Keizo Suzuki

Near-infrared spectra of water and aqueous electrolyte solutions at high pressures

The near-infrared spectra (9500 to 11000 cm−1) of pure water and aqueous solutions of alkali halides, MgCl2, NaClO4, and R4NBr were measured at temperatures between 10 and 55°C and pressures up to 500 MPa. From the analysis of the absorption spectra the following conclusions are drawn. (1) The ice I-like open structure is destroyed and the packed structure is formed as the pressure is increased. (2) The open structure of water is destroyed by the addition of alkali halides and MgCl2 and water molecules are restricted around the ions by ion-dipole interactions. This results in a loosening of the O−H bond. (3) The perchlorate ion destroys the open structure of water and the ion-dipole interaction with water is insignificant. (4) The Bu4N+ ion forms water structure around the ion similar to that of the clathrate open structure.

Effect of pressure on the solubilities of LiF, NaF, KCl, NH4, Cl, K2SO4, (NH4)2SO4, and ZnSO4·7H2O in water at 298.15 K

Abstract Solubilities of seven inorganic compounds in water were measured at 298.15 K and up to 350 MPa. The solubilities of K2SO4, LiF, NaF, and KCI increased with increasing pressure, those of NH4Cl and (NH4)2SO4 decreased, and that of ZnSO4·7H2O showed almost no dependence on pressure. From the slopes of these solubility curves at 0.1 MPa, we estimated the volume changes accompanying the dissolution of the solutes. These values coincided with the volume differences between the partial molar volume at saturation and the molar volume of the crystal within ca. ± 1 cm3 mol−.

Effect of pressure on the solubilities ofo-,m- andp-xylene in water

The solubilities of o-, m- and p-xylene in water were measured at 25.0°C up to 250, 385, and 50 MPa, respectively. The solubility increased with increasing pressure up to 120 MPa (50 MPa for p-xylene) and then decreased. The reaction volumes, ΔVo accompanying the dissolution at 0.1 MPa were estimated as −3.6±0.5, −3.4±0.5, and −4.1±0.5 cm3-mol−1 for o-, m-, and p-xylene, respectively, from the pressure dependences of the solubilities. The limiting partial molar volumes, of p- and o-xylene in water under high pressure were estimated from ΔVo and the molar volume of the xylene. The partial molar volumes decreased with increasing pressure. The reaction volume for the formation of intra-molecular pairwise hydrophobic interaction between the methyl groups, as proposed by Ben-Naim, is discussed for the ΔVo of p- and o-xylene at 0.1 MPa.

The effect of pressure on the cloud point of aqueous polymer solutions

Abstract The effect of pressure on the cloud point of aqueous polymer solutions, such as poly(methacrylic acid) (PMA), poly(propylene glycol) (PPG), partially butyrated poly(vinyl alcohol) (PVA-Bu), and copolymer(vinyl pyrrolidone-vinyl acetate) (PVP-VAc) were studied to clarify what kind of intermolecular forces contribute to the dissolution process of these polymers in water. The values of ΔH0 and ΔV0 accompanying the dissolution process were calculated from the equations, [∂ ln c/∂(1/T)]P ∝ - ΔH0/R, and (∂ ln c/∂P)T ∝ -ΔV0/RT, respectively. The process is first characterized by the negative value of ΔH0 in every case. Secondly, the process is classified into three types according to the signs of ΔV0 as follows: (a) ΔV0 ΔV 0 ≷ 0 (the ΔV0 value changes the sign from negative to positive at about 3000–4000 atm); PPG, (c) ΔV0 > 0; PVA-Bu and PVP-VAc. From the signs of these thermodynamic quantities, the dissolution process of each type is discussed in the terms of the intermolecular forces.

Effects of temperature and pressure on the near-infrared spectra of HOD in D2O

The near-infrared absorption spectra (9500 to 11000 cm−1) of HOD, 20 mol% in D2O were measured at temperatures between 4 and 55°C and pressures up to 500 MPa. From the analysis of the spectra, the following conclusions are drawn. (1) At temperatures below about 38°C, the ice I-like bulky structure is destroyed to form the dense structure which reflects the high-pressure ice-like structure as the pressure is increased. (2) At temperatures above about 38°C, the bulky structure hardly remains at atmospheric pressure and the formation of dense structure proceeds monotonically with increasing pressure. The results and conclusion obtained in the present paper agrees with those obtained for pure H2O water in the previous investigation.

Effect of pressure on the dimerization of benzoic acid in n-heptane

Abstract Ultraviolet absorption spectra of benzoic acid in n -heptane were measured at 25°C and up to 640 MPa. The reaction volume for the cyclic dimerization of benzoic acid was estimated as 0.4 ±0.9 cm 3 mol −1 from the pressure dependence of the dimerization constant. This is much more positive than those for noncylic hydrogen-bond formations which are from −3 to −6 cm 3 mol −1 . It is ascribed to a compensation between a reduction in the volume accompanying the hydrogen-bond formation and an increase accompanying the cyclization. These two contributions to the reaction volume are estimated quantitatively.

Effect of pressure on the dynamics of nitrate anions in aqueous solutions

Abstract The Raman spectra of the totally symmetric ν 1 (A 1 ′) 1050 cm −1 mode of a NO 3 − ion have been studied in 2M LiNO 3 , NaNO 3 , and KNO 3 aqueous solutions up to 2 kbar at 25°C. The vibrational G v ( t ) and rotational G r ( t ) correlation functions have been calculated from the Fourier transform of the isotropic and anisotropic Raman profiles at various pressures. We cannot observe any pressure effects on G v ( t ), but can observe a large pressure effect on G r ( t ). G r ( t ) decays more slowly with pressure, except for Li + at 2.0 kbar. The slower decay of G r ( t ) under pressure indicates that the rotational motion of a NO 3 − ion is restricted through the hydrogen bonding between the NO − 3 ion and water molecules. The rotational relaxation time is also calculated from the Raman line widths. From the hydrodynamic theory between the relaxation time and the viscosity of the solution, the rotational diffusion of a NO 3 − ion under pressure corresponds to a stick boundary condition.

Pressure dependence of NMR spectroscopy for studying intermolecular interactions 1H NMR in organic solvents involving the nitroxide radical

Abstract Pressure effects on 1 H chemical shifts and relaxation rates in organic solvents containing the nitroxide radical have been observed. 1 H chemical shifts with pressure and pressure-broadenings for hydrogen bonding between proton-donor molecules and the nitroxide radical have been observed.

Early Days of Pressure Denaturation Studies of Proteins

The denaturation of protein by pressure has been generally well known since the findings of the perfect coagulation of egg white by a pressure of 7,000xa0atm within 30xa0min by Bridgman (J Biol Chem 19:511-512, 1914), and Kiyama and Yanagimoto (Rev Phys Chem Jpn 21:41-43, 1951) confirmed that the coagulation occurs above 3,880xa0kgxa0cm(-2). Grant et al. (Science 94:616, 1941) and Suzuki and Kitamura (Abstracts of 30th annual meeting of Japanese Biochemical Society, 1957) found that SH groups are detected at the compressed sample of ovalbumin. On the other hand, Johnson and Campbell (J Cell Comp Physiol 26:43-49, 1945), Tongur (Kolloid Zhur 11:274-279, 1949; Biokhimiya 17:495-503, 1952) and Suzuki et al. (Mem Res Inst Sci Eng Ritsumeikan Univ 3:1-4, 1958) reported that the thermal denaturation of proteins is retarded in a few examples by the low pressure of about 1,000xa0atm. Before 1960, the studies of denaturation under high pressure were, however, rare and almost qualitative compared with those by heat, acid, urea and so on, so that there was no theory for the influence of hydrostatic pressure on the mechanism of denaturation. Here I review how I started experiments and analysis on pressure denaturation of proteins in early days of 1950s and 1960s in my laboratory and others.

Effect of Pressure on the Hydrogen-Bond Formation between Phenol as a Proton Donor and Three Ethers in N-hexane

Abstract The effect of pressure on the hydrogen (H)-bond formation between phenol as a proton donor and three simple aliphatic ethers as proton acceptors in n -hexane was studied by means of UV absorption spectroscopy up to 640 MPa at 25°C. The reaction volumes for H-bond formation were -6.1 cm 3 mol −1 for diethyl-, -6.4 cm 3 mol −1 for di- n -propyl-, and -5.1 cm 3 mol −1 for di- n -butyl ether, respectively. They show that the reaction volume for H-bond formation between phenol and aliphatic ether is about -6 cm 3 mol −1 without depending on the length of the substituents of a proton donor.