Oxygen heterocycles, mass spectrometry

A number of review articles deal with electron impact mass spectra of oxygen heterocycles (69BSF4545, B-71MS139, B-74MI22202), but little use appears to have been made of techniques such as chemical ionization or negative ion spectrometry. 

P. Dugo, L. Mondello, E. Sebastiani, R. Ottana, G. Errante and G. Dugo, Identification of minor oxygen heterocyclic compounds of citrus essential oils by hquid chromatography-atmospheric pressure chemical ionisation mass spectrometry , J. Fiq. Chromatogr. 22 2991-3005(1999). 

Ion cyclotron double resonance has been usefully applied by the authors [1415] for structural identification of isomeric ions with m/z 152 obtained under electron impact of both l-methyl-4-nitro-5-caronitrylimidazole and l-methyl-4-nitro-5-caroxamidimidazole. The ion cyclotron resonance and mass spectrometry data show that the protonation 3- and 4-nitropyrazole proceeds on the heterocyclic nitrogen rather than on the oxygen of the nitro group [1416],... 

Mass spectral techniques in heterocyclic chemistry applications and stereochemical considerations in carbohydrates and other oxygen heterocycles, 42, 335 Mass spectrometry of heterocyclic compunds, 7, 301 of nucleic acids, 39, 79 Medium-large and large 7r-excessive heteroannulenes, 23, 55 Meso-ionic compounds, 19, 1 Metal catalysts, action on pyridines, 2, 179 Metalation, directed, of pyridines, quinolines, and diazines, 52, 187... 

The amount of information available on stereochemical effects in mass spectrometry is very large. Compiling this article, however, highlighted the need for more thorough studies on given families of oxygen heterocycles. The few scattered data published to date warrant this closer examination. Carbohydrates seem to be the exception to this statement, due largely to their broad use in various applications. 

The oxygen heterocyclic compounds present in the nonvolatile residue of citrus essential oils have also been extensively investigated by means of HPLC-atmospheric pressure ionization-mass spectrometry (HPLC-API-MS) [99]. The mass spectra obtained at different voltages of the sample cone have been used to build a library. Citrus essential oils have been analyzed with this system, using an optimized NP-HPLC method, and the mass spectra were compared with those of the laboratory-constructed library. This approach allowed the rapid identi cation and characterization of oxygen heterocyclic compounds of citrus oils, the detection of some minor components for the rst time in some oils, and also the detection of authenticity and possible adulteration. 

Spectrometrie de Masse des Heterocycles Oxygenes C. Mercier, Bull. Soc. Chim. Fr., 1969, 4545-4560. 

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