Abstract  One-dimensional and comprehensive two-dimensional flow modulated gas chromatography with simultaneous flame ionization and mass spectrometric detection were applied for the identification and quantification of benzene, toluene, ethyl benzene and xylenes (BTEX) as well as of all C9-C11 aromatic hydrocarbons in the low-boiling petroleum products gasoline, reformate and fluid catalytic cracking (FCC) samples. GC x GC experiments were performed on two reversed phase polarity column sets namely SLB-IL100 (25 m x 250 mu m i.d. x 0.2 mu m d(f)) + HP-5MS (5 m x 250 mu m i.d. x 0.25 mu m d(f)) and SLB-IL111 (30 m x 250 mu m i.d. x 0.2 mu m d(f))+ HP-5MS (5 m x 250 mu m id. x 0.25 pm d(f)). The one-dimensional GC experiments were carried out on the same ionic liquid columns. The most powerful method is GC x GC on the SLB-111+ HP-5MS column combination. Quantitative analysis of individual aromatic hydrocarbons (C6-C11) present in gasoline, reformate and fluid catalytic cracking (FCC) samples was performed by GC x GC-FID using the internal normalization method. Mass spectra obtained by GC x GC-qMSD were used for identification of the aromatic hydrocarbons in these samples. (C) 2013 Elsevier B.V. All rights reserved.

Abstract  The structure of gaseous counterflow diffusion flames perturbed with the addition of hundreds of ppm of prevaporized 1,2,4-trimethyl benzene (TMB) is studied in two distinct flame environments: a blue methane flame and an incipiently sooting ethylene flame. The two flames provide well defined temperature-time histories and chemical environments to investigate the behavior of complex fuels and complement other reacting environments lacking the coupling of kinetics and transport that is typical of flame environments. Profiles of critical pyrolysis products and of some stable soot precursors are determined from GC/MS analysis of gas samples extracted from the flames and compared with results from the OPPDIFF model using a semi-detailed chemical mechanism. Experimentally, because of the presence of aliphatic fragments, TMB reactivity is enhanced in these flames with the onset of TMB decay beginning at relatively modest temperatures, on the order of 800 K. The dominant path to stable species is driven by H radical attack. It leads in sequence to xylenes, toluene (through benzyl radical) and benzene formation. This enhanced reactivity is captured reasonably well by the model in the methane flame, but not in the ethylene flame, in the presence of a richer, more complex mixture. The model does not reproduce accurately the pathway yielding C3 and some C4 species from TMB cracking. Aromatic ring opening is the bottleneck in the TMB cracking process in the methane flame but not in the ethylene one. Indene, an important soot precursor for monoaromatic fuels since the second aromatic ring formation is considered to be a bottleneck in the process, is measured in the ethylene flame in poor agreement with the model predictions. The dataset presented here and available supplemental data online may help identifying improvements to the chemical kinetic mechanism of this reference fuel. (c) 2012 Published by Elsevier Inc. on behalf of The Combustion Institute.

Abstract  Certain coral reef systems north of the Arabian Gulf are characterized by corals with a unique ability to thrive and flourish despite the presence of crude oil continuously seeping from natural cracks in the seabed. Harboring oil-degrading bacteria as a part of the holobiont has been investigated as a potential mechanism of adaptation and survival for corals in such systems. The use of conventional and molecular techniques verified a predominance of bacteria affiliated with Gammaproteobacteria, Actinobacteria and Firmicutes in the mucus and tissues of Acropora clathrata and Porites compressa. These bacteria were capable of degrading a wide range of aliphatic (C9-C28) aromatic hydrocarbons (Phenanthrene, Biphenyl, Naphthalene) and crude oil. In addition, microcosms supplied with coral samples and various concentrations of crude oil shifted their bacterial population toward the more advantageous types of oil degraders as oil concentrations increased.

Abstract  Toluene, a volatile organic compound with a wide range of industrial applications, can exert neurotoxic and immunotoxic effects. However, the effects of toluene exposure on developmental immunotoxicity in the brain have not yet been characterized. To investigate the susceptible window to toluene exposure during development and the effects of fetal and neonatal toluene exposure on the neuroimmune markers, gestational day (GD) 14 pregnant mice, postnatal day (PND) 2 and PND 8 male offspring were exposed to filtered air (control; 0 ppm), or 5 or 50 ppm toluene for 6 h per day for five consecutive days. The neuroimmune markers in the hippocampus of PND 21 were examined using a real-time RT-PCR and immunohistochemical analysis. Mice exposed to 50 ppm toluene on PND 2-6 showed significantly increased levels of nerve growth factor (NGF) and tumor necrosis factor (TNF)-α mRNAs. In contrast, NGF and brain-derived neurotrophic factor (BDNF) and proinflammatory cytokines TNF-α, CCL3, NF-κB, toll-like receptor (TLR)-4, astrocyte marker glial fibrillary acidic protein (GFAP), and microglia marker ionized calcium binding adapter molecule (Iba)-1 mRNAs were increased significantly in mice exposed to 5 ppm toluene on PND 8-12. These results indicate that low-level toluene exposure during the late postnatal period (PND 8-12) might induce neuroinflammatory mediators via TLR4-dependent NF-κB pathway in the hippocampus of PND 21 male mice. Among the three developmental phases, PND 8-12 seems to be most sensitive to toluene exposure. This is the first study to show developmental phase- and dose-specific changes in neuroimmune markers in infant mice following toluene exposure.

Abstract  An investigation of the effect of relative humidity on aerosol formation from in-xylene and 1,3,5-trimethylbenzene photooxidation is reported, Experiments were performed in the presence and absence of ammonium sulfate seed particles (both aqueous and dry) to ascertain the effect of partitioning of oxidation products into a strong electrolytic solution or onto dry crystalline seed particles, In marked contrast to the alpha -pinene/ozone system, the final measured secondary organic aerosol yield was unaffected by the presence of gas-phase or liquid-phase water at relative humidities (RH) up to 50%. The hygroscopic nature of the aerosol generated upon photooxidation of m-xylene and 1,3,5-trimethylbenzene was examined; the hygroscopicity of the aerosol at 85% RH for both parent organics increased with the extent of the reaction, indicating that the first-generation oxidation products undergo further oxidation. Limited identification of the gas- and aerosol-phase products of in-xylene and 1,3,5-trimethylbenzene photooxidation is reported, It is evident that a more complete molecular identification of aromatic photooxidation aerosol awaits analytical techniques not yet brought to bear on this problem. (C) 2001 Elsevier Science Ltd. All rights reserved.

Abstract  In the crystal structure of the title compound, 4C(21)H(22)N(2)O(2)S(2)·0.5C(3)H(6)O·11.5H(2)O, there are four crystallographically independent mol-ecules (A, B, C, D) with similar geometries, 11 water mol-ecules and a solvent acetone mol-ecule which is disordered with a water mol-ecule with occupancy factors of 0.5:0.5. The dihedral angles formed by the mesitylene ring with the two pyridyl rings are 82.07 (3) and 78.39 (3)° in mol-ecule A, 86.20 (3) and 82.29 (3)° in mol-ecule B, 81.05 (3) and 76.0 (4)° in mol-ecule C, 86.0 (3) and 80.9 (3)° in moleule D. The two pyridyl rings form dihedral angles of 41.17 (4), 64.01 (3), 81.9 (3) and 82.25 (3)° in mol-ecules A, B, C and D, respectively. The crystal structure is stabilized by inter-molecular O-H⋯O hydrogen bonds and possible weak C-H⋯π inter-actions. Some short intra-molecular S⋯O contacts are apparent [2.684 (4)-2.702 (4) Å].

Abstract  A transition-metal-free synthetic method has been developed for the synthesis of unsymmetrical diaryl chalcogenides (S, Se, and Te) from diaryl dichalcogenides and arenes under oxidative conditions by using potassium persulfate at room temperature. Variously substituted arenes such as anisole, thioanisole, diphenyl ether, phenol, naphthol, di- and trimethoxy benzenes, xylene, mesitylene, N,N-dimethylaniline, bromine-substituted arenes, naphthalene, and diaryl dichalcogenides underwent carbon-chalcogen bond-forming reaction to give unsymmetrical diaryl chalcogenides in trifluoroacetic acid. To understand the mechanistic part of the reaction, a detailed in situ characterization of the intermediates has been carried out by (77)Se NMR spectroscopy by using diphenyl diselenide as the substrate. (77)Se NMR study suggests that electrophilic species ArE(+) is generated by the reaction of diaryl dichalcogenide with persulfate in trifluoroacetic acid. The electrophilic attack of arylchalcogenium ion on the arene may be responsible for the formation of the aryl-chalcogen bond.

Abstract  The reactivity of a nonheme iron(IV)-oxo complex, [(N4Py)Fe-IV(O)](2+) (N4Py = N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine), was markedly enhanced by perchloric acid (70% HClO4) in the oxidation of toluene derivatives. Toluene, which has a high one-electron oxidation potential (E-ox = 2.20 V vs SCE), was oxidized by [(N4Py)Fe-IV(O)](2+) Li in the presence of HClO4 in acetonitrile (MeCN) to yield a stoichiometric amount of benzyl alcohol, in which [(N4Py)Fe-IV(O)](2+) was reduced to [(N4Py)Fe-III(OH2)](3+). The second-order rate constant (k(obs)) of the oxidation of toluene derivatives by [(N4Py)Fe-IV(O)](2+) increased with increasing concentration of HClO4, showing the first-order dependence on [HClO4]. A significant kinetic isotope effect (KIE) was observed when mesitylene was replaced by mesitylene-d(12) in the oxidation with [(N4Py)Fe-IV(O)](2+) in the absence of HClO4 in MeCN at 298 K. The KIE value drastically decreased from KIE = 31 in the absence of HClO4 to KIE = 1.0 with increasing concentration of HClO4, accompanied by the large acceleration of the oxidation rate. The absence of KIE suggests that electron transfer from a toluene derivative to the protonated iron(IV)-oxo complex [(N4Py)Fe-IV(OH2)](3+) is the rate-determining step in the acid-promoted oxidation reaction. The detailed kinetic analysis in light of the Marcus theory of electron transfer has revealed that the acid-promoted C-H bond cleavage proceeds via the rate-determining electron transfer from toluene derivatives to [(N4Py)Fe-IV(O)](3+) through formation of strong precursor complexes between toluene derivatives and [(N4Py)Fe-IV(OH)](3+).

Abstract  Two halophilic, hydrocarbonoclastics bacteria, Marinobacter sedimentarum and M. flavimaris, with diazotrophic potential occured in hypersaline waters and soils in southern and northern coasts of Kuwait. Their numbers were in the magnitude of 10(3) colony forming units g(-1). The ambient salinity in the hypersaline environments was between 3.2 and 3.5 M NaCl. The partial 16S rRNA gene sequences of the two strains showed, respectively, 99 and 100 % similarities to the sequences in the GenBank. The two strains failed to grow in the absence of NaCl, exhibited best growth and hydrocarbon biodegradation in the presence of 1 to 1.5 M NaCl, and still grew and maintained their hydrocarbonoclastic activity at salinities up to 5 M NaCl. Both species utilized Tween 80, a wide range of individual aliphatic hydrocarbons (C-9-C-40) and the aromatics benzene, biphenyl, phenanthrene, anthracene and naphthalene as sole sources of carbon and energy. Experimental evidence was provided for their nitrogen-fixation potential. The two halophilic Marinobacter strains successfully mineralized crude oil in nutrient media as well as in hypersaline soil and water microcosms without the use of any nitrogen fertilizers.

Abstract  A very simple, fast and environmentally friendly sample extraction method was proposed for the analysis of phthalate esters (PAEs, di-isobutyl phthalate (DIBP), dibutylphthalate (DBP), butylbenzylphthalate (BBP) and bis(2-ethylhexyl)phthalate (DEHP)) in alcoholic beverages by using conventional ionic liquid dispersive liquid-liquid microextraction. The samples were extracted by 160μL 1-octyl-3-methylimidazolium hexafluorophosphate in the presence of appropriate amount of ethanol and 10% (w/v) sodium chloride solution; the enriched analytes in sedimented phases were analyzed by high performance liquid chromatography-diode array detector (HPLC-DAD). Under the optimum conditions, a satisfactory linearity (in the range of 0.02-1μgmL(-1) for white spirits and 0.01-0.5μgmL(-1) for red wines with the correlation coefficients (r) varying from 0.9983 to 1), acceptable recovery rates (88.5-103.5% for white spirits and 91.6-104.6% for red wines), good repeatability (RSD≤8.0%) and low detection limits (3.1-4.2ngmL(-1) for white spirits and 1.5-2.2ngmL(-1) for red wines) were obtained. The developed method was successfully applied for the determination of the four PAEs in 30 white spirits and 11 red wines collected locally, and the DBP content in 63% (19:30) white spirits exceeded the specific migration limit of 0.3mgkg(-1) established by international regulation.

Abstract  In 1229 subjects, 521 males and 708 females, with a wide range in body mass index (BMI; 13.9-40.9 kg/m2), and an age range of 7-83 years, body composition was determined by densitometry and anthropometry. The relationship between densitometrically-determined body fat percentage (BF%) and BMI, taking age and sex (males = 1, females = 0) into account, was analysed. For children aged 15 years and younger, the relationship differed from that in adults, due to the height-related increase in BMI in children. In children the BF% could be predicted by the formula BF% = 1.51 x BMI-0.70 x age - 3.6 x sex + 1.4 (R2 0.38, SE of estimate (SEE) 4.4% BF%). In adults the prediction formula was: BF% = 1.20 x BMI + 0.23 x age - 10.8 x sex - 5.4 (R2 0.79, SEE = 4.1% BF%). Internal and external cross-validation of the prediction formulas showed that they gave valid estimates of body fat in males and females at all ages. In obese subjects however, the prediction formulas slightly overestimated the BF%. The prediction error is comparable to the prediction error obtained with other methods of estimating BF%, such as skinfold thickness measurements or bioelectrical impedance.

Abstract  The reaction of hydrogen with mesitylene, p-xylene, toluene, and benzene has been studied on Pt/carrier catalysts in the gas phase between 30 and 110 °C. The hydrogenation is associated with a low temperature hydrogenolysis of the methyl substituents. This new low temperature hydrogenolysis of alkylbenzenes significantly differs from the hydrogenolysis of paraffins and from high temperature hydrocracking. Hydrogenation and hydrogenolysis are parallel reactions. A mechanism of hydrogenolysis is proposed. © 1976.

Abstract  Third-order rate coefficients have been determined at 295 K for the formation of dimeric parent cations in benzene, benzene-d6, toluene, the xylenes, mesitylene, and fluoro- and chlorobenzene using the NBS high pressure photoionization mass spectrometer. The reactions are all quite fast, the rate coefficients falling in the range 0.5-6 · 10-25 cm6 molecule-2 s-1. The differences in rates observed are rationalized in terms of structural (geometric) considerations, and upper limits are established for the binding energies in (C6H6)2+ and (C6H5CH3)2+. The temperature dependence for production of (C6D6)2+ has been determined from 227 to 316 K, and the rate coefficient seems to obey a simple 1/T relationship over this range. The detection of trimeric species in benzene is also reported for the first time. Additional experiments involving benzene-nitric oxide mixtures are also reported, which include detection of an apparent equilibrium of the type NO+ + C6H6 ⇆ C6H6+ + NO. © 1976.

Abstract  Physisorption and heat of immersion measurements have been made with two microporous carbons-a sample of charcoal cloth (BET area, 1250 m2 g-1; pore volume, 0.59 cm3 g-1 having predominantly narrow micropores and a sample of Amoco carbon (BET area, 3700 m2 g-1; pore volume, 1.9 cm3 g-1), having a wider distribution of micropores extending into the supermicropore range (pore width, ca. 1-2 nm). The adsorption isotherms of nitrogen and toluene are of Type 1 and reveal that the external surface of both samples is very small. The heat of immersion measurements were carried out with the aid of a Tian-Calvet microcalorimeter and with the following liquids: n-hexane, cyclohexane, neo-hexane, toluene, mesitylene and isodurene. A sample of non-porous graphitized carbon black (Vulcan 3G: BET area, 71.1 m2 g-1) was studied. Immersion calorimetry shows that in spite of the larger adsorptive capacity of the Amoco carbon, the sample of charcoal cloth has a higher adsorption affinity. The differences in the corresponding heats of immersion and in the adsorptive properties indicate that many of the pores in charcoal cloth are slit-shaped, whereas those in the Amoco carbon appear to be more cylindrical in shape. 1982.

Abstract  Computational techniques based on molecular mechanics and dynamics can be effectively exploited for supporting the development of new processes based on the use of zeolite-based catalysts. The availability of efficient modeling tools and accurate energy parameters (force fields) allows the shape selectivity properties of zeolites to be rapidly evaluated and even predicted. This may limit the otherwise onerous and time-consuming experimental screening tests, increasing in the same time the probability to successfully identify the most promising catalyst for a given reaction. Some case studies are here reported illustrating the role of computational techniques in the development of new processes for the synthesis of cumene, 2,6-dimethylnaphtahlene, mesitylene and durene.

Abstract  New chelating ligands consisting of three beta-diketone fragments, viz., 1,3,5-tris[(acetylaceton-3-yl)methyl]benzene, 1,3,5-tris[(benzoylaceton-3-yl)methyl]benzene, and 1,3,5-tris[(dibenzoylmethan-1-yl)methyl]benzene, linked to each other through the mesitylene spacer were synthesized by the reaction of 1,3,5-tris(bromomethyl)benzene with the corresponding beta-diketone sodium salt. The acidity of these compounds and their complexation properties were studied by pH-potentiometry in aqueous-ethanol solutions. Tris(beta-diketones) form mononuclear complexes with lanthanide ions, whose stability increases in the series La3+ < Gd3+ < Lu3+. 1,3,5-Tris[(acetylaceton-3-yl)methyl]benzene forms both mononuclear and polynuclear complexes with the Ni2+ and Cu2+ ions. The stability constants and selectivity of complex formation increase substantially with an increase in the degree of deprotonation of the ligands, thus indicating that all deprotonated chelate groups are involved in coordination with the metal ion. The replacement of the methyl groups by the phenyl substituents in the beta-diketone fragments of the molecules affects substantially the composition and stability of the complexes formed.

Abstract  A new fluorescent probe 3, has been developed for the detection of Fe(III) in water based samples. The design of 3 involved the incorporation of Fe(III) binding sites observed in naturally occurring Siderophores into a synthetic sensing assembly. The probe, containing two Schiff base receptors connected to a mesitylene platform, was prepared in two steps. The dipodal sensor displayed good selectivity for Fe(III) when tested against other physiological and environmentally important metal ions, in HEPES buffered solution at pH 7.0, through a quenching of the fluorescent intensity. Stern-Volmer analysis of this quenching interaction indicated a 1:1 (host : guest) binding stoichiometry between the probe and Fe(III). The association constant, K(a) calculated using the Benesi-Hildebrand equation was found to be 3.8 x 10(4) M(-1). Crucially, the sensor was capable of measuring Fe(III) competitively in solutions containing both Fe(III) and Cu(II). Thus, the adoption of Fe(III) binding sites found in nature, into synthetic luminescent assemblies has proven an effective design strategy for the development of new Fe(III) probes.

Abstract  The densities, rho, of binary mixtures of butyl acrylate (BA) with benzene, toluene, o-xylene, m-xylene, p-xylene, and mesitylene, including those of pure liquids, over the entire composition range were measured at the temperatures (288.15, 293.15, 298.15, 303.15, 308.15, 313.15, and 318.15) K and atmospheric pressure. From the experimental data, the excess molar volumes, V(m)(E) were calculated. The V(m)(E) values were negative over the whole composition range for all the mixtures and at each temperature studied, except for BA + mesitylene which exhibit positive V(m)(E) values, indicating the presence of specific interactions between BA and aromatic hydrocarbon molecules. The deviations in V(m)(E) values follow the order: benzene<toluene<p-xylene<m-xylene<o-xylene<mesitylene. It is observed that V(m)(E) values depend upon the number and position of the methyl groups in these aromatic hydrocarbons.

Abstract  It has been demonstrated that the main diffusion paths of micro- and meso-porous UL-zeolites could be characterized from the Zero Length Column (ZLC) desorption curves with an appropriate theoretical analysis (Malekian et al., in Ind. Eng. Chem. Res. 46:5067, 2007). The present work extends this method to study the ZLC desorption data of n-heptane/cumene/mesitylene in three mesoporous SBA-15 samples, 1-methylnaphthalene in MCM-48, cumene in SBA-16 and toluene/cumene in a microporous one-dimensional boron SSZ-42. The investigation results revealed that the structure of SBA-15, MCM-48 and SBA-16 behaved approximately as three-dimensional (isotropic) diffusion system, while SSZ-42 behaved as one-dimensional (anisotropic) diffusion systems. The diffusion path did not change within the measured temperature range, and by using different sorbate molecules. This work confirmed that this effective and relatively inexpensive method can be used as an additional tool for the characterization of porous materials.