A study of dimerization in acetonitrile vapor by measurement of thermal conductivity

Renner, T.A.; Blander, M.

doi:10.1021/j100524a012

Cited by 29 publications

(20 citation statements)

References 11 publications

(13 reference statements)

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“…At T ) 41°C and F/F c ≈ 1.62, the equilibrium constant K 1 for the complexation with the monomer varies between 80 and 350 M -1 , depending on the solute; the enthalpy of the complexation is - (15)(16)(17)(18)(19)(20) kJ/mol. The stability of the complexes roughly correlates with the dipole moment of the polar group and the extent of substitution at the R-carbon.…”

Section: Resultsmentioning

confidence: 99%

Solvent Anions in Supercritical Carbon Dioxide: Formation of Complexes with Polar Solutes

and

Sauer

2001

J. Phys. Chem. B

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It is shown that high-mobility multimer (CO 2 ) n •-anions in supercritical (sc)-CO 2 form stable complexes with water, aliphatic alcohols, alkyl halides, and alkyl nitriles. The complexation rate is 10-50% of the diffusion controlled rate or faster. The complexes are formed both with the monomer and with the dimer polar solutes. The equilibrium constants of the monomer complexation range from 10 to 350 M -1 ; the reaction heat is -(15-21) kJ/mol, and the reaction entropy is negative. The stability of the complex increases with the dipole moment of the polar group and decreases with the substitution at the R-carbon. None of these polar solutes directly reacts with quasifree electrons in sc-CO 2 .

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Section: Resultsmentioning

confidence: 99%

Solvent Anions in Supercritical Carbon Dioxide: Formation of Complexes with Polar Solutes

and

Sauer

2001

J. Phys. Chem. B

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“…While neutral dimers, in which the CH 3 CN dipoles are coupled in an antiparallel fashion, readily form in vapor and in liquid [48], the dimer anion,…”

Section: Solvent Anions and Electron Localization In Liquid Acetomentioning

confidence: 99%

“…CH 3 CN is a classical example of a dipole-bound anion, with the electron in a diffuse orbital (> 3 nm) [47]. While neutral dimers, in which the CH 3 CN dipoles are coupled in an antiparallel fashion, readily form in vapor and in liquid [48], the dimer anion, {CH 3 CN} 2 -, has not been observed in the gas phase. In the neutral trimer, one of the monomers couples sideways to the antiparallel pair; this molecule binds the electron in the same way as the monomer; the adiabatic electron affinity of this trimer (14-20 meV) is higher than that of the monomer [47].…”

Section: Solvent Anions and Electron Localization In Liquid Acetonitrilementioning

confidence: 99%

Multimer Radical Ions and Electron/Hole Localization in Polyatomic Molecular Liquids: A Critical Review

Shkrob

Sauer

2004

ChemInform

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Abstract.While ionization of some polyatomic molecular liquids (such as water and aliphatic alcohols) yields so-called "solvated electrons" in which the excess electron density is localized in the interstices between the solvent molecules, most organic and inorganic liquids yield radical anions and cations in which the electron and spin densities reside on the solvent molecule or, more commonly, a group of such molecules. The resulting multimer ions have many unusual properties, such as high rates of diffusive hopping. The "solvated electron" can be regarded as a variant of a multimer radical anion in which the charge, while perturbing the solvent molecules, mainly resides in the space between these molecules. We give several examples of less known modes for electron localization in liquids that yield multimer radical anions (such as C 6 F 6 , benzene, acetonitrile, carbon disulfide and dioxide, etc.) and holes localization in liquids that yield multimer radical cations (such as cycloalkanes). Current understanding of the reaction properties for these high-mobility solvent radical anions and cations is discussed.

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“…The optimized tetramer found" with STO-3G also has this form with 0---0 at 2.50 A and energy -35.59 kcal/mole compared to 2.81 A and -30.56 kcal/mole found here; an experimental AH of -23.73 kcal/mole has been determined for the tetramer formation. 2 While the absolute values of the energies of the various clusters cannot be taken too seriously, the relative values may be instructive. The energy per hydrogen bond of each of the most stable species is lowest for the tetramer (-7.64 kcal/mole), followed by the dimer (-6.76 kcal/mole), and highest for the trimer (-6.18 kcal/mole); the same sequence is found in Curtiss' molecular orbital study."…”

Section: 72mentioning

confidence: 99%

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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A study of dimerization in acetonitrile vapor by measurement of thermal conductivity

Cited by 29 publications

References 11 publications

Solvent Anions in Supercritical Carbon Dioxide: Formation of Complexes with Polar Solutes

Solvent Anions in Supercritical Carbon Dioxide: Formation of Complexes with Polar Solutes

Multimer Radical Ions and Electron/Hole Localization in Polyatomic Molecular Liquids: A Critical Review

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

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