MP2) method, which is less computationally intensive than G2, yields of formation for the neutral and ionic species within 24 kJ mol−1 of the G2 values.

Structures and stabilities of C3H4O+˙ isomers: A G2 theoretical study

Mass spectrometric investigation of buspirone drug in comparison with thermal analyses and MO-calculations.

https://link.springer.com/content/pdf/10.1016/1044-0305(93)85064-5.pdf

Functional group-selective ion-molecule reactions of ethylene glycol and its monomethyl and dimethyl ethers

A semiempirical MNDO method was used in calculations on monosubstituted neutral and cationic compounds of the [CH 3 −CO−R] type with a wide range of substituents (R=H, F, Cl, CH 3 , NH 2 , OH, OCH 3 , NHCH 3 , CH=CH 2 ). The results obtained are interpreted with respect to the effect of the individual substituents on the geometry and electron distribution in the systems studied and allow the conclusion that the ratios of partial charges in the individual substructures in a radical cation correspond to those of the respective peak intensities in the mass spectrum

Mndo study of fragmentations in mass spectrometry. Part II. Substituent effects in the ioinization of [CH3COR] compounds and their enol tautomers

MNDO calculations of [C 3 H 6O] +. predict the parallel existence of both structures of radical cations of acetone (1) and propen-2-ol (2) in electron ionization spectra. The calculated heats of formation of 1 +. (△H f MNDO =783.2 kJ mol −1 and of 2 +. (△H f MNDO =649.8 kJ mol −1 ) are in very good agreement with the experimental results. A comparison with the results of ab initio calculations (3-21G and &-#!G) and experimental data for the individual structures of the main fragment [C 2H3O] + demonstrates a sufficient accuracy of MNDO results, suggesting the possibility of applying the method also in other cationic systems, especially in larger ones

MNDO study of fragmentations in mass spectrometry. Part I. The geometry and electron structure of [C3H6O] + ˙ systems and [C2H3O]+ ions

A technical dye of the anthraquinone type was analyzed by GPC, mass spectroscopy, and elemental analysis. Along with the polymerizable component, N-[4-amino-3-methoxyanthraquinonyl-(1)] methacrylamide (I), it contained a saturated admixture, N-[4-amino-3-methoxyanthraquinonyl-(1)]-2-chloro-2-methylpropionamide (II). The homopolymerization of I was carried out, and admixture II was isolated and characterized. The copolymerization of the dye with styrene and methyl methacrylate was verified, and the retardation effect of II on the polymerization of these monomers was evaluated.



Ein technischer Anthrachinonfarbstoff wurde durch GPC, Massenspektroskopie und Elementaranalyse charakterisiert. Neben der polymerisierbaren Komponente, N-[4-Amino-3-methoxy-anthrachinonyl-(1)]methacrylsaureamid (I), enthielt er eine gesattigte Beimischung, N-[4-Amino-3-methoxy-anthrachinonyl-(1)]-2-chlor-2-methylpropionsaureamid (II). Es wurde die Homopolymerisation von I und die Isolierung und Charakterisierung der Beimischung II durchgefuhrt. Die Copolymerisation des Farbstoffs mit Styrol und Methylmethacrylat wurde untersucht, und der Verzogerungseffekt von II auf die Polymerisation dieser Monomeren wurde abgeschatzt.

Polymerization characteristics of a dye of anthraquinone

MNDO calculations on compounds CH3R (where R H, F, Cl, OH, SH, NH2) enable qualitative correlations to be made between the changes in bond length during ionization and the observed fragmentation of the ion formed. The relatively simple, semi-empirical MNDO method gives data adequate for the calculation of the geometries and energies involved.

An MNDO study of substituent effects on the electronic structure and geometry in the ionization of CH3R compounds (R = H, F, Cl, OH, SH, NH2)

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Mndo study of fragmentations in mass spectrometry. Part II. Substituent effects in the ioinization of [CH3COR] compounds and their enol tautomers

MNDO study of fragmentations in mass spectrometry. Part I. The geometry and electron structure of [C3H6O] + ˙ systems and [C2H3O]+ ions

Polymerization characteristics of a dye of anthraquinone

An MNDO study of substituent effects on the electronic structure and geometry in the ionization of CH3R compounds (R = H, F, Cl, OH, SH, NH2)