The behaviour of stereoisomeric ions in the gas phase: 2—Negative and positive chemical ionization of cyclohexanehexacarboxylic methyl esters

The positive ion chemical ionization (CI (isobutane)), negative ion chemical ionization (NICI) electron attachment (CH₄, He) and NICI (OH^?) spectra of the title compounds have been studied in detail with the aid of deuterium-labelled derivatives. The obtained results show that under CI conditions the stereospecificity is retained. Interesting correlations with the condensed phase epimerization yields are emphasized.     

Complete 1H and 13C NMR assignments of aurasperone A and fonsecinone A, two bis-naphthopyrones produced by Aspergillus aculeatus

Complete assignments of 1H and 13C NMR chemical shifts of the polyketides aurasperone A and fonsecinone A were made by means of nuclear Overhauser enhancement and heteronuclear NMR correlation experiments. These compounds were isolated for the first time from Aspergillus aculeatus, an endophytic fungus obtained from leaves of Melia azedarach(Meliaceae).     

3-methylthiophene self-assembled monolayers on planar and nanoparticle Au surfaces

In this article the adsorption of 3-methylthiophene on planar and nanoparticle Au surfaces is investigated. The resulting systems are compared with a benchmark system based on 1-decanethiol. The characterization data collected evidence the formation of a packed 3-methylthiophene SAM on the planar surface. In particular, spectroscopic investigations suggest that 3-methylthiophene aromatic system is not adsorbed on the surface through the pi-electron system but rather through the S atom alone. On the other hand, the behavior of 3-methylthiophene on nanoparticle surfaces is notably different from that of the alkanethiol. Only a limited fraction of the surface of Au nanoparticles results to be actually coated after purification; this notwithstanding, the nanoparticle growth seems to be strongly influenced by the presence of such a labile encapsulating agent.     

Secondary ion mass spectrometric investigation of Au-based composites.

The electrodeposition of thick gold layers plays an important role both in traditional and high-tech productions, such as jewelry and microelectronics, respectively. In this work a secondary ion mass spectrometric study will be presented on Au co-deposits with (sub-)micrometric ceramic powders, in order to harden gold. Mass spectra are used to identify the components deposited, providing evidence of the additives and/or eventual contaminants introduced during electrolysis. Furthermore, analysis of ion depth profiles and the intensity distribution of ionic species along the film were studied.     

Gas chromatographic/mass spectrometric identification of some organic compounds and odours in poultry wastes

Air and waste samples coming from poultry breeding farms have been analysed by means of thermal desorption coupled to the gas chromatographic/mass spectrometric technique. The solid samples not only showed the presence of organic compounds such as acids, sulphides, benzopyrroles and phenols originated by anaerobic biotransfor-mation of the natural products, but also the occurrence of anti-oxidant substances: 2,6-di-tert-butylcresol, 2,6-di-tert-butylphenol and two of their oxidation derivatives. In the air, four artificial benzoquinones were detected, two of which had already been identified in the solid waste. In this work, the mechanism by which oxidized compounds are formed, is suggested.     

A mass spectrometric study of the adducts of acetylacetone and cyanogen (Traube's isomers)

The mass spectrometric behaviour of the title compounds has been studied in detail with the aid of deuterium labelling, exact mass measurements, linked scans and collisionally activated decomposition experiments. An interesting conversion reaction of the cyanoenaminedione isomer into the corresponding furane derivative, which appears complete in the second field free region, has been thoroughly investigated.     

The Relevance of Size Matching in Self-assembly: Impact on Regio- and Chemoselective Cocrystallizations

Decamethonium diiodide is reported to perform the chemo- and regioselective encapsulation of para-dihalobenzenes through the competitive formation of halogen-bonded cocrystals starting from solutions that also contain ortho and meta isomers. Selective caging in the solid occurs even when an excess ortho or meta isomers, or even a mixture of them, is present in the solution. A prime matching between the size and shape of the dication and the formed dianions plays a key role in enabling the selective self-assembly, as proven by successful encapsulation of halogen-bond donors as weak as 1,4-dichlorobenzene and by the results of cocrystallization trials involving mismatching tectons. Encapsulated para-dihalobenzenes guest molecules can be removed quantitatively by heating the cocrystals under reduced pressure and be recovered as pure materials. The residual decamethonium diiodide can be recycled with no reduction in selectivity.     

Electron impact mass spectrometry of some 2,3-dihydro-1-benzofuran-3-acetic acids

The mass spectrometric behaviour of four 2,3-dihydro-1-benzofuran-3-acetic acids has been studied in detail with the aid of exact mass measurements, linked scans, collisionally activated decomposition, mass analysed ion kinetic energy spectra and labelling experiments. Unusual fragmentation pathways are emphasized for which mechanisms are proposed.     

Mass spectrometric studies on cyclo- and poly-phosphazenes: 4—Attempts at mass spectrometrically induced polymerization of cyclotriphosphazenes substituted with primary and secondary amines

In this paper, the mass spectrometric behaviour of cyclophosphazenes substituted with primary and secondary amines is investigated, together with the mass spectrometric polymerization pattern of these compounds. While it is not possible to achieve the mass spectrometric polymerization of hexa(anilino)cyclotriphosphazene, ion–molecule reactions take place in the case of hexa(piperidino)- and hexa(morpholino)cyclotriphosphazenes, which lead to the formation of hexameric species. Evidence is given that pentasubstituted cyclophosphazenephosphorus cations are the species responsible for the oligomerization process.