Orientational Effects and Random Mixing in 1‑Alkanol + Nitrile Mixtures

1-Alkanol + alkanenitrile or + benzonitrile systems have been investigated by means of the molar excess functionsenthalpies (Hm E ), isobaric heat capacities (Cp,m E ), volumes (Vm E ), and entropiesand using the Flory model and the concentration−concentration structure factor (SCC(0)) formalism. From the analysis of the experimental data available in the literature, it is concluded that interactions are mainly of dipolar type. In addition, large Hm E values contrast with rather low Vm E values, indicating the existence of strong structural effects. Hm E measurements have been used to evaluate the enthalpy of the hydroxyl−nitrile interactions (ΔHOH−CN). They are stronger in methanol systems and become weaker when the alcohol size increases. In solutions with a given short chain 1-alkanol (up to 1-butanol), the replacement of ethanenitrile by butanenitrile weakens the mentioned interactions. Application of the Flory model shows that orientational effects exist in methanol or 1- nonanol, or 1-decanol + ethanenitrile mixtures. In the former solution, this is due to the existence of interactions between unlike molecules. For mixtures including 1-nonanol or 1-decanol, the systems at 298.15 K are close to their UCST (upper critical solution temperature), and interactions between like molecules are dominant. Orientational effects also are encountered in methanol or ethanol + butanenitrile mixtures because self-association of the alcohol plays a more important role. Aromaticity effect seems to enhance orientational effects. For the remainder of the systems under consideration, the random mixing hypothesis is attained to a rather large extent. Results from the application of the SCC(0) formalism show that homocoordination is the dominant trend in the investigated solutions, and are consistent with those obtained from the Flory model

Dielectric relaxation study of some schiff bases derived from 2-hydroxy-5-chloroacetophenone and <i>p</i>-substituted anilines in methanol solutions

1011-1012Static permittivities and relaxation times have been determined for five schiff bases derived from 2-hydroxy-5chloroacetophenone and p-substituted aniline in methanol solution by using a time domain reflectometry (TDR) technique. The static permittivity decreases slightly with increase in mole concentration of the compounds in methanol. All systems can be described by the Oebye relaxation times. The study shows that the compounds do not affect the dielectric properties of methanol significantly. This suggests that the hydrogen bonding in methanol remains unaffected by these agents at the concentrations considered in the paper

Dielectric study of electrolyte: Ca(NO₃)₂·4H₂O in aqueous solution of urea

878-883The time domain reflectometry is used to determine the permittivity parameters of Ca(NO3)24H2O in aqueous solution of urea at different temperatures. A calibration procedure based on least squares fit method is used. It is found that the values of static dielectric constants increase with increase of the salt and urea in water. The dielectric as well as conductivity data suggest incomplete dissociation of the salt in the solution