Deuterium Isotope Effects on Miscibility Curves of Nitromethane + Pentanol and Nitromethane + Isobutanol

Abstract

The miscibility of nitromethane with pentanol and isobutanol and the influence of deuterium substitution over a broad concentration range have been reported. The miscibility results enable the construction of the phase diagrams for eight systems. It appears that deuteration both in the OH group of alcohol and/or the methyl group of nitromethane increases the domain of the limited miscibility, and the isotope shift of the upper critical solution temperature ranges from 0.15 K for deuterated alcohols to 1.38 K for deuterated nitromethane + regular isobutanol system. The phase diagrams can be described by using a scaling equation with a critical exponent β close to the predicted one and practically independent of the isotope substitution. The good description of the system was also obtained by using the classical equations based on the mean-field theory.

Densities, Viscosities, and Speeds of Sound of the Nitromethane + 1-Pentanol System near the Critical Demixing Temperature: Effect of Deuterium Substitution

“…The same trend is observed for pentanol. Viscosity isotope effects agree well with those reported by Rabinovich 7 and Holz et al 8 The isotope substitution does not affect the kinematic viscosity of nitromethane significantly, and the resulting isotope effect on the dynamic viscosity is primarily due to the isotope effect on density. Thus, the viscous flow is almost independent of deuterium substitution.…”

“…Among them are molar volumes (V m ), The results obtained presently agree satisfactorily well with previously reported data (Table 3). Table 4 summarizes the isotope effects on several thermodynamic properties studied for selected temperature 303 K. Whenever possible, we include for comparison the results obtained by Rabinovich 7 and Holz et al 8 As can be seen in those few possible cases, the results presently obtained agree well with those reported in the literature except for the values of the isotope effect on the isobaric thermal expansivity. Here, a significant disagreement should be mentioned.…”

“…The isotope effects on the molar volume are very close to the literature values. From a qualitative perspective, the observed sign of the isotope effect on the molar volume is as predicted . A simple core-size analysis tells us that the molecular volume of nitromethane- h 3 is expected to be slightly greater than that of nitromethane- d 3 because anharmonicity, combined with higher internal vibrational frequencies for the lighter molecule, leads to greater vibrational amplitudes of the C−H stretching modes compared to those of the C−D modes.…”

“…From a qualitative perspective, the observed sign of the isotope effect on the molar volume is as predicted. 7 A simple coresize analysis tells us that the molecular volume of nitromethane-h 3 is expected to be slightly greater than that of nitromethane-d 3 because anharmonicity, combined with higher internal vibrational frequencies for the lighter molecule, leads to greater vibrational amplitudes of the C-H stretching modes compared to those of the C-D modes. However, the isotope effect on the mass density is basically a consequence of the molar mass difference between isotopomers (nitromethane-h 3 , 61.04 × 10 -3 kg‚mol -1 ; nitromethane-d 3 , 64.06 × 10 -3 kg‚mol -1 ).…”

Two ways of looking at Prigogine and Defay's equationElectronic supplementary information (ESI) available: Sources of vE(x,T) and hE(x,T) data. See http://www.rsc.org/suppdata/cp/b2/b200292b/

“…Temperatures at which excess properties have been determined were chosen from knowledge of the critical temperatures at nominal null pressure. Table 2 reports previously determined critical compositions and temperatures, and compares, for the latter case, values taken from the literature [21][22][23][24][25][26][27][28][29][30] with ours at nominal null pressure. Tables 3 and 4 report our experimental data of quasicritical (T,p) isopleths and excess properties at near-critical temperatures, respectively.…”