The mass spectra of some naphthoquinones. Lapachol,isolapachol and related compounds

Several alkylhydroxynaphthoquinones and chemically related cyclic compounds were subjected to mass spectrometric investigation. Fragmentation pathways were elucidated by use of metastable ions, relative intensities of normal ions and accurate mass measurement. In these series, differences in the spectra of 1,2- and 1,4-naphthoquinones are slight. Evidence for ring expansion in ions from furans is suggested.     

The non-existence of gaseous cyclopentadienyl cations: An overdue correction to the literature using collision-induced decompositions and charge stripping of negative ions

The C₅H₅⁺ fragment ion bound in many EI spectra is determined not to be cyclopentadienyl cation by CID-MIKE spectrometry.     

Hybrid character and rotational analysis of the 2700 Å band of m-fluorochlorobenzene

The rotational structure of the 2700 Å (π^∗←π) transition of m-chlorofluorobenzene is observed and analyzed. Assuming the molecule to be planar in the excited state, the changes in rotational constants are found to be

δA=−0.0035cm⁻¹

Comparison between the point-charge electrostatic model and the angular overlap model: The general case

The aim of this paper is to explore in detail the mathematical connection between the point-charge electrostatic model and the angular overlap model. More precisely, for any configuration nl^x in any symmetry, the matrix elements, and therefore the energy levels, as given by the angular overlap model restricted to the antibonding effects λ (for any of the possible λ's), are deduced from an effective potential constructed according to the point-charge electrostatic model. This allows us to give a mathematical proof of the equivalence between the point-charge electrostatic model and the angular overlap model taking into account all the antibonding effects λ. Finally, the sum rules for the angular overlap model are examined in the light of the formulae connecting the two models considered. Numerical tables for obtaining the results as given by the angular overlap model restricted to any of the antibonding effects from those as given by the point-charge electrostatic model are listed for the configurations nl^x with l = p, d, f and g.     

Simultaneous two-frequency oscillation in a dye laser system

We describe a continuously tunable dye laser operating two-wavelengths simultaneously over a tuning range of about 250 Å. With a beam splitter, two polarizers and two gratings the two output beams are spatially coherent and can be of any desirable polarizations with respect to each other.     

Parviflorine,a glycosidic spirobenzylisoquinoline alkaloid

(+)-Parviflorine ($\text{1}$), found in $\text{Fumaria parviflora}$ Lam. (Fumariaceae), is the first known glycosidic spirobenzylisoquinoline alkaloid. Its acid hydrolysis yields (+)-parfumine ($\text{4}$) and D-glucose. Klyne's rule indicates that $\text{1}$ is a β-D-glucoside. The absolute configuration shown in expressions $\text{1-11}$ is predominant among spirobenzylisoquinolines. A generalization has been drawn between plant source and the oxygenation pattern of ring C for the spirobenzylisoquinoline alkaloids.     

Proton magnetic resonance spectra of substituted adamantane-2,4-diones. Determination of the C-6 and C-9 stereochemistry

The 220 MHz ¹H NMR spectra of 6-hydroxy-7-methyl-6-phenyladamantane-2,4-dione, 6-hydroxy-5,7-dimethyl-6-phenyladamantane-2,4-dione, and 6-hydroxy-7,9-dimethyl-6-phenyladamantane-2,4-dione have been determined and complete proton assignments carried out with the aid of multiple irradiation. The stereochemistry of the C-6 and C-9 chiral centres have been determined and some of the factors affecting the magnitude of the geminal, vicinal and W coupling constants are discussed.     

Hyperpolarization of 13C through order transfer from parahydrogen: a new contrast agent for MRI

The order within proton pairs in organic molecules, resulting from hydrogenation with parahydrogen, can be transferred in great part to nearby carbon 13 spins through adequate field manipulations. The molecules with hyperpolarized 13C thus obtained can be used as new contrast agents of high efficiency in MRI. After a brief presentation of the hydrogenation process and apparatus, in relatively low magnetic field, we describe the procedure of order transfer to the 13C spins through a sudden drop from the initial field to zero field followed by an adiabatic remagnetization. The expected final polarizations in the absence of relaxation are given for several compounds. Finally, we show an example of MR images observed in vivo on animals as an illustration of the contrast capacity of this new method.