Search results for "alkane"

Determination of barbiturates in urine by micellar liquid chromatography and direct injection of sample.

2000

Abstract A liquid chromatographic procedure for the determination of six barbiturates (barbital, diallyl barbituric acid, phenobarbital, butabarbital, amobarbital and pentobarbital) in urine samples is described. The proposed system uses a Spherisorb octadecyl-silane ODS-2 C 18 analytical column and a guard column of similar characteristics. The UV detector was set at 240 nm. A study to select adequate composition of the micellar mobile phase for the separation of these compounds in urine samples is performed. Maximum resolution was achieved with a 0.07 M sodium dodecylsulphate-0.3% propanol at pH 7.4 eluent. Limits of detection at 240 nm were ranged between 0.13 μg ml −1 for diallyl barbit…

A thermodynamic study to evidence the alpha,omega-dichloroalkane/ block copolymer mixed aggregates formation: effect of the copolymer architecture.

2006

Abstract The thermodynamics of α , ω -dichloroalkanes in aqueous solutions of (ethylene oxide)11(propylene oxide)16(ethylene oxide)11 (L35) and (propylene oxide)8(ethylene oxide)23(propylene oxide)8 (10R5) was determined at 298 and 305 K. Modeling the experimental data allowed to calculate the standard free energy ( Δ G D o / w ) and the volume ( Δ V D / w ) for the additive–copolymer mixed aggregates formation per additive molecule. Δ G D o / w for Cl2CH2 and Cl2(CH2)2 evidenced that the process is controlled by the forces exercising between the chlorine atoms and the OH groups of the copolymer micelles protruded into the aqueous phase. Cl2(CH2)3 experiences both the hydrophilic and hydrop…

GENE CLONING AND CHRACTERIZATION OF AN ALKANE HYDROXYLASE SYSTEM IN A LONG CHAIN N.ALKANE. DEGRADER GORDONIA SP.

2008

1-Benz­yloxy-1H-benzotriazole

2012

In the title compound, C13H11N3O, the dihedral angle between the benzotriazole ring system [maximum deviation = 0.027 (16) Å] and the benzene ring is 10.28 (9)°. The C—C—O—N bond adopts an anti conformation [torsion angle = −177.11 (16)°]. In the crystal, the molecules interact via weak C—H...π interactions and aromatic π–π stacking [centroid-to-centroid distance = 3.731 (12) Å].

Effect of temperature and organic nutrients on the biodegradation of linear alkylbenzene sulfonate (LAS) during the composting of anaerobically diges…

2004

Limits on the application of biosolids (anaerobically processed sludges from wastewater treatment plants) as fertilizers for the amendment of soil are becoming greater because of the accumulation of recalcitrant substances, making necessary the use of techniques that bring the concentration of xenobiotics to lower concentrations than those permitted. In general, the biosolids composting process is sufficient to reduce the usual concentration of linear alkylbenzene sulfonates (LAS) to low levels. In this work, an assessment is made on the effect of temperature in the capacity of enriched bacterial populations to biodegrade LAS, together with the influence that the available nutrients may hav…

A Modular Synthesis of Polysubstituted Indolizines

2012

The N-alkylation of pyridines with cyanohydrin triflates or α-halonitriles furnishes 1-(1-cyanoalkyl)pyridinium salts that can react with nitroolefins under basic conditions to furnish polysubstituted indolizines. Overall, the indolizine core can be constructed from a pyridine, two aldehydes, and a nitroalkane, and no undesired functional groups remain in the products. When bromoacetonitrile was used for the N-alkylation, indolizine-3-carbonitriles were obtained instead. The pyridine component may be replaced by other azines, giving rise to related heterocyclic systems.

Classification of vegetable oils according to their botanical origin using n-alkane profiles established by GC-MS.

2013

n-Alkane profiles established by gas chromatography-mass spectrometry (GC-MS) were used to classify vegetable oils according to their botanical origin. The n-alkanes present in corn, grapeseed, hazelnut, olive, peanut and sunflower oils were isolated by means of alkaline hydrolysis followed by silica gel column chromatography of the unsaponifiable fractions. The n-alkane fraction was constituted mainly of n-alkanes in the range C8-C35, although only those most abundant (15 n-alkanes, from 21 to 35 carbon No.) were used as original variables to construct linear discriminant analysis (LDA) models. Ratios of the peak areas selected by pairs were used as predictors. All the oils were correctly …

MINDO/3 Study of the Rearrangement of 1-Methylcyclohexyl Cation to 1,2-Dimethylcyclopentyl Cation

1986

The rearrangement of the 1-methylcyclohexyl cation to the 1,2-dimethylcyclopentyl cation has been studied by MINDO/3 calculations, as an application of the branching mechanism model for cycloalkanes. Possible intermediates and transition states have been characterized by diagonalization of their Hessian matrixes. Two nonequivalent pathways, α and β scissions, are relatively close in energy. The calculated transition states are almost equivalent in energy to those found for cyclohexyl cation. Hence, the energy barriers are higher for the rearrangement of the 1-methyl than for cyclohexyl cation, because the former is less stable than the latter.

Chemistry and reactivity of dinuclear iron oxamate complexes: alkane oxidation with hydrogen peroxide catalysed by an oxo-bridged diiron(III) complex…

2004

[EN] A new dinuclear iron(III) complex with the tetradentate ligand N,N'-o-phenylenebis(oxamate) (opba) has been synthesised, and structurally, magnetically and electrochemically characterised. It possesses an unprecedented triply bridged Fe-2(mu-O)(mu-RCO2...H2O...O2CR)(2) core, whereby two N-amides from the opba ligand complete the square-pyramidal coordination sphere of the O-carboxylate rich iron site (Fe-N = 2.053 Angstrom and Fe-O = 2.015 Angstrom), The antiferromagnetic exchange interaction between the two high-spin Fe-III ions through the oxo bridge (J = -190 cm(-1); H = -JS(1)(.)S(2)) is weaker than that found in related mu-oxo singly bridged diiron(III) complexes. The lessened ant…

Alkane oxidation by a carboxylate-bridged dimanganese(III) complex

2001

[EN] A new manganese( III) oxamato dimer possesing an unprecedented Mn-2(mu -O2CR)(mu -OH2. . .O2CR) core has been synthesised, structurally and magnetically characterised, and used as a catalyst for the oxidation of alkanes to alcohols and ketones by (BuO2H)-O-t and O-2 in CH2Cl2 at rt.