Alkali-metal salts of aromatic carboxylic acids: Liquid crystals without flexible chains

The alkali-metal salts of meta-substituted benzoic acids exhibit a smectic A mesophase at high temperatures. These compounds are examples of liquid crystals without terminal alkyl chains. The influence of the metal ion and of the type of substituents on the transition temperatures is discussed. Compounds with the substituent in the ortho- and para-positions are non-mesomorphic. The crystal structures of the compounds Rb(C7H4ClO2)(C7H4ClO2H), Na(C7H4IO2)(H2O), K(C7H4ClO2)(C7H4ClO2H) and Rb(C7H4BrO2)(C7H4BrO2H) have been determined by X-ray crystallography. These compounds possess a layerlike structure in the solid state. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Remote chiral induction in the organocatalytic hydrosilylation of aromatic ketones and ketimines

Lewis basic, metal-free pyridyloxazolines catalyze the redn. of prochiral arom. ketones and ketimines with Cl3SiH in good enantioselectivity (? 94% ee). Arene-arene interactions between the substrate and the catalyst are likely to play a role in the enantiodifferentiation process.

Chemoenzymatic Synthesis of Carbasugars (+)-Pericosines A-C from Diverse Aromatic cis-Dihydrodiol Precursors

cis-Dihydrocatechols, derived from biological cis-dihydroxylation of methyl benzoate, iodobenzene and benzonitrile, using the microorganism Pseudomonas putida UV4, were converted into pericosines A, C, and B, respectively. This approach constitutes the shortest syntheses, to date, of these important natural products with densely packed functionalities.

Assembly of a coordination cage with four aromatic channel receptors on the outside

Silver salts and triphosphine ligands with biphenyl substituents assemble to give coordination cages with four external aromatic channel receptors in a pseudo-tetrahedral arrangement.

1-Ethyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}amide as solvent for the separation of aromatic and aliphatic hydrocarbons by liquid extraction - extension to C-7- and C-8-fractions

The ionic liquid 1-ethyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}amide ([C(2)mim][NTf2]) was tested as solvent for the separation of aromatic and aliphatic hydrocarbons containing 7 or 8 carbon atoms (the C-7- and C-8-fractions). The liquid-liquid equilibria (LLE) of the ternary systems (heptane + toluene + [C(2)mim][NTf2]) and (octane + ethylbenzene + [C(2)mim][NTf2]), at 25 degrees C, were experimentally determined. The performance of the ionic liquid as the solvent in such systems was evaluated by means of the calculation of the solute distribution ratio and the selectivity. The results were compared to those previously reported for the extraction of benzene from its mixtures with hexane by using the same ionic liquid, therefore analysing the influence of the size of the hydrocarbons. It was found that the ionic liquid is also good for the extraction of C-7- and C-8- fraction aromatic compounds, just a greater amount of ionic liquid being needed to perform an equivalently efficient separation than for the C-6-fraction. It is also discussed how [C(2)mim][NTf2] performs comparably better than the conventional solvent sulfolane. The original 'Non-Random Two-Liquid' (NRTL) equation was used to adequately correlate the experimental LLE data.

Contrasting effects of a nonionic surfactant on the biotransformation of polycyclic aromatic hydrocarbons to cis-dihydrodiols by soil bacteria

The biotransformation of the polycyclic aromatic hydrocarbons (PAHs) naphthalene and phenanthrene was investigated by using two dioxygenase-expressing bacteria, Pseudomonas sp. strain 9816/11 and Sphingomonas yanoikuyae B8/36, under conditions which facilitate mass-transfer limited substrate oxidation. Both of these strains are mutants that accumulate cis-dihydrodiol metabolites under the reaction conditions used. The effects of the nonpolar solvent 2,2,4,4,6,8,8-heptamethylnonane (HMN) and the nonionic surfactant Triton X-100 on the rate of accumulation of these metabolites were determined. HMN increased the rate of accumulation of metabolites for both microorganisms, with both substrates. The enhancement effect was most noticeable with phenanthrene, which has a lower aqueous solubility than naphthalene. Triton X-100 increased the rate of oxidation of the PAHs with strain 9816/11 with the effect being most noticeable when phenanthrene was used as a substrate. However, the surfactant inhibited the biotransformation of both naphthalene and phenanthrene with strain B8/36 under the same conditions. The observation that a nonionic surfactant could have such contrasting effects on PAH oxidation by different bacteria, which are known to be important for the degradation of these compounds in the environment, may explain why previous research on the application of the surfactants to PAH bioremediation has yielded inconclusive results. The surfactant inhibited growth of the wild-type strain S. yanoikuyae B1 on aromatic compounds but did not inhibit B8/36 dioxygenase enzyme activity in vitro.

Thin-film oxygen sensors using a luminescent polynuclear gold(I) complex

Robust thin-film oxygen sensors were fabricated by encapsulating a lipophilic, polynuclear gold(I) complex, bis{m-(bis(diphenylphosphino)octadecylamine-P,P')}dichlorodigold(I), in oxygen permeable polystyrene and ormosil matrices. Strong phosphorescence, which was quenched by gaseous and dissolved oxygen, was observed from both matrices. The polystyrene encapsulated dye exhibited downward-turning Stern-Volmer plots which were well fitted by a two-site model. The ormosil trapped complex showed linear Stern-Volmer plots for dissolved oxygen quenching but was downward turning for gaseous oxygen. No leaching was observed when the ormosil based sensors were immersed in flowing water over an 8 h period. Both films exhibited fully reversible response and recovery to changing oxygen concentration with rapid response times. (C) 2011 Elsevier B.V. All rights reserved.

Polycyclic aromatic hydrocarbon (PAH) dispersion and deposition to vegetation and soil following a large scale chemical fire

Polycyclic aromatic hydrocarbons (PAHs) were determined in soil and vegetation following a large scale chemical fire involving 10,000 ton of polypropylene. In comparison with sites outside the plume from the fire, PAH concentrations were elevated in grass shoots (by up to 70-fold) and in soil (by up to 370-fold). The pattern of PAH dispersion under the plume was dependent on the physical-chemical properties of individual PAHs. The lighter, least hydrophobic PAHs were dispersed into the environment at greater distances than heavier, more hydrophobic PAHs. At the most distant sampling point (4.5 km) under the plume, the low molecular weight PAHs were still considerably elevated in vegetation samples compared to control sites. Dispersion appeared to be regulated by the compounds partitioning between the vapour and particulate phase, with dry particulate deposition occurring closer to the fire source than gaseous deposition. For all PAHs, the fire resulted in greater contamination of soils compared to grasses, with the relative ratio of plant/soil contamination decreasing as hydrophobicity increased.

Phase I and II biotransformation enzymes and polycyclic aromatic hydrocarbons in the Mediterranean mussel (Mytilus galloprovincialis, Lamarck, 1819) collected in front of an oil refinery

The aim of the present study was to investigate the responses of phase I and II biotransformation enzymes and levels of PAHs in the Mediterranean mussel (Mytilus galloprovincialis, Lamarck, 1819) collected from three sites at different distance from an oil refinery. Phase I enzyme activities as NAD(P)H-cyt c red, NADH ferry red, B(a)PMO and phase II as UDPGT. GST were measured in digestive gland while 16 PAHs (US-EPA) in whole soft tissue. An added value to the data obtained in the present study rely on the RDA analysis which showed close correlations between PAHs levels and phase I enzyme activities in mussels collected in front of the refinery. And again a significant spatial correlation between B(a)P levels and NADPH-cyt c red activities was observed using linear models. No differences among sites for B(a) PMO and phase II GST activities were observed, while the application of UDPGT as biomarkers requires further investigation. (C) 2012 Elsevier Ltd. All rights reserved.

Optimised extraction of heterocyclic aromatic amines from blood using hollow fibre membrane liquid-phase microextraction and triple quadrupole mass spectrometry

Heterocyclic aromatic amines (HCA) are carcinogenic mutagens formed during cooking of proteinaceous foods, particularly meat. To assist in the ongoing search for biomarkers of HCA exposure in blood, a method is described for the extraction from human plasma of the most abundant HCAs: 2-Amino-1-methyl-6-phenylimidazo(4,5-b)pyridine (PhIP), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (4,8-DiMeIQx) (and its isomer 7,8-DiMeIQx), using Hollow Fibre Membrane Liquid-Phase Microextraction. This technique employs 2.5 cm lengths of porous polypropylene fibres impregnated with organic solvent to facilitate simultaneous extraction from an alkaline aqueous sample into a low volume acidic acceptor phase. This low cost protocol is extensively optimised for fibre length, extraction time, sample pH and volume. Detection is by UPLC-MS/MS using positive mode electrospray ionisation with a 3.4 min runtime, with optimum peak shape, sensitivity and baseline separation being achieved at pH 9.5. To our knowledge this is the first description of HCA chromatography under alkaline conditions. Application of fixed ion ratio tolerances for confirmation of analyte identity is discussed. Assay precision is between 4.5 and 8.8% while lower limits of detection between 2 and 5 pg/mL are below the concentrations postulated for acid-labile HCA-protein adducts in blood.