Yuyama (Japan)

Abstract In the present paper we have studied interactions of the N and NH of alkylamines with water. We analyzed the property from the infrared and near-infrared absorptions that hydration causes to tributylamine (TBA) ((Bu)3N) and dibutylamine (DBA) ((Bu)2NH or (Bu)2HN) in the neat liquid or their solutions in heptane at varying concentrations. It has been found that the amine N of TBA very strongly interacts with water and forms the complex (Bu)3N⋯Hb-O-Hf (OHb: bonded OH, OHf: free OH) which is partly dissociated into (Bu)3NH+ and OH− at equilibrium. DBA retains an NH and may act not only as a proton acceptor but also a proton donor to water. Correspondingly, it has been found, the NH is hydrogen-bonded partly through the N to form the strongly-bound complex (Bu)2HN⋯Hb-O-Hf and partly through the H to form the complex (Bu)2NH⋯OH2. From their associated spectral features we propose that the former is partly dissociated into (Bu)2NH2+ and OH− at equilibrium as in the case of TBA and the latter is rather stabilized to be a larger cluster such as (Bu)2NH⋯OH2·(H2O)m.

Abstract The aim of the present study is to investigate how F substitution influences the hydrogen-bonding of the CH to water of an alkane. For this purpose we have comparatively studied the hydrogen bonding of the CH to water of heptane CH3(CH2)5CH3 and 1-fluoroheptane CH2F(CH2)5CH3. The property was analyzed from the separated OH stretching spectra of water dissolved in neat liquids and 1-fluoroheptane solution in heptane as solvent. It has been found that the CH of heptane does not interact with water but the CH of 1-fluoroheptane is hydrogen-bonded as a proton donor to water in the manner of CH⋯OH2. The hydration pattern was supported by the observed effects of hydration on the overtone and combination bands of the CH vibrations of CHCl3, of which the CH acts as a proton donor to water. The present study has spectroscopically shown that the CH, which can be activated by the substitution at the Cα position, of an aliphatic hydrocarbon chain may contribute to the hydrogen-bonding interactions with water in organic and biological materials.

First, we developed quantitative analytical methods of water in poly(methyl methacrylate) (PMMA) in various hydrated states by utilizing the first combination and OH stretching bands of water at about 5240 and 3630 cm-1, respectively. Next, we investigated how the state of water depended on its quantity or the mole ratio of water to the CO (denoted as the H2O/CO ratio), which only interacts with water in PMMA, mainly on the basis of the band feature of the OH stretching bands. Below the H2O/CO ratio of 0.032, the contained water, which shows two clear bands at about 3630 and 3550 cm-1, is hydrogen-bonded to two C=O groups as C=O::H-O-H::O=C to form "the hydration core". The spectrum of the water that exceeds the ratio in question shows one broader band only, the frequency of which shifts downward with the increasing hydration. From detailed analysis of the behavior of the OH stretching and combination bands in relation to the H2O/CO ratio, we have concluded that the water that exceeds the hydration ratio becomes mobile to aggregate or "cluster" around hydrated sites rather than nonhydrated ones in the PMMA matrix, although the latter is much larger in population.