Thermal isomerization of the isoxazole ring and rearrangement processes in the mass spectra of 3-aryl-5-methylisoxazole-4-carboxylic acids

1974 ◽  
Vol 10 (4) ◽  
pp. 397-399
Author(s):  
K. K. Zhigulev ◽  
R. A. Khmel'nitskii ◽  
M. A. Panina
Keyword(s):  
Carboxylic Acids ◽  
Mass Spectra ◽  
Thermal Isomerization ◽  
Isoxazole Ring ◽  
Rearrangement Processes

Rearrangement processes and stability of molecular ions in the mass spectra of 3-aryl-5-methylisoxazole-4-carboxylic acids

1972 ◽  
Vol 8 (7) ◽  
pp. 806-809
Author(s):  
K. K. Zhigulev ◽  
R. A. Khmel 'nitskii ◽  
M. A. Panina ◽  
I. I. Grandberg ◽  
B. M. Zolotarev
Keyword(s):  
Carboxylic Acids ◽  
Mass Spectra ◽  
Molecular Ions ◽  
Rearrangement Processes

Electron impact studies. XXXVII. Skeletal-rearrangement fragments in the mass spectra of alkyl and aryl isoxazoles

1969 ◽  
Vol 22 (3) ◽  
pp. 563 ◽  
Author(s):  
JH Bowie ◽  
RKMR Kallury ◽  
RG Cooks
Keyword(s):  
Electron Impact ◽  
Mass Spectra ◽  
Skeletal Rearrangement ◽  
Deuterium Labelling ◽  
Isoxazole Ring ◽  
Impact Studies ◽  
Rearrangement Processes

The mass spectra of substituted isoxazoles are reported and discussed. The spectra of isoxazoles are strikingly different from those of oxazoles because the initial fragmentations of isoxazoles involve N-O bond fission. Specific skeletal-rearrangement processes are observed in many spectra, and it is proposed that they proceed through azirine and oxazole intermediates. Certain fragmentations have been studied by deuterium labelling. The hydrogens attached to an isoxazole ring do not randomize with the hydrogens of the methyl and phenyl substituents.

scholarly journals Intracrystalline biomolecules in Recent and fossil brachiopod shells - the biochemistry of shell coloration

1992 ◽  
Vol 6 ◽  
pp. 59-59
Author(s):  
Heather Clegg ◽  
Gordon B. Curry
Keyword(s):  
Gas Chromatography ◽  
Carboxylic Acids ◽  
High Performance ◽  
Mass Spectra ◽  
Organic Molecules ◽  
Degradation Products ◽  
Polyacrylamide Gel Electrophoresis ◽  
Reference Points ◽  
Gas Chromatography Mass Spectrometry ◽  
Magnesium Calcite

The study of fossil biomolecules requires not only well preserved fossil samples, but abundant Recent material so that reference points can be established. Ideally it would also be possible to study the in situ decay of organic molecules in samples of different geological ages, and hence determine how degradation proceeds with time. The shells of brachiopods fulfill both these criteria, containing up to 1% organic components entombed within their shells, which are composed of highly stable, low magnesium calcite, that survives well in the fossil record for hundreds of millions of years.This particular study has concentrated on Plio-Pleistocene brachiopods from New Zealand. These fossils are the ancestors of living species, and hence it is possible to investigate intracrystalline biomolecules in modern day shells, as well as the degradation products of such biomolecules in fossil shells of the same species.Three of the species investigated have bright red shells in life, and during the study it became clear that this coloration was caused by a carotenoprotein which was embedded within, rather than around, the calcite fibres of the brachiopod shell. Carotenoproteins are composite molecules composed of a protein and a prosthetic carotenoid group. The protein has been characterised by hplc (high performance liquid chromatography) and SDS PAGE (sodium dodecylsulphate polyacrylamide gel electrophoresis), and the amino acids at the N-termini have been sequenced, demonstrating that this is a small protein which has a molecular weight of 6.5 kDa and is identical in all 3 species.At least two different types of carotenoids were detected after initial purification, and these were characterised using direct probe mass spectra, and hplc/mass spectra. Using these techniques the two carotenoids have been tentatively identified as canthaxanthin and the mono acetylenic analogue of asthaxanthin.In addition to the carotenoproteins, the calcite crystals of recent brachiopod shells contain lipids (carboxylic acids) and carbohydrates, which were characterised by gas chromatography (GC) and gas chromatography/mass spectrometry analyses (GC/MS).Fossil brachiopod shells could be distinguished from recent shells due to their lack of unsaturated acids and smaller amounts of carboxylic acids present. However there was no trend of decreasing quantities of fatty acid with increasing age.The presence of organic molecules such as carotenoproteins, lipids and carbohydrates within calcite crystals poses two questions. Firstly, are these compounds merely wastes metabolic products and are deposited within the shell during growth or, secondly, do they play an important role in the process of biomineralisation? At present these questions remain largely unanswered, because at present only the function of the carotenoprotein has been determined from the spectrum of biomolecules present within the shell (and the carotenoprotein may have other functions apart from coloration).

scholarly journals 4-t-Butylbenzylation of carboxylic acid for GC–MS analysis

2020 ◽  
Vol 2 (5) ◽  
Author(s):  
Shinji Tsunoi ◽  
Nao Yamamoto ◽  
Tomohiro Yasuhisa ◽  
Riko Akehi ◽  
Itaru Suzuki ◽  
...  
Keyword(s):  
Carboxylic Acid ◽  
Carboxylic Acids ◽  
Water Samples ◽  
Mass Spectra ◽  
Molecular Ions ◽  
Good Sensitivity ◽  
Good Reproducibility ◽  
Methyl Radical ◽  
Microwave Reactor

Abstract We report a 4-t-butylbenzyl derivatization for the analysis of carboxylic acids by GC–MS (EI). Carboxylic acids were analyzed as a 4-t-butylbenzyl ester after the derivatization with 4-t-butylbenzyl bromide. On the mass spectra of 4-t-butylbenzyl ester, [M-15]+ ions were observed with high intensity. These ions were tertiary benzyl cations generated by the elimination of a methyl radical from molecular ions. After optimization of the 4-t-butylbenzyl derivatization conditions using microwave reactor, we established a method for the determination of the carboxylic acids in water samples. The method showed good sensitivity and good reproducibility, and was successfully applied to the analysis of rain water samples.

Chemical Compounds from Femoral Gland Secretions of Male Iberian Rock Lizards, Lacerta monticola cyreni

2005 ◽  
Vol 60 (7-8) ◽  
pp. 632-636 ◽  
Author(s):  
Pilar López ◽  
José Martín
Keyword(s):  
Carboxylic Acids ◽  
Mass Spectra ◽  
Scent Marking ◽  
Health Condition ◽  
Lizard Species ◽  
Lipophilic Compounds ◽  
Esters Of Carboxylic Acids ◽  
The Social ◽  
High Interindividual Variability ◽  
Femoral Gland Secretions

In spite of the importance of chemoreception and chemical signals in the social organization of lizards, there are only a few studies examining the chemical composition of secretions of lizards used for scent marking. The secretion of the femoral glands of male Iberian rock lizards (Lacerta monticola cyreni) contains 44 lipophilic compounds, including several steroids (mainly cholesterol), and n-C6 to n-C22 carboxylic acids, and minor components such as esters of carboxylic acids, alcohols, squalene, and one lactone. These compounds were identified on the basis of mass spectra, obtained by GC-MS. Most lipids were detected in all individuals, although relative proportions of each chemical show a high interindividual variability. This variability might be related to the characteristics or physical and health condition of males and might be the basis of female choice based on chemical cues observed in this lizard species.

Fragmentation and rearrangement processes in the mass spectra of perfluoroaromatic compounds. Part XI. Heterocyclic derivatives of phosphorus and some transition metals

1979 ◽  
Vol 57 (3) ◽  
pp. 335-341 ◽  
Author(s):  
Timothy R. B. Jones ◽  
Jack M. Miller ◽  
Sylvia A. Gardner ◽  
Marvin D. Rausch
Keyword(s):  
Transition Metals ◽  
Special Interest ◽  
Mass Spectra ◽  
Central Atom ◽  
General Structure ◽  
Heterocyclic Derivatives ◽  
Derivatives Of ◽  
Rearrangement Processes

The mass spectra of a number of phospholes and metalloles of general structure 1 and 2 are[Formula: see text]discussed with respect to their fragmentation and ion rearrangement processes. Of special interest is the migration of ring fluorines to the central atom during fragmentation. The bonding principles involved for the postulated intermediates are discussed.

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