The water structure and proton conductance at high pressure (Modern aspects of physical chemistry at high pressure : the 50th commemorative volume)

Recent advances in studies of water and proton conductance at high pressure are reviewed with the following contents. 1. Introduction 2. Water at high pressure 2-1. Phase diagram (water and ices) 2-2. P-V-T Relation 2-3. Spectroscopic and dielectric properties 2-4. Transport and relaxation phenomena 2-5. Properties of computer-simulated water 3. Proton conductance at high pressur

Pressure effects on fluorescence and photodimerization of anthracene and 9-methylanthracene in solution

The relative values of photodimerization yields Φ. and fluorescence yields Φ_f with anthracene and 9-methylanthracene were measured in n-hexane at room temperature under pressures up to 3, 000kg/cm^2. In anthracene where Φ_f has a slight pressure dependence, the apparent first order rate constant k_o_b_s for photodimerization yield was approximately inversely proportinal to the viscosity of the solvent. On the other hand, in 9-methylanthrareae where Φ_f increases steeply with increasing pressure, k_o_b_s did not decrease with pressure so much as predicted from the increase of the viscosity of the solvent. Considering the changes of Φ_f as the changes of lifetime. τ_f of the lowest excited singlet state S_1, the pressure dependences of photodimerization rate constants k_r were obtained according to the relation k_o_b_s = k_r.τ_f. In 9-methylanthracene as well as anthracene k_r were nearly inversely proportional to the viscosity of the solvent. The remarkable effects of pressure on fluorescence yields also were discussed in view of the intersystem crossing from the S_1 state to the second triplet state T_2

Studies on explosion limits of butadiene-air mixture

The explosion limits of butadiene-air mixtures were determined by means of the admission method and the reaction products, analyzed by gas-chromatography, were CO, CO_2, H_2O, C_2H_4, HCHO etc. The isochor curves show that the lowest butadiene composition of explosion is 20vol % and the explosion peninsula are found at 2～3 vol % of butadiene, under at 25 cmHg of pressure. The isobar and isotherm curves show U type. The reaction can be explained on the thermal explosion theory and the apparent activation energy is estimated to be about 32～34 kcal/mol at 2～30vol % of butadiene. The reaction consists of oxidation, and polymerization

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

The protein denaturation under high pressure : effects of ph and some substances on the pressure denaturation of ovalbumin solution

The effects of the pH and of the various added substances on the pressure denaturation of ovalbumin solution were examined by measuring the solubility as an index. The results are as follows: Ovalbumin has the maximum stability near pH 9 toward pressure-denaturation, the rate of pressure denaturation reaction of ovalbumin is proportional to the square root of hydrogen-ion concentration independently of the treated pressure and temperature, and the activation volumes are negative and the values depend on temperature but not on pH. Sulfate and glucose are inhibitors, and urea and ethyl alcohol are accelerators for pressure denaturation. And a little amount of calcium chloride and sodium chloride accelerates the pressure denaturation, but a large amount of them tend to inhibit it