Saturated Long-chain Hydrocarbons Research Articles

Structural investigations of Eocene coals from foreland basin of central Nepal Himalaya

Structural investigations of Eocene coal from foreland basin of central Nepal Himalaya were subjected to attenuated total reflection Fourier transform infrared spectroscopy, X-ray diffraction, high-resolution transmission electron microscopy and scanning electron microscopy to study their chemical and structural characteristics. The attenuated total reflection Fourier transform infrared spectroscopy data show that the less matured coal sample (sub-bituminous) has more aliphatic moieties, whereas the relatively more matured (bituminous) coal samples contain higher fractions of poly-aromatic moieties and saturated long-chain hydrocarbons. Fourier transform infrared spectroscopy spectra reveals the presence of stretching vibrations of aliphatic –CH, –CH2 and –CH3 absorptions, –OH bonds, C=C and –CH of aromatic structures and C=O stretching vibrations of carbonyl groups. X-ray diffraction indicates the presence of crystalline carbon having turbostratic structure along with some highly disordered amorphous car...

Synthesis and Characterization of Arsenolipids: Naturally Occurring Arsenic Compounds in Fish and Algae.

Arsenic-containing lipids (arsenolipids) are natural products present in fish and algae. Because these compounds occur in foods, there is considerable interest in their human toxicology. We report the synthesis and characterization of seven arsenic-containing lipids, including six natural products. The compounds comprise dimethylarsinyl groups attached to saturated long-chain hydrocarbons (three compounds), saturated long-chain fatty acids (two compounds), and monounsaturated long chain fatty acids (two compounds). The arsenic group was introduced through sodium dimethylarsenide or bis(dimethylarsenic) oxide. The latter route provided higher and more reproducible yields, and consequently, this pathway was followed to synthesize six of the seven compounds. Mass spectral properties are described to assist in the identification of these compounds in natural samples. The pure synthesized arsenolipids will be used for in vitro experiments with human cells to test their uptake, biotransformation, and possible toxic effects.

Structure and phase transitions of ultrathin films of alkanes adsorbed on Cu(111)

Monolayers of saturated long-chain hydrocarbons ( n-octane and n-nonane) were adsorbed on a Cu(111) surface and subsequently studied by high-resolution elastic and inelastic He-atom scattering as well as by low energy electron diffraction. At low surface temperatures (<160 K) the alkane-chains form ordered well-defined two-dimensional lattices. We find a herringbone structure with a p(5 3 ×2) unit cell for octane–Cu(111) and a domain wall lattice with a c( 3 ×11) unit cell for nonane–Cu(111). At elevated surface temperatures the systems undergo phase transitions to disordered, liquid-like states. Unexpectedly, the different structure observed for the nonane monolayer also results in a different type of phase transition. For nonane, an anomalously large Debye–Waller factor is observed, providing indirect evidence for the presence of low-energy excitations related to the presence of domain-walls.

The melting of a two-dimensional lattice of flexible rod-shaped molecules: structure and dynamics studied by He atom scattering

Monolayers of several saturated long-chain hydrocarbons (n-octane, perdeuterated n-octane, n-nonane and n-decane) adsorbed on a Cu(111) surface were studied by high-resolution elastic and inelastic He atom scattering. At low temperatures (<160 K) the alkane chains form an ordered, well-defined two-dimensional (2D) lattice with the molecular CCC planes being oriented parallel to the surface. At higher temperatures a phase transition to a disordered, liquid-like state with the transition temperature dependent on the length of the hydrocarbon chain is observed. These structural changes are accompanied by shifts of the frequencies of the external and internal vibrations of the adsorbed molecules, which indicate the presence of a large amount of conformational defects. In addition, the broadening of the quasielastic peak reveals a strong increase of the diffusion coefficient above the transition temperature.

Identification of transitions into Rydberg states in the X-ray absorption spectra of condensed long-chain alkanes

A detailed theoretical analysis of the high-resolution X-ray absorption spectra of condensed long-chain alkane molecules (hexatriacontane, C 36H 74 and heptatriacontane, C 37H 76) suggests that the resonance at 287.7 eV, which is the dominating feature in the near-edge X-ray absorption spectra of saturated long-chain hydrocarbons, is due to transitions into Rydberg states. These findings, which are at variance with the previous interpretation, are corroborated by the identification of a previously unresolved resonance at 288.2 eV in the high-resolution X-ray absorption spectra and of the observation of a strong quenching of the X-ray absorption resonances upon physisorption on a Cu(111)-metal surface.

Petroleum generation and migration in coal seams of the Carboniferous Ruhr Basin, northwest Germany

A series of 64 coal and clastic rock samples of Westphalian age was taken from five narrow (<3 m) depth intervals between 1200 and 1530 m depth and studied by geochemical and petrological methods. Maturity increases regularly with increasing depth as indicated by several maturity parameters. The influence of organic facies is evident in the uppermost coal seam (0.70% R r), where a hand-picked vitrinite contains less total extract and less saturated long-chain hydrocarbons than a directly adjacent sporinite-rich coal. Extracts from deeper and more mature coals are less affected by facies changes, probably due to enhanced petroleum redistribution in the seams. Total yield and gross composition of extracts in the deepest seam (0.92% R r) which is directly overlain by sandstone, seem to be influenced by the preferential expulsion of saturated hydrocarbons.

Aroma volatiles of Cynara scolymus and Helianthus tuberosus

Samples of the aroma volatiles of globe artichoke and Jerusalem artichoke were obtained by well established methods and were analysed by routine GC and GC/MS. Eight sesquiterpene hydrocarbons afforded the major group of components (over 42%) in globe artichoke samples, with β-selinene (ca 32%) as the main constituent. Previously reported caryophyllene could not be detected. α-Cedrene was found to have globe artichoke aroma characteristics on odour evaluation of separated components at an odour port at the exit of the GC column. Jerusalem artichoke samples contained one major component (β-bisabolene, ca 51%) and a range of saturated long-chain hydrocarbons (ca 22%). The sesquiterpene presumably contributes appreciably to the characteristic flavour of Jerusalem artichoke. Both types of artichoke gave a low concentration of total volatiles.

Aroma volatiles of Cynara scolymus and Helianthus tuberosus

Samples of the aroma volatiles of globe artichoke and Jerusalem artichoke were obtained by well established methods and were analysed by routine GC and GC/MS. Eight sesquiterpene hydrocarbons afforded the major group of components (over 42%) in globe artichoke samples, with β-selinene ( ca 32%) as the main constituent. Previously reported caryophyllene could not be detected. α-Cedrene was found to have globe artichoke aroma characteristics on odour evaluation of separated components at an odour port at the exit of the GC column. Jerusalem artichoke samples contained one major component (β-bisabolene, ca 51%) and a range of saturated long-chain hydrocarbons ( ca 22%). The sesquiterpene presumably contributes appreciably to the characteristic flavour of Jerusalem artichoke. Both types of artichoke gave a low concentration of total volatiles.