Seiya Furutaka

Hydrogen bonding of water with aromatic hydrocarbons at high temperature and pressure

Infrared spectra of HDO dissolved in benzene, toluene, ethylbenzene, o-xylene, m-xylene, and mesitylene at 373–473 K and 100 bar have been measured. It is found that the peak positions of the OH bands assigned to monomeric HDO shift to lower wave numbers as ionization energies of the aromatic compounds decrease. It is concluded that the interaction of water and aromatic compounds in the high temperature–pressure mixtures can be described as π-hydrogen bonding as for that in their complexes observed in the low temperature matrices and jet-cooled clusters.

Infrared study of water–benzene mixtures at high temperatures and pressures in the two- and one-phase regions

Infrared spectra of water–benzene mixtures have been observed at temperatures and pressures in the 473–648 K and 100–350 bar ranges. The OH stretching band intensities of HDO in the benzene-rich phase in the two-phase region and in the one-phase region were obtained as a function of temperature and pressure. The band intensity, as a measure of water concentration, increases by about three times as the temperature rises from 473 to 523 K, while it is almost independent of pressure in the 100–350 bar range at these temperatures. At higher temperatures, on the contrary, the absorption intensities exhibit remarkable pressure dependence. They increase by an order of magnitude as the pressure increases from 100 to 350 bar. These temperature-pressure dependent changes of water concentration can be properly understood with a phase diagram of the water–benzene mixture. The absolute concentration of water in the benzene-rich phase and in the homogeneous one phase has been estimated from the absorption intensities b...

Infrared study of water in benzene at high temperatures and pressure

Infrared spectra of isotopic mixtures of water dissolved in benzene at temperatures in the 373–533 K range and at constant pressure of 100 bar have been measured. The absorption intensities of the OD and OH stretching bands of HDO increases greatly with increasing temperature, indicating increase in solubility of water in benzene. Furthermore, the band shapes exhibit remarkable temperature dependence. This is due to increase in hydrogen bonded species relative to a monomeric species with increasing temperature. Concentrations of HDO in benzene have been estimated from the observed intensities by use of empirical relationships between molar absorption intensities and band peak wave numbers for hydrogen-bonded HDO. The result indicates that the solubility of water in benzene at 533 K and 100 bar is about 40 times larger than that at 293 K and 1 bar. The major part of the hydrogen-bonded species are attributed to dimeric species from comparison of the peak wave numbers of component bands with those reported ...

π- hydrogen bonding between water and aromatic hydrocarbons at high temperatures and pressures

Infrared OH stretching absorption of HDO isolated in aromatic hydrocarbons have been measured at temperatures of 473 and 523 K and at pressures in the 100–350 bar range. The peak frequencies are dependent on the solvents and their order, benzene>toluene>ethylbenzene>cumene>o-xylene∼m-xylene>mesitylene, is exactly the same as the order for the ionization potentials of the hydrocarbons. Shifts of the frequencies from that of HDO in hexane, which was measured as a reference at the same temperature and pressure, were analyzed using a charge transfer theory for hydrogen bonding. Distances between the water molecule and a solvent phenyl ring were estimated to be 2.8±0.1 and 2.9±0.1 A at 473 and 523 K, respectively. These values are consistent with a structure of a water–benzene complex determined by a jet-cooled microwave spectroscopy. These facts suggest that the π-hydrogen bond between water and aromatic hydrocarbons exists even at the high temperatures under pressure.

Infrared study of anomalous volume behavior of water–benzene mixtures in the vicinity of the critical region

Volume behavior of water–benzene mixtures at temperatures and pressures in the 473–623 K and 100–350 bar ranges, respectively, has been studied by infrared in situ measurements. The densities of the benzene-rich phase were estimated from the spectroscopically determined concentrations of water and benzene and compared with the average densities before mixing, which were calculated using literature densities of neat water and neat benzene at the same temperature and pressure. Anomalously large volume change for mixing has been found in the vicinity of the critical region of the water–benzene mixtures.

Anomalous volumetric behavior of water-hexane and water-decane mixtures in the vicinity of the critical region as studied by infrared spectroscopy

Infrared spectra of binary mixtures of water with hexane and decane were measured at temperatures and pressures in the 473-648 K and 70-350 bar ranges, respectively. Volumetric concentrations of water and the hydrocarbons in the mixtures were obtained from absorption intensities of the fundamental OH stretching band of HDO and combination transitions of the hydrocarbons. Using both the concentrations, densities of the aqueous mixtures were estimated and compared with densities before mixing, which were calculated using literature densities of the neat liquids. It is found that anomalously large volume expansion on mixing occurs in the vicinity of the critical region of the mixtures.

Infrared study of water–benzene mixtures at high temperatures and pressures

Infrared spectra of water–benzene mixtures have been measured at temperatures and pressures in the 473–648 K and 100–350 bar ranges, which extend over the two- and one-phase regions of the mixtures. Molar concentrations of water and benzene in the benzene-rich phase were estimated from absorption intensities of the OH stretching band of HDO and combination bands of benzene, respectively. Using these results, densities of the benzene-rich phase were estimated and compared with the average densities before mixing which were calculated from literature densities of the neat liquids at the same temperature and pressure. An anomalously large volume change for mixing has been found in the vicinity of the critical region of the mixture.