13C NMR spectra of pyridinium betaines and related compounds

¹³C NMR spectra of 1-methyl-, 1-phenyl- and 1, 6-dimethyl-pyridinium-3-oxide, 3-methylphthalazinium 1-oxide and anhydro-3-methanesulphonamido-1-methylpyridinium hydroxide, together with the corresponding amines and quaternary salts, were determined with and without proton noise-decoupling. The assignment of resonances was based on the analysis of the fine splitting pattern caused by long range couplings whenever appropriate. A procedure for the estimation of chemical shifts of the salts and betaines is proposed.     

Lattice vibrations of polymethylene crystal

The energy levels of the lattice vibrations of orthorhombic polymethylene crystal was calculated quantum-mechanically. The rotational modes were treated in the same manner as employed for the internal-rotation problem. For the translational modes the energy levels were obtained from perturbation calculations. The results clearly indicated that the anharmonicities have significant effects on the lattice modes, the A_g rotational mode in particular.     

Solvent gradient elution in micro HPLC

A simple gradient method for capillary column and micro high performance liquid chromatography using either single or multiple mixing chambers is presented. The gradient profile is dependent on the number of the mixing chambers. This system permits solvent gradient elution at flow rates less than 10 μl/min with satisfactory reproducibility.     

Lifetime spectra of positrons in deformed Ge

Positron lifetime measurements have been performed inn-type andp-type germanium single crystals deformed by compression. The results are compared with those of deformed GaAs single crystals obtained by the authors previously. In bothn andp-type germanium the lifetime τ₁ and its intensityI ₁ decreased with deformation. Using the trapping model, the trapping rates of positrons by dislocations are obtained, which in turn gave the cross width of the dislocation as 20.0 Å and 8.2 Å forn-type andp-type germanium, respectively. In terms of Read's model the fraction of the dangling bonds occupied by electrons is obtained to 0.26 in then-type germanium. This value was smaller than those obtained forn-type GaAs, i.e., 0.46 and 0.50 for Ga- and As-dislocation, respectively. It is found that doping causes the trapping of positrons. Inp-type germanium the fractionf was determined to 0.25 in terms of Schröter and Labusch's model.     

Access to a stable Si2N2 four-membered ring with non-Kekulé singlet biradical character from a disilyne

The reactions of 1,1,4,4-tetrakis[bis(trimethylsilyl)methyl]-1,4-diisopropyltetrasila-2-yne 1 with an equivalent amount of trans- and cis-3,3',5,5'-tetramethylazobenzenes produced a Si(2)N(2) four-membered ring biradicaloid [RSi(μ-NAr)(2)SiR] 2 (R = Si(i)Pr[CH(SiMe(3))(2)](2), Ar = 3,5-Me(2)C(6)H(3)), which was isolated as air- and moisture-sensitive dark purple crystals. Compound 2 displays no EPR signal, and the molecular structure of 2 was characterized by NMR spectroscopy and X-ray crystallography, revealing that 2 has a planar centrosymmetric Si(2)N(2) four-membered ring. The Si1-Si1' distance is 2.63380(9) ?, and there is no bond interaction between the Si1 and Si1' atoms of 2. The reactions of 2 with methanol and carbon tetrachloride show that 2 has both closed-shell and radical-type reactivity.     

Enantio-selective reduction of the flowering related compound KODA and its analogues in Pharbitis nil cv. Violet

Plant oxylipins are an important class of signaling molecules in plants. The cyclic adducts of epinephrine or norepinephrine with the naturally occurring oxylipin (12Z,15Z)-9-hydroxy-10-oxo-octadeca-12,15-dienoic acid (KODA, 1) or its synthetic analogues (2–6) have been reported to possess flower-inducing activity toward Lemna paucicostata. By in vivo and in vitro experiments with seedlings of Pharbitis nil cv. Violet carbonyl groups of the α-ketols (1 and 3) and the ketones (7 and 9) were enantio-selectively reduced to give their corresponding vicinal diols (2 and 4) and alcohols (8 and 10). The stereo-chemistry at the oxymethine carbon was determined based on the long range C–H coupling constants and the modified Mosher's method. Orientation of the adjacent hydroxyl group in (1 and 3) did not affect the enantio-selectivity, whereas the conversion was slightly affected and higher yields were obtained with the R-enantiomers of the α-ketols.