Rotational and hyperfine parameters of NH2(X2B1) from LMR spectra

Seventeen rotational transitions up to N=7 of the NH₂ radical in its ground vibronic state have been measured by far infrared laser magnetic resonance spectroscopy. Analysis of the Zeeman patterns and hyperfine structure yields precise rotational, spin-rotational and distortion parameters, and isotropic and anisotropic hyperfine interaction parameters for both ¹⁴N and ¹H nuclei.     

Surface tension of a Lennard-Jones liquid under supersaturation

A formally exact Kirkwood-Buff virial formula for the surface tension of a supersaturated interface is derived. A modified Gibbs ensemble method is given that allows the creation of interacting supersaturated phases of equal chemical potential, and which enables the Kirkwood-Buff formula to be applied. The methods are tested by Monte Carlo simulation of a supersaturated Lennard-Jones fluid with a planar liquid-vapor interface. The Kirkwood-Buff results for the supersaturated surface tension are found to be in reasonable agreement with new results obtained here using the recently developed, formally exact, ghost interface method, [M. P. Moody and P. Attard, J. Chem. Phys., 2002, 117, 6705]. The surface tension is obtained as a function of supersaturation at four temperatures, and it is found to decrease with increasing supersaturation, and to vanish at the vapor spinodal. The relevance of the present results to the nucleation of droplets in a supersaturated vapor is discussed.     

Analysis of turkish lignite tar by coupled LC/GC,GC/MS,and capillary SFC

This work describes the analysis of a pyrolysis product of a lignite sample obtained from the Turkish Goynuk reserve. The aliphatic, aromatic and polar compounds present in the tar are separated and identified by various chromatographic techniques: Capillary gas chromatography/mass spectrometry (GC/MS), on-line high performance microbore liquid chromatography/capillary gas chromatography (LC/GC) and capillary supercritical fluid chromatography (SFC). The suitability of each technique for this particular application is discussed, and semi-quantitative results are presented for the major components detected.     

Solid-state vibrational spectroscopy: Part VI. An infrared and raman spectroscopic study of transition metal(II)4-methylpyridine complexes

Infrared (4000–200 cm^?1) and Raman (3500–300 cm^?1 ) spectra are reported for metal(II) halide and thiocyanate 4-methylpyridine complexes of the following stoichiometries: (MX₂(4-Mepy)₂) {M = Mn, Co, Cu or Zn, X = Cl or Br; M = Mn, Ni or Zn, X = NCS}; (MX₂(4-Mepy)₄) {M = Mn, Fe, Co or Ni, X = Cl or Br; M = Mn, Fe, Co, W or Cu, X = NCS}. For a given series of isomorphous complexes there is a correlation between the sum of the differences between the liquid and ligand values of the ν₁, ν₂, ν₃, ν₄, ν₅, ν₆, ν₇, ν₈, ν₉, ν₁₀, ν₁₂, ν₁₃ and ν₁₄ modes of 4-methylpyridine and the strength of the metal-nitrogen bond. Comparison of the shift values of pyridine and 4-methylpyridine complexes supports the suggestion that, unlike the situation in the pyridine complexes, back-donation from the metal to the ligand is unimportant in the 4-methylpyridine complexes.     

Indium-mediated beta-allylation,beta-propargylation,and beta-allenylation onto alpha,beta-unsaturated ketones: reactions of in-situ-generated 3-tert-butyldimethylsilyloxyalk-2-enylsulfonium salts with in-situ-generated organoindium reagents

3-tert-Butyldimethylsilyloxyalk-2-enylsulfonium salts, generated in situ from the reaction of alpha,beta-enones with dimethyl sulfide in the presence of TBSOTf, underwent a novel nucleophilic substitution with allylindiums to give silyl enol ethers of delta,epsilon-alkenyl ketones in good yields, which correspond to formal Michael addition products. In a similar manner, 1,4-propargylation of propargylindiums onto the sulfonium salts produced the corresponding silyl enol ethers of delta,epsilon-alkynyl ketones in good yields. Organoindium reagents derived from gamma-substituted propargyl bromide and indium afforded the corresponding silyl enol ethers of beta-allenyl ketones in good yields. The reaction proceeds via an addition-substitution mechanism involving the formation of allylic sulfonium salts. The presence of the intermediate sulfonium salt was confirmed by observation of the low-temperature (1)H NMR spectra.     

Ionic liquid analogues formed from hydrated metal salts

A dark green, viscous liquid can be formed by mixing choline chloride with chromium(III) chloride hexahydrate and the physical properties are characteristic of an ionic liquid. The eutectic composition is found to be 1:2 choline chloride/chromium chloride. The viscosity and conductivity are measured as a function of temperature and composition and explained in terms of the ion size and liquid void volume. The electrochemical response of the ionic liquid is also characterised and it is shown that chromium can be electrodeposited efficiently to yield a crack-free deposit. This approach could circumvent the use of chromic acid for chromium electroplating, which would be a major environmental benefit. This method of using hydrated metal salts to form ionic liquids is shown to be valid for a variety of other salt mixtures with choline chloride.     

Light induced interactions of benzo[a]pyrene with carboxylic acids

Abstract The in vitro photochemical behaviour of benzo[a]pyrene (BP) in presence of short and long chain carboxylic acids is studied. The direct irradiation (295–400 or 320–400 nm) of BP in solution in the presence of saturated carboxylic acids destroys more than 70% of this carcinogen in 72 h with a 150 W Xe arc lamp. Consumption of BP alone under similar conditions is less than 10%. The principal product resulting from direct interaction of BP with carboxylic acids is characterized as 6-acyloxybenzo[a]pyrene by means of UV, IR, NMR and mass spectroscopy. The other pathways of destruction may involve polymerization. Saturated fatty acids are shown to favour photoacyloxyation, while unsaturated fatty acids appear to facilitate polymerization of BP. The effect of different factors, such as the carboxylic acid involved, solvent, and wavelength on photoacyloxylation reaction as well as on the consumption of BP is discussed. Photoinduced interaction of BP with carboxylic acids seems to involve radical cation as well as free radicals of the hydrocarbon. Biological properties of BP esters in terms of primary irritancy and carcinogenic activity have also been tested by mouse skin assay. Both long and short chain esters do not show any carcinogenic activity; conversely, long chain esters are shown to be more severe irritants as compared to short chain esters or BP.     

Cyclization of 1-bromo-2,7- and 1-bromo-2,8-enynes mediated by indium

[reaction: see text] The cyclization of 1-bromo-2,7- and 1-bromo-2,8-enynes mediated by indium in DMF produced five- and six-membered cyclic compounds. Although KI was a necessary additive in the cyclization of terminal 1-bromo-2,7-enynes to give the desired products at 25 degrees C, reactions of terminal 1-bromo-2,8-enynes and internal 1-bromo-2,7-enynes with indium proceeded at 100 degrees C in DMF without KI. After cyclizations, subsequent cross-coupling reaction and iodolysis increase the usefulness of this reaction.     

Development of an automated method for determining oil in water by direct aqueous supercritical fluid extraction coupled on-line with infrared spectroscopy

A direct aqueous supercritical fluid extraction (SFE) system was developed which can be directly interfaced to an infrared spectrometer for the determination of oil in water. The technique is designed to provide an environmentally clean, automated alternative to established IR methods for oil in water analysis which require the use of restricted organic solvents. The SFE-FTIR method involves minimum sample handling stages, with on-line analysis of a 500 ml water sample being complete within 15 min. Method accuracy for determining water samples spiked with gasoline, white spirit, kerosene, diesel or engine oil was 81-100% with precision (RSD) ranging from 3 to 17%. An independent evaluation determined a 2 ppm limit of quantification for diesel in industrial effluents. The results of a comparative study involving an established IR method and the SFE-FTIR method indicate that oil levels calculated using an accepted equation which includes coefficients derived from reference hydrocarbon standards may result in significant errors. A new approach permitted the derivation of quantification coefficients for the SFE-FTIR analyses which provided improved results. In situations where the identity of the oil to be analysed is known, a rapid off-line SFE-FTIR system calibration procedure was developed and successfully applied to various oils. An optional in-line silica gel clean-up procedure incorporated within the SFE-FTIR system enables the same water sample to be analysed for total oil content including vegetable oils and selectively for petroleum oil content within a total of 20 min. At the end of an analysis the SFE system is cleaned using an in situ 3 min clean cycle.