Structural elucidation by 1D and 2D NMR of three isomers of a carotenoid lysophosphocholine and its synthetic precursors

A carotenoic acid was used to obtain a long-chain unsaturated lysophosphocholine. The carotenoid lysophosphocholine was synthesized by two methods. The first method resulted in mixtures of regioisomers for each step in the synthetic route. Homo- and heteronuclear 1D and 2D NMR methods were employed to elucidate the structures of the individual isomers and their intermediates. The pure regioisomer [1-(beta-apo-8'-carotenoyl)-2-lyso-glycero-3-phosphocholine] was obtained by a second method, but in low yield. The 1D 1H NMR subtraction spectrum of the mixture and the pure regioisomer was used to interpret the 1H shifts of the unsaturated acyl moieties. The 1H and 13C signals of the acyl chain show characteristic shifts depending on the positions of the choline and the acyl group attached to the glycerol backbone. Therefore, the unsaturated acyl chain signals have diagnostic values for the identification of isomers of unsaturated (lyso)phosphocholines. Chemical shifts and indirect coupling constants are reported for each of the major components of the mixtures. The methods used were 1D (1H, 13C and 31P) and 2D (H,H-COSY, HMBC, HSQC and HETCOR) NMR.     

Nuclear structure studies of187Ir via on-line nuclear orientation

A more complete level scheme is presented here for the decay of¹⁸⁷Pt, incorporating many new lines and levels up to 2.4 MeV. Emphasis has been placed on the extraction of multipole mixing ratios from nuclear orientation data. Analysis of that data, however, required a more complete understanding of the level structure (including, in particular, branching ratios, conversion coefficients, and level feedings), prompting the collection of new spectroscopy data. The low-lying, positive-parity levels are described in terms of (odd-proton) single-particle Nilsson states coupled to a triaxial core. Multipole mixing ratios are compared to those calculated in the Particle-Plus-Triaxial-Rotor Model.     

Studies of crown ether complexes aryldiazonium ion complexes

DNMR studies show that for complexation of aryldiazonium salts 21-crown-7 is the preferred host.     

Structure elucidation of C80, C81 and C82 isoprenoid tetraacids responsible for naphthenate deposition in crude oil production

A series of C(80) isoprenoid 20-bis-16,16'-biphytanyl tetraacids has previously been found to be responsible for calcium naphthenate scaling in crude oil processing. This paper describes the structure elucidation by high-field NMR spectroscopy of the structures of the series of homologous C(80) tetraacids containing 4-8 five-membered rings. In addition, the structures of methyl-substituted C(81) and C(82) analogues containing 7 and 8 five-membered rings have been determined for the first time. The biosynthetic implications are discussed.     

Investigation into the enantioselection mechanism of ruthenium-arene-diamine transfer hydrogenation catalysts using fluorinated substrates

The effects of both steric and electronic properties of ketones on the selectivity in asymmetric transfer hydrogenation have been studied with aryl alkyl/fluoroalkyl ketones using four ruthenium based catalysts and two different media. The 1-arylethanones, 1-aryl-2-fluoroethanones and 2,2-difluoroacetophenones could be reduced with medium to high ee (86-99%), while the 1-aryl-2,2,2-trifluoroethanones were reduced with low selectivity in most systems. The change in enantioselectivity upon structural variation has been rationalised aided by regression analysis with substituent constants and the partial charge of the carbonyl carbon as predictors. The steric bulk of the alkyl/fluoroalkyl chain was found to be the major factor in determining selectivity in formic acid/triethylamine, while for reduction of a series of substituted 1-arylethanones and 1-aryl-2-fluoroethanones, the selectivity was found to depend on the electronic properties of the aromatic ring, supporting previous evidence that π-π interaction between the substrate and catalyst is important in determining the selectivity. For reductions in water using sodium formate as the hydrogen donor, altered and more complex selectivity mechanisms were observed. Experiments and regression focused on the variation of the alkyl/fluoroalkyl group of phenyl and 1-naphthyl ketones, showed that the selectivity correlated with the size of the substituent, but also the partial charge of the carbonyl carbon.     

NMR study and quantum mechanical calculations on the 2-[(2-aminoethyl)amino]-ethanol-H2O-CO2 system

13C and 1H NMR spectra were obtained for AEEA (2-[(2-aminoethyl)amino]-ethanol)-H2O-CO2 systems and quantum mechanical calculations were carried out for the different AEEA species. The results suggest that the main AEEA species under the conditions studied are free amine, primary carbamate, and secondary carbamate. There is also some indication that a dicarbamate species is formed, this species does however only appear to be formed in small amounts. Comparison between experimental data and quantum mechanical calculations suggest that most AEEA species take on conforms with some degree of intramolecular hydrogen bonding.     

Radial profiles of deposition nozzles for high uniformity

An important design problem is concernedwith uniform wetting of plane areas using arrays of spraying nozzles. Good uniformity requires that the radial profile of deposition from the nozzles, as well as the array spacing, be carefully chosen. The purpose of this paper is to present a technique for computing nozzle profiles which result in high uniformity when used in particular array configurations. The method is based on a spline model for the nozzle, with coefficients determined by minimizing the absolute deviation from mean deposition. Results for square, rectangular, and triangular arrays are presented.     

UNISOR on-line nuclear orientation facility (UNISOR/NOF)

The UNISOR on-line nuclear orientation facility (UNISOR/NOF) consists of a₃He−₄He dilution refrigerator on line to the isotope separator. Nuclei are implanted directly into a target foil which is soldered to the bottom accessed cold finger of the refrigerator. A 1.5 T superconducting magnet polarizes the ferromagnetic target foils and determines the axis of symmetry. Up to eight gamma detectors can be positioned around the refrigerator, each 9 cm from the target. A unique feature of this system is that the k=4 term in the directional distribution function can be directly and unambigously deduced so that a single solution for the mixing ratio can be found. The first on-line experiment at this facility reported here was a study of the decay of the¹⁹¹Hg and¹⁹³Hg isotopes.     

Determination of trace amounts of polycylic aromatic hydrocarbons in soil

Summary A method is described for the determination of polycyclic aromatic hydrocarbons in natural soil. The soil is dried and extracted by ultrasonic agitation with dichloromethane. The extract is purified by liquid-liquid partitioning with dimethylformamide, water and hexane followed by high performance liquid chromatography on a silica column. Quantitative analysis of the purified extract is carried out by combined gas chromatography/mass spectrometry. The method yields reliable results at the ng/g level.

---

Bestimmung von Spuren polycyclischer aromatischer Kohlenwasserstoffe in Boden

     

On-line nuclear orientation of odd-odd120I

The use of Low Temperature Nuclear Orientation (LTNO) in nuclear structure studies is discussed. LTNO has been employed, together with γ-γ and e-γ spectroscopy, to study the nuclear structure of¹²⁰Te following the beta decay of¹²⁰ I ^g . The strengths and limitations of LTNO as a probe of nuclear structure are discussed with particular reference to this experiment.