Vapor phase association of methanol. Vapor density evidence for trimer formation

Christian, Sherril D.; Cheam, Venghuot; Farnham, Sutton B.

doi:10.1021/j100717a027

Cited by 18 publications

(2 citation statements)

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“…( 4) gives unsatisfactory prediction for liquids like water and methanol. Like water, the last is known of its associative properties [17,18].…”

Section: Table Imentioning

confidence: 99%

Surprising properties of water on its binodal as the reflection of the specificity of intermolecular interactions

Kulinskii,

Malomuzh

2009

Preprint

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In the paper the behavior of density (or specific volume), the heat of evaporation and entropy per molecule for normal and heavy water on their coexistence curves is discussed. The special attention is paid on the physical nature of the similarity in the behavior of density and the heat of evaporation for water and argon as well as the nearest water homolog H 2 S. It is shown that the appearance of this similarity is a consequence of the rotational motion of water molecules, which averages the inter-particle potential in water and leads it to the argon-like form. To describe the fine distinctions in the behavior of the binodals for water, H 2 S and argon the dependence of the proper molecular volume on pressure is taken into account. In accordance with this often used the van der Waals and Carnahan-Starling equations of states are modified. The very surprising behavior of the entropy diameter for water is analyzed. It is shown that the nontrivial details of the temperature dependence for the entropy diameter is directly connected with the peculiarities of the rotational motion of molecules in water. The effect of strong dimerization of water molecules in the fluctuation region near the critical point is studied in details.

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“…( 4) gives unsatisfactory prediction for liquids like water and methanol. Like water, the last is known of its associative properties [17,18].…”

Section: Table Imentioning

confidence: 99%

Surprising properties of water on its binodal as the reflection of the specificity of intermolecular interactions

Kulinskii,

Malomuzh

2009

Preprint

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“…In this work, we report an exact closed-form expression for an association model that allows the formation of monomers, dimers and trimers. This type of association is seen in systems such as acetic acid [10][11][12][13][14][15] propanoic acid [12,15], methanol [16,17], etc. As a demonstration to the importance of using closed-form expressions, we use this monomer-dimer-trimer model to correlate the phase equilibria of acetic acid and compare these results to approximate techniques that one would employ when an exact closed-form expression is not available.…”

Section: Introductionmentioning

confidence: 99%

Association based equation of state for substances forming monomers, dimers and trimers

Baburao¹,

Visco²

2008

Fluid Phase Equilibria

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Studies in hydrogen bonding: Association in methanol using an empirical potential

Brink

Glasser

1981

J Comput Chem

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The empirical potential, EPEN, has been used to establish the structures of isolated hydrogen-bonded clusters in methanol. The most stable configuration of the dimer is found to have a trans near-linear form, whereas the most stable forms of the trimer and tetramer are cyclic. Charge interactions in the tetramer make it the most stable, in terms of energy per hydrogen bond, of these three species. These results are in conformity with various types of experiment. Other species of dimer, trimer, and tetramer, corresponding to local energy minima, have also been identified.A number of experimental studies on the selfassociation of alcohols in the vapor state have been reported.1-6 Most of these studies conclude that the alcohol tetramer1-5 is the most important hydrogen-bonded species, with dimers and especially trimers being considerably less important. Although the dimer is not considered to be an important species in the vapor state, its concentration can be significant in dilute solution of alcohols in nonpolar solvents.7Dyke and co-workers8 have recently reported the molecular beam electric deflection behavior of hydrogen-bonded complexes of methanol and ethanol in the vapor. Dimers are found to be polar, consistent with linear (open) hydrogen-bonded structures, while the results for higher oligomers are consistent with cyclic structures. This is also the conclusion from dielectric studies of alcohols in nonpolar solventsg where the oligomerization sequence with increasing concentration is: monomer-high-dipole-moment open dimer-higher oligomers with cyclic structures and low dipole moments.Two molecular orbital studies of methanol hydrogen bonding have been undertaken. Del BenelO optimized the geometry of the dimer using the STO-3G minimal basis set and found a trans near-linear dimer (TNLD) structure, i.e., -0-H---0-nearly linear, with the methyl groups trans across the -0-Ha . -0-line. Curtissll extended this work by setting up higher methanol oligomers, based on water structures previously optimized by Del Bene and Pople,12 and found that the higher cyclic species are invariably more stable than the corresponding open species. Only the cyclic tetramer was fully optimized, without positional constraints, but no large differences were found compared to the water-based structure. In each case, each methanol molecule was treated by Curtiss as a rigid body having the geometry of the monomer optimized with the STO-3G basis set.It seems useful to extend these calculations on methanol, and eventually to larger alcohol molecules, by finding the unconstrained optimum geometry of each species. However, this would be a large task using ab initio methods, while a semiempirical method (MIND0/3) has recently been shown to be quite inadequate for hydrogenbonding studies.13

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Vapor phase association of methanol. Vapor density evidence for trimer formation

Cited by 18 publications

References 1 publication

Surprising properties of water on its binodal as the reflection of the specificity of intermolecular interactions

Surprising properties of water on its binodal as the reflection of the specificity of intermolecular interactions

Association based equation of state for substances forming monomers, dimers and trimers

Studies in hydrogen bonding: Association in methanol using an empirical potential

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