Pressure effects on the complexes of cobalt (II) chloride and cobalt (II) bromide in acetone solution

The acetone solutions of cobalt(II) chloride and cobalt(II) bromide are blue under atmospheric pressure at room temperature and in both of them the main species is tetrahedrally coordinated CoX_2(Ac)_2, where Ac denotes an acetone molecule and X is Cl or Br. The visible absorption spectra of cobalt(II) chloride and cobalt(II) bromide in acetone solution measured under pressures up to 8, 000kg/cm^2 at room temperature showed that the following two kinds of equilibria coexist : CoX_2(Ac)_2 + 4Ac ⇌ Co(Ac)_6^2^+ + 2X^-, (I) CoX_2(Ac)_2 + X^- + ⇌ CoX_3(Ac)^- + Ac. (II) The value of ΔV_1, the volume change of equilibrium (I), is large with the negative sign and changes greatly with increasing pressure. |ΔV_2|, the absolute value of the volume change of equilibrium (II), is small and scarcely depends on pressure. These experimental results indicate the nature of equilibrium (I) and eqilibrium (II): in equilibrium (I) the ionic species are formed and the coordination number increases by the shift to the right side, and in equilibrium (II) there is no change in the number of the charged species and in the coordination number on both sides. In addition, ΔV_1 was estimated from the change of the intrinsic volume, the free volume and the effect of electrostriction

The reaction of nitrile with α-hydrogens under high pressure I : dimerization and trimerization of malononitrile

The effects of pressure on the reaction of malononitrile have been studied in water, methanol, ethanol, iso-propanol, dioxane, and so on in the temperature range of 323 to 343 K up to 8000 kg cm^-2. The reaction produced a dimer and two trimers only at high pressure. The dimer was identified as 1, 1, 3-tricyano-2-amino-1-propene and the trimers as 2, 4-diamino-3, 5-dicyano-6-cyanomethylpyridine, and ammonium 1, 1, 3, 3-tetracyano-2-cyanomethylpropenide, which are, respectively, the "Trimer 1" and "Trimer 2" reported by Schenck and Finken. The "Trimer 3" was not yielded.1. 3, 5-Tricyanomethyl-s-triazine was not produced in the present reaction either. The polar solvents and the addition of triethylamine increased the reaction rate remarkably. The formation of the dimer is autocatalytic and its mechanism is found to be a Thorpe-type reaction

A three-component monooxygenase from Rhodococcus wratislaviensis may expand industrial applications of bacterial enzymes

地球外有機化合物に対する微生物代謝の解明から全く新規な酵素系を発見 --生命分子進化の理解や産業応用に期待--. 京都大学プレスリリース. 2021-01-20.The high-valent iron-oxo species formed in the non-heme diiron enzymes have high oxidative reactivity and catalyze difficult chemical reactions. Although the hydroxylation of inert methyl groups is an industrially promising reaction, utilizing non-heme diiron enzymes as such a biocatalyst has been difficult. Here we show a three-component monooxygenase system for the selective terminal hydroxylation of α-aminoisobutyric acid (Aib) into α-methyl-D-serine. It consists of the hydroxylase component, AibH1H2, and the electron transfer component. Aib hydroxylation is the initial step of Aib catabolism in Rhodococcus wratislaviensis C31-06, which has been fully elucidated through a proteome analysis. The crystal structure analysis revealed that AibH1H2 forms a heterotetramer of two amidohydrolase superfamily proteins, of which AibHm2 is a non-heme diiron protein and functions as a catalytic subunit. The Aib monooxygenase was demonstrated to be a promising biocatalyst that is suitable for bioprocesses in which the inert C–H bond in methyl groups need to be activated

High pressure and high temperature reactions in the organic solid state : polymerization of nitriles

Under the extreme conditions at high pressures up to 50 kbar and high temperatures up to about 300℃, dinitriles, such as malononitrile and succinonitrile, are polymerized to give long chain C, N conjugated polymers with the backbone structure : (-C__1=N-)_n. It is shown that high pressure is necessary in conjunction with high temperature to achieve the polymerization. The minimum pressure and temperature to cause the reaction for malononitrile and succinonitrile are 20 kbar, 160℃ and 25 kbar, 200℃, respectively. The product polymers are beat-resistant and soluble only in dimethylformamide and exhibit semiconducting properties. The mechanism of the reaction can be considered in comparison with the thermal reactions of polyacrylonitrile. The reaction rates were measured. On the other hand, aromatic dinitriles, such as isophthalonitrile and terephthalonitrile, are polymerized only in the presence of HPO_3 as catalyst at 40 kbar and 450℃. The thermal reactions of polyacrylonitrile and polymethacrylonitrile, accompanying the polymerization of cyanide groups, were carried out under such extreme conditions. The naphthyridine type product obtained from polyacrylonitrile under high pressure has higher density, which is ascribable to the formation of a crosslinking network structure. The reaction mechanisms of the lower temperature reaction and the higher temperature reaction of polyacrylonitrile under high pressure were studied. In the case of polymethacrylonitrile, the analogous reaction proceeds only slightly even at 300℃ under 30 kbar. By investigating the effect of water on these reations it was found that the polymerization of dinitriles is accelerated and that polyacrylonitrile and polymethacrylonitrile are easily hydrolyzed to give corresponding polyamides

Effects of pressure on the electrical properties of organic semiconductors : pyrolyzed polyacrylonitrile and α, α-diphenyl-β-picrylhydrazyl

The electrical resistivity of PAN obtained at various pyrolysis temperatures and applied pressures and of DPPH obtained by the crystallization from various solvents were measured under high pressures up to 70 kbar by using a compact cubic anvil apparatus. Its temperature dependence which follows the usual exponential law was also measured to obtain the activation energy for conduction. From these values the carrier mobility under high pressure was estimated. The conduction mechanism was also investigated. The contribution of lone-pair electrons must be taken into account for these substances under consideration in addition to the mobile free π electrons

High-pressure melting in polyethylene

The melting point of polyethylene has been determined at high pressures up to 30, 000 atm by the volume-discontinuity method and differential thermal analysis. The effect of increasing the pressure up to 5, 000 atm is to reduce the volume of fusion. Suitable values for the parameters of the Simon equation, a and c, have been obtained from the melting curve

Effect of pressure on the electrical conductivity of organic substances : I. Pyrolyzed polyacrylonitrile

The electrical conductivity of pyrolyzed polyacrylonitrile has been measured at 15°～100℃, and at pressures up to 50 kb, by the use of a compact cubic anvil apparatus. The conductivity increases markedly with increasing pressure at constant temperature and with increasing temperature at constant pressure. It seems to be closely associated with the amount of π-electron overlap between adjacent molecules. The conductivity under pressure follows the usual exponential law; σ=σ_0exp(-E/kT). The mechanism of pyrolysis has been also investigated

Effect of pressure on the electrical conductivity of organic substances : II. Α, α'-diphenyl-β-picryl hydrazyl

The electrical conductivity of α, α'-diphenyl-β-picryl hydrazyl has been measured at temperatures of 15°～100℃, at pressures up to 70kb by the use of a compact cubic type anvil apparatus. A resistivity reduction as high as two orders of magnitude was observed between 30～70kb at room temperature. The resistivity decreases with increasing temperature at constant pressure. The resistivity under pressure follows the usual exponential law ; ρ=1/σ=ρ_0exp(E/kT). The activation energy also decreases with increasing pressure. The effect of pressure on the conduction is discussed

Layer growth of ZnSb phase in the Zn-Sb diffusion couple at high pressure

The kinetics of growth of the ZnSb phase layer in the Zn-Sb system has been investigated with the diffusion couples annealed in the temperature range of 240 to 320℃, under pressures up to 30 kb and for time up to 17 hr. Among all the intermetallic compounds present in the Zn-Sb equilibrium phase diagram, only ZnSb was the product detected in the diffusion zone. Concentrations of zinc in the ZnSb layer were 20-35 at%, which deviated extensively from the equilibrium concentration. Zinc was by far the faster moving species and the pronounced Kirkendall effect was observed. Since the parabolic rate law was obeyed and the Kirkendall markers moved toward the zinc side, it was concluded that volume diffusion controlled the layer growth and occurred by vacancy mechanism. It has been found that pressure affects not only the growth of the ZnSb phase, but also the interface composition; the increase of 8 kb in the applied pressure reduces the rate constant by about 7% and the increase of pressure from 14 to 22 kb decreases by about 7% the concentration of zinc in the ZnSb layer. The apparent activation energies and the activation volumes are 12.1-14.3 kcal/mol in the range of 240-320℃ and 0.9-1.2cm^3/mol in the range of 14-30 kb, respectively. The diffusion coefficients of zinc calculated by using Kidson's method were 10^-9 - 10^-10 cm^2/sec and they were 5-10 times as large as those obtained in the Zn-As system