DADI Spectra Research Articles

Mass-spectrometric investigation of some new derivatives of the alkaloid lupinine

The mass spectra of some new derivatives of lupinine have been studied with the use of the spectra of metastable ions. On the basis of the results of an investigation of DADI spectra it has been shown that in the formation of low-mass quinolizidine ions the ions with m/z 152–150 are of considerable importance.

Mass spectrometric study of ring-substituted secondary and tertiary ?-aminopiperidines

Fragmentation of secondary and tertiary γ-aminopiperidines proceeds via elimination of γ-amino radicals and the ring substituents of piperidine, and is accompanied by their cleavage. High-resolution mass spectral data, DADI spectra, and fragmentation of deutero analogs confirm this decomposition. On the basis of quantum chemical MNDO calculations the most probable alternate structures have been proposed for a number of typical ions. From the features of dissociative ionization we can determine the kind and location of substituents in the piperidine ring.

Comparative study of mass-spectrometric behavior of 2,6-diaryl-4-(oxo,oximino,amino)piperidines

The fragmentation of the investigated piperidine derivatives, which was confirmed by data from the high-resolution spectra, by the DADI spectra, and by the fragmentation of the deutero analogs, proceeds with cleavage of the piperidine ring and is due to the competitive distribution of the charge on the ring nitrogen atom and on the structural elements that contain functional groups and an aryl radical. The dependence of the mass spectra of 4-(oxo,oximino,amino)piperidines on the nature and position of the substituents in the ring, as well as on the character of the functional group in the 4 position of the ring, was investigated.

Mass spectrometric study of 2-keto(thio)tetrahydropyrimidine derivatives

The fragmentation pathways of 2-keto(thio)-6-methyl-5-carbethoxy(acetyl)-4-aryl-1,2,3,4-tetrahydropyrimidines were established using high resolution mass spectra and DADI spectra. An unusual rearrangement was observed, which involves cyclization of the aryl substituent in the 4 position with the oxygen of an ester group and elimination of a C2H5 radical.

Mass spectra of piperidine dicarboxylic acids and their esters

Electron impact mass spectra of the epimers of 2,4-, 2,5-, and 2,6-piperidine dicarboxylic acids and their methyl esters and N-acyl derivatives have been studied. Data from DADI spectra have been used to establish the basic fragmentation paths. Chemical ionization spectra of positive and negative ions of 2,4- and 2,5-piperidine dicarboxylic acids are described.

ChemInform Abstract: MASS SPECTRA AND STRUCTURE OF IMINES OF 2‐AROYLBENZAMIDES

The electron impact mass spectra and DADI spectra of anils of N-alkyl-2-benzoylbenzamides and 2-alkyl-3-arylamino-3-phenylisoindolinones isomeric to them, as well as certain 2-substituted 3-alkyl(aryl)amino-3-phenylisoindolinones, were studied. The main direction of the decomposition were described. It was established that transition from 2-aroylbenzamides to their imines leads to a substantial stabilization of the cyclic isomeric form. A stabilization of the cyclic form with increasing steric volume of the alkyl substituent at the azomethine nitrogen atom was noted. The presence of a phenyl substituent at the nitrogen atom of the amide group destabilizes the cyclic form. A mechanism of isomerization explaining these phenomena is proposed.

Mass spectra and structure of imines of 2-aroylbenzamides

The electron impact mass spectra and DADI spectra of anils of N-alkyl-2-benzoylbenzamides and 2-alkyl-3-arylamino-3-phenylisoindolinones isomeric to them, as well as certain 2-substituted 3-alkyl(aryl)amino-3-phenylisoindolinones, were studied. The main direction of the decomposition were described. It was established that transition from 2-aroylbenzamides to their imines leads to a substantial stabilization of the cyclic isomeric form. A stabilization of the cyclic form with increasing steric volume of the alkyl substituent at the azomethine nitrogen atom was noted. The presence of a phenyl substituent at the nitrogen atom of the amide group destabilizes the cyclic form. A mechanism of isomerization explaining these phenomena is proposed.

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.

ChemInform Abstract: MASS SPECTRA AND STRUCTURE IN THE GAS PHASE OF ISOMERIC 2‐AROYLBENZAMIDES

The electron-impact mass spectra of various derivatives of 2-aroylbenzamides were studied. The principal pathways of fragmentation of the open and ring isomeric forms were described on the basis of an analysis of the high-resolution spectra and the DADI spectra. It is shown that peaks of ions formed in the fragmentation of the ring form, the intensities of which decrease as the volume of the substituent increases, are observed in the spectra of compounds with substituents R1 = H, CH3, and C2H5. Thermal isomerization of the ring form was proved on the basis of a study of the temperature effect on the intensities of the peaks of ions due to fragmentation of the open and ring forms when the samples are introduced through an inlet cylinder.

Mass spectra and structure in the gas phase of isomeric 2-aroylbenzamides

The electron-impact mass spectra of various derivatives of 2-aroylbenzamides were studied. The principal pathways of fragmentation of the open and ring isomeric forms were described on the basis of an analysis of the high-resolution spectra and the DADI spectra. It is shown that peaks of ions formed in the fragmentation of the ring form, the intensities of which decrease as the volume of the substituent increases, are observed in the spectra of compounds with substituents R1 = H, CH3, and C2H5. Thermal isomerization of the ring form was proved on the basis of a study of the temperature effect on the intensities of the peaks of ions due to fragmentation of the open and ring forms when the samples are introduced through an inlet cylinder.

?Interference? peaks in the DADI-MIKE spectra of methyl esters of benzenepolycarboxylic acids

1. The spectra of the metastable ions (DADI spectra) of 34 benzenepolycarboxylic acid methyl esters have been studied. 2. The DADI spectra contain intense peaks of the metastable ions I-1 and I-2 with nonintegral values of the mass numbers. 3. The appearance of the I-1 and I-2 peaks in the DADI spectra of the compounds investigated is explained by the superposition on the DADI spectrum (decomposition of ions in the second field-free region) of the spectrum of ions formed as a result of processes taking place in the first field-free region of the doublefocussing mass spectrometer.

The study of complex mixtures of natural substances by the defocusing and DADI methods. II. Phytosterols accompanying ?-sitosterol

Low- and high-resolution mass spectra and defocusing and DADI spectra of samples of β-sitosterol isolated from various plant material have been studied. The spectral information obtained has shown the presence in samples of β-sitosterol studied of minor accompanying components which have been identified as stigmasterol, campesterol, and cholesterol.

Dadi spectra of gossypol hexamethyl ethers and mixtures of them

The DADI spectra of the M+ ions of hexamethyl ethers of three tautomeric forms of gossypol and of mixtures of them have been studied. A specific fragmentation pathway of M+ for each form has been shown. On the basis of the results obtained, the amounts of the hexamethyl ethers of each tautomeric form produced in the methylation of gossypol have been found.

Study of nucleic acid bases by the DADI method

The DADI spectra of the nucleic acid bases adenine (I), guanine (II), Uracil (III), thymine (IV), cytosine (V), and 5-methylcytosine (VI) have been studied. It has been established that the samples of nucleic acid bases investigated are characterized by a specific pattern of the DADI spectra which reflects the nature of the molecular ion due to the structure of the given base and, in the case of M+ for (IV) and (VI) also the tautomeric state. The possibility has been shown of using the information obtained for the quantitative determination of (VI) in a mixture of bases.