Enthalpies of interaction of polar and nonpolar molecules with aromatic solvents

1982 ◽  
Vol 60 (15) ◽  
pp. 1953-1958 ◽  
Author(s):  
Richard Fuchs ◽  
L. Alan Peacock ◽  
W. Kirk Stephenson
Keyword(s):  
Hydroxyl Group ◽  
Enthalpies Of Solution ◽  
Butyl Ether ◽  
Aromatic Solvent ◽  
Aromatic Solvents ◽  
Induced Dipole ◽  
Or Groups ◽  
Polar Solutes ◽  
Base Method ◽  
Heats Of Vaporization

Enthalpies of solution of representative ketones, phenols, alcohols, and ethers have been determined in α,α,α-trifluorotoluene, benzene, toluene, and mesitylene, and combined with heats of vaporization to give enthalpies of transfer from vapor to the aromatic solvents [ΔH(v→S)]. Comparison of these values with ΔH(v→S) of nonpolar model compounds provides an estimate of the special interactions (dipole – induced dipole or charge transfer, and hydrogen bonding) of the polar solutes with each aromatic solvent. Unless the model compound is perfectly matched, an alternative procedure, the pure base method, is superior for evaluating hydrogen bonding.The special interactions of ketones and ethers with aromatic solvents increase with decreasing π electron density of the solvent. By contrast, m-cresol shows the strongest special interaction with the most electron-rich solvent (mesitylene > toluene > benzene > trifluorotoluene). These results demonstrate that —OH and —OR groups undergo quite different interactions, and that a distinctive interaction occurs between the hydroxyl group and the aromatic ring.Calorimetric heats of vaporization have been measured for the solutes n-butyl ether (10.68 ± 0.02 kcal/mol), 2,2,4,4-tetramethylpentane (9.20 ± 0.03), n-pentane (6.36 ± 0.02), 1-butanol (12.46 ± 0.00), and 2-methyl-2-butanol (11.94 + 0.02).

Hydrogen bonding and other polar interactions of 1-, 2-, and 4-octyne with organic solvents

1983 ◽  
Vol 61 (9) ◽  
pp. 2044-2047 ◽  
Author(s):  
John H. Hallman ◽  
W. Kirk Stephenson ◽  
Richard Fuchs
Keyword(s):  
Hydrogen Bond ◽  
Bond Formation ◽  
Butyl Ether ◽  
Hexamethylphosphoric Triamide ◽  
Hydrogen Bond Formation ◽  
Enthalpies Of Transfer ◽  
Induced Dipole ◽  
Base Method ◽  
Polar Interactions ◽  
Heats Of Vaporization

The heats of vaporization of 1-octyne (10.11 ± 0.02 kcal/mol), 2-octyne (10.63 ± 0.03 kcal/mol), and 4-octyne (10.21 ± 0.02 kcal/mol) have been determined. Heats of solution of the liquid octynes and n-octane have been measured in heptane, cyclohexane, 1,2-dichloroethane, n-butyl ether, ethanol, triethylamine, dimethyl sulfoxide, butyrolactone, dimethylformamide, and hexamethylphosphoric triamide. Enthalpies of transfer from vapor to each solvent have been calculated. Enthalpies of hydrogen bond formation, calculated by the pure base method, become more exothermic in the above solvent order. Correlations with the Taft–Kamlet solvent parameters π* and β indicate that other polar interactions (presumably dipole – induced dipole) are appreciably larger for 1-octyne than for 2- and 4-octyne.

SOLVENT EFFECTS ON THE PROTON RESONANCE SPECTRA OF THE DICHLORO- AND DIBROMO-ETHYLENES: REACTION FIELD EFFECTS IN ALIPHATIC SOLVENTS AND SPECIFIC INTERACTIONS IN AROMATIC SOLVENTS

1963 ◽  
Vol 41 (12) ◽  
pp. 3034-3041 ◽  
Author(s):  
F. Hruska ◽  
E. Bock ◽  
T. Schaefer
Keyword(s):  
Field Effect ◽  
Dielectric Constants ◽  
Specific Interactions ◽  
Proton Resonance ◽  
Water Solutions ◽  
Reaction Field ◽  
Aromatic Solvents ◽  
Triple Bonds ◽  
Induced Dipole ◽  
Cis And Trans

The proton resonance shifts relative to internal cyclohexane and tetramethylsilane of cis and trans dichloro- and dibromo-ethylenes were measured in dioxane–water solutions, aliphatic solvents, and aromatic solvents. The dielectric constants of the dioxane–water solutions could be smoothly varied between 2 and 10 and, by taking Δ = cis–trans shifts as containing only the dipolar reaction field effect, the data for these solutions were treated as a test of the Buckingham reaction field equation. Linear plots were obtained and reasonable values of the coefficients of the E term confirmed the usefulness of this equation. An equation based on a nonspherical cavity was also used. It was also shown that quadrupolar reaction fields affected the proton shifts. Sizeable deviations from the dioxane–water standards were found for halogenated aliphatic solvents and those containing double or triple bonds. These deviations are interpreted in terms of the shape of the solute molecules and dispersion and anisotropic interactions. The much larger deviations found for aromatic solvents are harder to rationalize but specific interactions were found for both cis and trans forms, indicating an inadequacy in a simple dipole-induced dipole model.

Applications of the intermolecular nuclear Overhauser effect. II. The operation of solute-site factors in the interaction of polar solutes with the solvent benzene

1983 ◽  
Vol 36 (11) ◽  
pp. 2227 ◽  
Author(s):  
GR Smith ◽  
B Ternai
Keyword(s):  
Nuclear Overhauser Effect ◽  
Proton Relaxation ◽  
Relaxation Rates ◽  
Site Factors ◽  
Aromatic Solvent ◽  
Proton Proton ◽  
Solvent Interactions ◽  
Overhauser Effect ◽  
Polar Solutes ◽  
Nuclear Overhauser

By considering the technique involving the measurement of aromatic solvent-induced shifts, and the models which have been proposed from the results of such measurements, it is suggested that the use of the solvent-induced solute proton intermolecular relaxation rate [(1/T1)solvinter] is a better method to study local solvation of solute molecules. Proton relaxation rates obtained for simple solutes in the solvent benzene are analysed in terms of an interaction parameter I, which treats (1/T1)solvinter] in terms of a proton-proton pair distribution function. The resultant dependence between I and a calculated measure of the local polarity of the observed solute is discussed in terms of previously proposed models of solute-solvent interactions.

Enthalpies of hydrogen bond formation of 1-octanol with aprotic organic solvents. A comparison of the solvation enthalpy, pure base, and non-hydrogen-bonding baseline methods

1985 ◽  
Vol 63 (2) ◽  
pp. 342-348 ◽  
Author(s):  
W. Kirk Stephenson ◽  
Richard Fuchs
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Bond Formation ◽  
Enthalpies Of Solution ◽  
Dispersion Interactions ◽  
Butyl Ether ◽  
Hydrogen Bond Formation ◽  
Solvation Enthalpy ◽  
Benzene Toluene ◽  
Good Agreement

Enthalpies of solution (ΔHs) of 1-octanol and five model compounds (di-n-butyl ether, n-heptyl methyl ether, 1-fluoro-octane, 1-chlorooctane, and n-octane) have been determined in 13 solvents (heptane, cyclohexane, CCl4, 1,1,1-trichloro-ethane, 1,2-dichloroethane, triethylamine, butyl ether, ethyl acetate, DMF, DMSO, benzene, toluene, mesitylene), and combined with heats of vaporization to give enthalpies of transfer from vapor to solvent (ΔH(v → S)). These values have been used to calculate the enthalpy of hydrogen bond formation (ΔHh) of 1-octanol with each solvent, using the pure base (PB), solvation enthalpy (SE), and non-hydrogen-bonding baseline (NHBB) methods. Evidence is presented suggesting that (a) the SE method is susceptible to mismatches of the 1-octanol vs. model polar and dispersion interactions, (b) the PB method is sensitive to polar interaction mismatches, whereas (c) the NHBB method compensates for both polar and dispersion interactions mismatches. The (apparent) ΔHh values determined by the SE and PB methods may be as much as several kcal/mol (nearly 50%) too large, because of the inclusion of other polar and dispersion interactions. The NHBB method is therefore preferred for determining enthalpies of H-bond formation from calorimetric data. However, apparent ΔHh values from the SE and PB methods can be incorporated into total solvatochromic equations using Taft–Kamiet π*, β, and ξ parameters, to provide enthalpies of H-bond formation in good agreement with ΔHh (NHBB).

Limiting activity coefficients in dilute solutions of nonelectrolytes. I.Determination for polar–nonpolar binary mixtures by a novel apparatus, and a solubility-parameter treatment of results

1982 ◽  
Vol 60 (21) ◽  
pp. 2697-2706 ◽  
Author(s):  
Etela Milanová ◽  
Genille C. B. Cave
Keyword(s):  
Binary Mixtures ◽  
Activity Coefficients ◽  
Solubility Parameter ◽  
Butyl Acetate ◽  
Dipole Interaction ◽  
Polar Compounds ◽  
Polar Component ◽  
Nonpolar Solvents ◽  
Induced Dipole ◽  
Polar Solutes

The activity coefficients of several solutes in dilute binary solutions of nonelectrolytes were determined at 20 °C from vapour–liquid equilibria in a novel static equilibration apparatus, by gas-chromatographic analysis of the equilibrium vapor phase. The solutes were nitromethane, nitroethane, 1-nitropropane, 2-nitropropane, acetonitrile, propionitrile, ethyl acetate, and n-butyl acetate in n-heptane and in benzene as solvents, and also carbon tetrachloride as solute in each of the above-listed polar compounds as the solvent.The modifications by Weimer and Prausnitz and by Blanks and Prausnitz to the Scatchard–Hildebrand equation in order to accommodate binary mixtures containing a polar component were tested by using the values found in the present work for the limiting activity coefficients of these solutes. In addition, it was found that the ratio of the dipole – induced dipole interaction parameter for polar solutes in the two nonpolar solvents was nearly constant.Three methods for evaluating the dispersion contribution to the solubility parameter of a polar compound were considered.

Enthalpies of solution, limiting solubilities, and partial molar heat capacities of n-alcohols in water and in trehalose crowded media

2014 ◽  
Vol 86 (2) ◽  
pp. 223-231 ◽  
Author(s):  
Guangyue Bai ◽  
Sandra C.C. Nunes ◽  
Marisa A.A. Rocha ◽  
Luís M.N.B.F. Santos ◽  
M. Ermelinda S. Eusébio ◽  
...  
Keyword(s):  
Heat Capacity ◽  
Molar Heat Capacity ◽  
Enthalpy Of Solution ◽  
Biological Fluids ◽  
Aqueous Media ◽  
Aqueous Solubility ◽  
Enthalpies Of Solution ◽  
Partial Molar Heat Capacity ◽  
Polar Solutes ◽  
Hydrophobic Solvation

Abstract The enthalpies of solution of alcohols were determined by calorimetry in HEPES and (HEPES + trehalose) at 298.15 K. The used methodology and experiment’s design allowed us to extract from a single titration experiment the enthalpy of solution (ΔsolHm), the limiting solubility of the alcohol in each aqueous media, and an estimation of the enthalpy of solution of water in the alcohol phase. From these values the changes in Gibbs energy (ΔsolGm) and in entropy (ΔsolSm) of solution were derived. A decrease in solubility for 1-butanol and 1-pentanol in the crowded media (HEPES + trehalose) was observed which is driven by a significant decrease in the favorable enthalpy of solution. The partial molar heat capacity, in each media was determined in our heat capacity drop calorimeter, also at 298.15 K. A significant decrease of the partial molar heat capacity was observed for both alcohols in (HEPES + trehalose), which together with the obtained decrease in favorable ΔsolHm, is consistent with a decrease in hydrophobic solvation, as a result of a decrease in free solvent availability induced by the trehalose. Finally, we tentatively predict that in the aqueous media of the crowded solutions that characterize cells and biological fluids, solutes with low aqueous solubility will be more soluble, whereas the solubility of highly polar solutes will be reduced.

A NUCLEAR MAGNETIC RESONANCE INVESTIGATION OF MOLECULAR COMPLEXES OF POLAR MOLECULES IN AROMATIC SOLVENTS

1962 ◽  
Vol 40 (7) ◽  
pp. 1285-1290 ◽  
Author(s):  
J. V. Hatton ◽  
W. G. Schneider
Keyword(s):  
Molecular Complex ◽  
Molecular Complexes ◽  
Large Temperature ◽  
Proton Resonance ◽  
Aromatic Solvents ◽  
Temperature Coefficients ◽  
Molecular Complex Formation ◽  
Nuclear Magnetic Resonance Investigation ◽  
Polar Solutes ◽  
Magnetic Resonance Investigation

In order to confirm the existence of specific molecular complexes in solutions of polar solutes in aromatic solvents previously proposed, the temperature variation of the proton resonance shifts of the solutes acetonitrile, p-benzoquinone, and N,N-dimethylformamide in 5 mole% concentration in toluene were measured. The large temperature coefficients of the solute shifts observed strongly support molecular complex formation. For the same solutes dissolved in methylcyclohexane the temperature coefficients were negligibly small. The temperature at which onset of free rotation of the N-dimethyl group of N,N-dimethylformamide occurs is solvent and concentration dependent. These observations are consistent with the proposed geometry of the molecular complex in the aromatic solvents.

The chemical shifts of the methoxyl in anisole derivatives

1973 ◽  
Vol 26 (10) ◽  
pp. 2303 ◽  
Author(s):  
S Ng
Keyword(s):  
Chemical Shifts ◽  
Spin Coupling ◽  
Proton Resonance ◽  
Aromatic Solvent ◽  
Upfield Shift ◽  
Aromatic Solvents ◽  
Meta Position ◽  
Doublet Structure ◽  
Alkyl Substitution ◽  
Spin Spin Coupling

The n.m.r. spectra of anisole and 20 methyl-, t-butyl-, adamant-1-yl-, and chloro-substituted anisoles were obtained in dilute solutions in CCl4, CHCl3, and C6H6. In the non-aromatic solvents the methoxyl proton resonance shifts upfield with di-o-alkyl substitution, relative to anisole or o-alkyl substitution. However, this upfield shift is not observed in the case of di-o-chloro substitution. In benzene the methoxyl resonance exhibits the aromatic-solvent induced shift, and this shift is larger with ortho than with di-ortho substitution. Relative to anisole, alkyl substitution at the para or meta position shifts the methoxyl resonance slightly upfieid in the non-aromatic solvents, but slightly downfield in benzene. However, chloro substitution at the ortho or the para position shifts this resonance upfield in benzene. In the mono-o-substituted derivatives, the methoxyl resonance shows a doublet structure, consistent with spin-spin coupling with the o-proton (J c. 0.20 Hz).

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