Die Verteilung von n-Caprylsäure zwischen organischen Lösungsmitteln und wäßriger Natriumsufatlösung

Es wurde die Verteilung von n-Caprylsäure zwischen n-Decan, Benzen, Isoamylacetat, Diisopropylketon, Isoamylalkohol und einer wäßrigen 0,6 molaren Natriumsulfatlösung unter Einsatz der ¹⁴C-markierten Säure untersucht. Die Verteilungs- und Dimerisationskonstanten für die Reaktionen HR_(w) ? HR_(org) bzw. 2 HR_(org) ? (HR)_2(org) wurden bestimmt. Der Einfluß der Lösungsmittel auf die Verteilung der Säure sowie die Bedeutung derartiger Untersuchungen für die Interpretation von Flüssig-Flüssig-Extraktionsgleichgewichten wird diskutiert.     

Heterometallic cyanide-bridged complexes containing RhRuRh triad: NMR data on exchange reactions and ligand effect transmission

Trans-[RuPy₄(CN)₂ cleaves chloro-rhodium bridges in rhodium(I) binuclear complexes, [Rh(CO)₂Cl]₂, [Rh(Cod)Cl]₂, and [(Cod)RhCl₂Rh(CO)₂] yielding heterometallic triad complexes, [(CO)₂ClRh(NC)RuPy₄(CN)RhCl(CO)₂] (I), [(Cod)ClRh(NC)RuPy₄(CN)RhCl(Cod)] (II), and [(Cod)ClRh(NC)RuPy₄(CN)RhCl(CO)₂] (III), respectively. In solutions, III coexists with equilibrium amounts of I and II in the near-binomial proportions. Under action of [Rh(CO)₂Cl]₂, II transforms into I with parallel formation of [Rh(Cod)Cl]₂. Ligand effect transmission along the L-Rh-NC-Ru-CN-Rh-L′ chain is studied by ¹H and ¹³C NMR. Chemical shifts δ¹H and δ¹³C of Ru-bound Py ligands are sensitive to the nature of Rh-bound ligands. Values of δ¹H and δ¹³C of Cod and ¹³C of CO ligands are sensitive to the ligands at the remote end of the L-Rh-NC-Ru-CN-Rh-L′ chain. Reaction of trans-[RuPy₄(CN)₂] with Rh₂(OAc)₄ yields an apparently linear polymer [-Rh(OAc)₄Rh-NCRuPy₄CN-]. Upon action of [Rh(CO)₂Cl]₂, the polymer decomposes yielding I and Rh₂(OAc)₄. X-ray structure data for I are given.     

cis-trans-and Intramolecular enol-enolic equilibrium of β-ketoaldehydes

Tautomerism of aromatic β-ketoaldehydes p-XPhCOCH₂CHO ( 1 , X = NMe₂, OMe, Me, H, Br, NO₂), aliphatic β-ketoaldehydes and benzoylacetaldehyde RCOCH₂CHO ( 2 , R = Me, i-Bu, t-Bu, Ph), RCOCH(Me)CHO ( 3 , R = Me, Et, i-Pr) and methyl 2-formylpropionate MeOCOCH(Me)CHO ( 4 ) has been studied by the ¹H NMR technique. In basic solvents both cis- and trans-enol forms of these compounds co-exist. trans-Enolisation, which occurs exclusively at the formyl group, is most favoured in compound ( 4 ) and least favoured in compounds ( 1 ) and ( 2 ). The increasing electron-attracting property of the substituent X in the aromatic β-ketoaldehydes ( 1 ), as well as increasing solvent basicity in the series propanediol-1, 2-carbonate, acetone < dimethylformamide < dimethylacetamide < pyridine, also shifts the equilibrium towards the trans-enol form. The trans-enol form is absent in aprotic solvents of low basicity such as CCl₄, C₂HCl₃ and toluene. The thermodynamic parameters of the cis-trans-enol (C ? T) and cis-enol-enolic (C ? C') equilibria have been estimated from the temperature dependences. The transition from the cis-to the trans-enol form is accompanied by an entropy decrease of about 10 cal mol^?1 degree^?1. Nevertheless the trans-enol form is stabilised due to its lower enthalpy. The cis-trans-enol equilibrium is determined by the relative strength of the intramolecular hydrogen bond in the cis-enol form and the intermolecular hydrogen bonds with basic solvent molecules of the trans-enol form. The enthalpy difference of the two cis-enolic forms does not exceed 1.0 kcal/mol, in rough agreement with the data calculated by the CNDO/2 approximation. Polar solvents favour the hydroxymethyleneketone form (C) for both groups of compounds 2 and 3 . The content of the hydroxymethyleneketone form is about the same within series 2 where R = Me, i-Bu, Ph and is a little higher for the t-Bu derivative. A decrease of temperature only slightly shifts the equilibrium of compounds 1 and 2 to the hydroxymethyleneketone form, while in the case of 2-methyl-β-ketoaldehydes (3) this effect is markedly pronounced.     

W–C Electrode Erosion in a Pulsed Arc Submerged in Liquid

Electrode erosion was studied in pulsed arcs ignited between two electrodes comprised of 99.99% C (graphite) and 99.5% W submerged in deionized water or analytical (99.8%) ethanol. In the both cases the erosion rate increased proportionally to the pulse energy, and the total electrode erosion per unit energy was inversely proportional to the discharge pulse duration. Fifteen and sixty-μF discharge capacitors were used for formation of the pulses in water. It was obtained that, respectively (a) erosion of the tungsten anode (W_a) was by factors of 5–6 and ∼10 greater than that of the carbon (C_c) cathode; (b) erosion of the carbon anode (C_a) was by a factor of 1.34 greater and by a factor of 2.65 less than that of the tungsten cathode (W_c); (c) the total erosion rate of both electrodes (anode and cathode) per unit pulse energy for the W_a–C_c pair was greater by factors of 11 and 12.5 than that for the W_c–C_a pair.     

The structure of the lactones α- and β-reolones

Summary 1. Structures have been proposed for - and -reolones (Ia and Ib), two spatial isomers isolated by us previously, as 3,4-dimethyl-2-(4-O-methyl-1--resorcyloyl)-8-oxononan-1,4-olides with the trans-diaxial position of the methine protons in the lactone ring, and with the equatorial orientation of the open chain at C₄ in -reolone and the axial orientation in -reolone.2. The possibility has been found of converting -reolone in an acid medium into a 7-methoxy-4-oxodihydrocoumarin derivative at the 3-carbon atom.V. L. Komarov Botanical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 30–38, January–February, 1977.     

1,3-thiazinediones and pyrimidinediones

The character of the effect of substituents on the position of the keto-enol equilibrium in 2-substituted 4,6-dioxodihydro-1,3-thiazines and the structure of the enol form are examined. 2-Phenyl-4,6-dioxodihydro-¹⁵N-1,3-thiazine was synthesized. It was shown by ¹³C NMR spectroscopy that the 2-phenyl-4-hydroxy-1, 3-thiazin-6-one structure corresponds to the enol form.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 481–484, April, 1979.     

Functional neural network analysis in frontotemporal dementia and Alzheimer's disease using EEG and graph theory

Background  

Although a large body of knowledge about both brain structure and function has been gathered over the last decades, we still have a poor understanding of their exact relationship. Graph theory provides a method to study the relation between network structure and function, and its application to neuroscientific data is an emerging research field. We investigated topological changes in large-scale functional brain networks in patients with Alzheimer's disease (AD) and frontotemporal lobar degeneration (FTLD) by means of graph theoretical analysis of resting-state EEG recordings. EEGs of 20 patients with mild to moderate AD, 15 FTLD patients, and 23 non-demented individuals were recorded in an eyes-closed resting-state. The synchronization likelihood (SL), a measure of functional connectivity, was calculated for each sensor pair in 0.5–4 Hz, 4–8 Hz, 8–10 Hz, 10–13 Hz, 13–30 Hz and 30–45 Hz frequency bands. The resulting connectivity matrices were converted to unweighted graphs, whose structure was characterized with several measures: mean clustering coefficient (local connectivity), characteristic path length (global connectivity) and degree correlation (network 'assortativity'). All results were normalized for network size and compared with random control networks.     

Mathematical model of thermocracking of anisotropic brittle materials

A mathematical model of the process of laser-co ntrolled thermocracking for thin plates of aniso-tropic elastic materials has been constructed. By means of sequential replacement of the variable scale along one of the orthogonal coordinates, the problem of determination of the potential has been reduced to the Poisson equation. A comparison with the experiment by the example of thermocracking of a single-crystal quartz plate in a circumferential direction has been carried out.