A family of pairs of imaginary cyclic fields of degree $$(p-1)/2$$(p-1)/2 with both class numbers divisible by p

The Ramanujan Journal - Let p be a prime number with $$p\equiv 5\ (\mathrm{mod}\ {8})$$. We construct a new infinite family of pairs of imaginary cyclic fields of degree $$(p-1)/2$$ with both class...     

Effect of solution pH on complex formation between epi-type catechin and β-cyclodextrin

Journal of Thermal Analysis and Calorimetry - The effect of solution pH on the formation of an inclusion complex between (?)-epigallocatechin gallate (EGCg: pKa?=?7.5) and...     

Speciation of dissolved silicates in natural waters containing alkaline and alkaline-earth ions

The concentration of silica in water samples from the desert area of Xinjiang, N. W. China, has been measured by colorimetry with ammonium molybdate. The observed pattern of dependence of the concentration of silica on the concentration of sodium ion (Na⁺) in the water samples is consistent with the pattern obtained by experiments on in-vitro dissolution of silica gel in sodium chloride (NaCl) solution. This indicates that the dissolution of silica in the hydrologic system in this area depends on the concentration of Na⁺. Calcium ion (Ca²⁺), which is known to play an important role on the dissolution of silica on the basis of in-vitro experiments, was observed to take little part in the dissolution of silica in actual natural water samples. This implies that the Ca²⁺ is bound to the hydrogen carbonate anion or that the Ca²⁺ content of natural water containing salts is very low, owing to precipitation. In these samples silicate-Na⁺ was identified as the dissolution species of silica; it was also ascertained that Ca²⁺ did not form complexes with silicate species. These observations resulted from direct identification of dissolved chemical species by use of FAB-MS (fast atom bombardment mass spectrometry). The research indicates that in water samples in this critically arid region the concentration of dissolved silica is basically determined by the concentration of Na⁺, indicative of pure inorganic conditions in the desert area of Xinjiang, N.W. China.     

Visible light sensitive cyclomer and its tautomeric dispiro compound formed from bispyridinyl diradical

Two-electron reduction of 4,4'-(1,5-pentanediyl)bis(N-methylpyridinium) (52+) with sodium amalgam in degassed acetonitrile leads quantitatively to the formation of a cyclomer of 3,15-dimethyl-3,15-diazatricyclo[10.3.1.12,6]heptadeca-4,6(16),12(17),13-tetraene (6) by intramolecular cyclization. In degassed acetonitrile, 6 is stable for a long time at room temperature and, hence, a highly stable species. In contrast, 6 undergoes a photochemical reaction to give its valence tautomer having a dispiro structure, 3,10-dimethyl-3,10-diazadispiro[5.0.5.5]heptadeca-1,4,8,11-tetraene (7), when irradiated with visible light shorter than 450 nm. Noteworthy is the experimental fact that 7 is unstable to heat and, hence, reverts back to 6 by application of heat.     

Long branching in poly(vinyl acetate) and poly(vinyl alcohol). I. Crosslinking and crosslinking cleavage of poly(vinyl acetate)

A crosslinked network was formed by the reaction of partially saponified poly(vinyl acetate) and toluylene diisocyanate in benzene. The yield of gel was markedly dependent on the degree of saponification and the concentrations of polymer and diisocyanate. Crosslinked poly(vinyl alcohol) was obtained by treating the poly(vinyl acetate) with a catalytic amount of sodium hydroxide in methanol without any change of the urethane crosslinks. The crosslink based on the urethane linkage was quantitatively cleaved by acids, especially by hydrobromic acid, releasing polymers of the same molecular weight as the original.     

The preparation of trichlorotris(hydrogen-salicylato)rhodate(III) and tetra-μ-(hydrogen-salicylato)diaquadirhodium(II)

The preparation of a new example of a salicylato divalent rhodium complex, namely, tetra--(Hsal)diaquadirhodium(II), and a new trivalent complex, the trichlorotris(Hsal)rhodium(III) ion are reported. The complexes were isolated and characterized by spectrochemical methods including FT-Raman and n.m.r. spectroscopies. The trivalent complex has a monodentate Hsal ligand bonded through a carboxyl oxygen with a facial configuration.     

Optically active coordination compounds---XLVIII. Synthesis, resolution and interconversions of isomers of tris-salicylatocobaltate(III)

Stable aqueous solutions of the green ion [Co(sa1)₃]³⁻ (sa1 = dianion, C₆H₄( )(CO ), of salicylic acid, 2-hydroxybenzoic acid) are obtained from [Co(NH₃)₅ C1]C1₂ and an excess of salicylic acid. Several salts, [C][Co(sa1)₃] have been characterized, where C = [Co(NH₃)₆]³⁺ and [M(en)₃]³⁺ (M = Co or Rh, EN = 1,2-diamino-ethane). By using (+)-[Rh(en)₃]³⁺, optical resolution via less soluble diastereoisomeric salts has been achieved, and isomerization and racemization have been studied. Resolved tris-malonatocobaltate(III) has been used as a model. A novel thermochromism (77-293 K) in solid Δ(+)-[Rhen₃]Λ[Co(sa1)₃ is described.     

Selective transformation of organoboranes to grignard reagents by using pentane-1,5-di(magnesium bromide). Syntheses of the pheromones of southern armyworm moth and Douglas fir tussock moth

The selective transformation of trialkylboranes or B-alkyl-9-borabicyclo[3.3.1]-nonanes to alkylmagnesium bromides was accomplished upon treatment with pentane-1,5-di(magnesium bromide) ($\text{1}$) in benzene.     

Ruthenium catalyzed transformation of alcohols to esters and lactones

Homogeneous catalytic oxidative condensation of alcohols and diols to their corresponding esters and lactones has been accomplished using RuH₂(PPh₃)₄.