72 research outputs found
Thermodynamics of Mixtures Containing Amines. XV. Liquid–Liquid Equilibria for Benzylamine + CH3(CH2)nCH3 (n = 8, 9, 10, 12, 14)
Coexistence curves for the liquid−liquid equilibria (LLE) of 1-phenylmethanamine
(benzylamine) + CH3(CH2)nCH3 (n = 8, 9, 10, 12, 14) have been
determined using the critical opalescence method by means of a laser scattering technique.
All of the LLE curves show an upper critical solution temperature (UCST), which increases
with increasing n. For systems including a given n-alkane, the UCST decreases in the
sequence aniline > 2-methylaniline (o-toluidine) > benzylamine > N-methylaniline >
pyridine. This means that amine−amine interactions become weaker in the same order.
Most of the DISQUAC interaction parameters for the aliphatic/amine (a,n) and aromatic/
amine (b,n) contacts previously determined for solutions with aniline, o-toluidine, or
N-methylaniline have been used for the representation of the LLE data. Only the first
dispersive interaction parameter of the (a,n) contact has been modified. The coordinates of
the critical points are correctly represented by the model
Orientational Effects and Random Mixing in 1-Alkanol + Alkanone Mixtures
1-Alkanol + alkanone systems have been investigated through the data analysis of molar excess functions,
enthalpies, isobaric heat capacities, volumes and entropies, and using the Flory model and the formalism of the concentrationconcentration
structure factor (SCC(0)). The enthalpy of the hydroxyl-carbonyl interactions has been evaluated. These
interactions are stronger in mixtures with shorter alcohols (methanol-1-butanol) and 2-propanone or 2-butanone. However,
effects related to the self-association of alcohols and to solvation between unlike molecules are of minor importance when
compared with those which arise from dipolar interactions. Physical interactions are more relevant in mixtures with longer
1-alkanols. The studied systems are characterized by large structural effects. The variation of the molar excess enthalpy with the
alcohol size along systems with a given ketone or with the alkanone size in solutions with a given alcohol are discussed in terms of
the different contributions to this excess function. Mixtures with methanol show rather large orientational effects. The random
mixing hypothesis is attained to a large extent for mixtures with 1-alkanols ≠ methanol and 2-alkanones. Steric effects and
cyclization lead to stronger orientational effects in mixtures with 3-pentanone, 4-heptanone, or cyclohexanone. The increase of
temperature weakens orientational effects. Results from SCC(0) calculations show that homocoordination is predominant and
support conclusions obtained from the Flory model.Ministerio de Ciencia e Innovación, under Project
FIS2010-1695
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
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