Equilibrium constants and heats of formation of methyl esters and N,N-dimethyl amides of substituted benzoic acids

1992 ◽  
Vol 70 (6) ◽  
pp. 1671-1683 ◽  
Author(s):  
J. Peter Guthrie ◽  
David C. Pike ◽  
Yiu-Chung Lee
Keyword(s):  
Methyl Esters ◽  
Equilibrium Constants ◽  
Heats Of Formation ◽  
Free Energies ◽  
Ester Formation ◽  
Free Energy Of Transfer ◽  
Partition Constants ◽  
Substituted Benzoic Acids ◽  
Energy Of Transfer ◽  
Benzoyl Chlorides

Heats of methanolysis and dimethylaminolysis of substituted benzoyl chlorides (4-X-C6H4-COCl, X = H, CH3, OCH3, Cl, NO2) have been measured, as have the heats of hydrolysis of the esters, permitting the calculation of the heats of formation of the benzoyl chlorides (4-X-C6H4-COCl, X, DHf: CH3O, −80.29 ± 0.70; CH3, −48.10 ± 1.46; NO2, −47.70 ± 0.87), methyl benzoate esters (4-X-C6H4-COOCH3, X, DHf: CH3O, −124.50 ± 0.39; CH3, −93.99 ± 0.58; Cl, −92.09 ± 0.53; NO2, −92.55 ± 0.31), and N,N-dimethylbenzamides (4-X-C6H4-CON(CH3)2, X, DHf: CH3O, −75.87 ± 1.42; CH3, −46.62 ± 1.99; H, −40.96 ± 1.41; Cl, −49.33 ± 1.09; NO2, −48.05 ± 1.53). Free energies of transfer from methanol to water and from gas to water were determined for the esters and amides. Free energies of formation in aqueous solution were calculated for the acids, esters and amides, making use of thermodynamic estimation procedures where necessary. Equilibrium constants were measured for ester formation in water (X, K (M−1): CH3O, 0.14; CH3, 0.14; H, 0.12; Cl, 0.15; NO2, 0.13) and N,N-dimethylaminolysis in methanol (X, K (M−1): CH3O, 8.16; CH3, 17.5; H, 26.5; Cl, 22.6; NO2, 41.0). Partition constants for esters and amides were measured for methanol/dodecane and dodecane/water, permitting calculation of the free energy of transfer from methanol to water (4-X-C6H4-COOCH3, X, DGmw: CH3O, 3.12; CH3, 3.17; H, 3.01; Cl, 3.43; NO2, 2.89; 4-X-C6H4-CON(CH3)2, X, DGmw: CH3O, 0.96; CH3, 1.48; H, 0.92; Cl, 1.77; NO2, 0.99). These data permit calculation of the equilibrium constants for dimethylaminolysis of substituted methyl benzoates in water, and for amide formation in water (4-X-C6H4-CON(CH3)2, X, K(M−1, reactants and products as neutral molecules): CH3O, 767; CH3, 752; H, 2050; Cl, 1020; NO2, 2350). In the course of our calorimetric measurements we derived an improved value for the heat of solution of HCl in methanol.

Thermodynamics of transfer of Ph4C; scaled-particle theory and the Ph4As+/Ph4B− assumption for single ions

1979 ◽  
Vol 57 (15) ◽  
pp. 2004-2009 ◽  
Author(s):  
Michael H. Abraham ◽  
Asadollah Nasehzadeh
Keyword(s):  
Free Energy ◽  
Total Free Energy ◽  
Scaled Particle Theory ◽  
Free Energies ◽  
Particle Theory ◽  
Free Energy Of Transfer ◽  
Enthalpy And Entropy ◽  
Interaction Term ◽  
Energy Of Transfer ◽  
Entropy Of Transfer

Free energies of transfer of Ph4C from acetonitrile to 20 other solvents have been calculated from literature data. The contribution of the cavity term to the total free energy has been obtained from scaled-particle theory and Sinanoglu–Reisse–Moura Ramos theory. It is shown that there is little connection between the cavity term and the total free energy of transfer, and that there must be, in general, a large interaction term. If the latter is important for transfer of Ph4C, we argue that it must also be important for transfer of the ions Ph4As+ and Ph4B−. Previous suggestions that the interaction term is zero for transfer of these two ions are thus seen to be unreasonable. We also show, for six solvents, that the interaction term for Ph4C is very large in terms of enthalpy and entropy, and that scaled-particle theory seems not to apply to transfers of Ph4C between pure organic solvents.The free energy, enthalpy, and entropy of transfer of Ph4As+ = Ph4B− have been calculated by dividing the total transfer values into neutral and electrostatic contributions; reasonable agreement is obtained between calculated and observed values.

Comparison of the free energy of transfer of electrolytes, measured with cells without transference, with the sum of the free energies of the corresponding cations and anions with the Owen-cell on standard conditions

1983 ◽  
Vol 36 (10) ◽  
pp. 1997 ◽  
Author(s):  
K Schwabe ◽  
W Hoffmann ◽  
C Queck
Keyword(s):  
Free Energy ◽  
Free Energies ◽  
Liquid Junction Potential ◽  
Liquid Junction ◽  
Ph Values ◽  
Liquid Junction Potentials ◽  
Free Energy Of Transfer ◽  
Energy Of Transfer ◽  
Very High ◽  
Junction Potential

The comparison of S2ΔS1G°tr(E1) with the sum of the values for the corresponding cation and anion S2ΔS1G°tr(Ct+)~S2ΔS1G°tr(X-) (measured) with Owen cells, gained by double extrapolation and by the assumption that the liquid junction potential at 1→0 may be neglected) gives values which differ by not more than ±5%. Most of the investigated acids allow the conclusion that the pH values, measured in cells with transference, and having the same electrodes, give good information on the acidity of the organic solvent and its water mixtures, referred to the standard state in water. That means that the pH, changed to the same H+ concentration in the solvent compared with that in water, is essentially an effect of the free energy of transfer of the hydrogen ion and not of very high liquid junction potentials.

Cyclization of glycol monoesters to give hemiorthoesters: a test of the thermochemical method for determining free energies of tetrahedral intermediates

1977 ◽  
Vol 55 (20) ◽  
pp. 3562-3574 ◽  
Author(s):  
J. Peter Guthrie
Keyword(s):  
Ethylene Glycol ◽  
Equilibrium Constants ◽  
Heat Of Formation ◽  
Acyl Transfer ◽  
Heats Of Formation ◽  
Free Energies ◽  
Tert Butyl ◽  
Thermochemical Method ◽  
Acyl Transfer Reactions ◽  
Tetrahedral Intermediates

From calorimetric heat of formation data, free energies of cyclization (to the hemior-thoester) for the following glycol monoesters have been calculated: ethylene glycol monoformate, +7.54; ethylene glycol monoacetate, +10.72; pinacol monoformate, +3.21; ethylene glycol monotrifluoroacetate, +2.83; pinacol monotrifluoroacetate, −3.38. The latter two results are shown to be in satisfactory agreement with experimental results. This investigation represents a further test of the thermochemical method for calculating free energies of tetrahedral intermediates in acyl transfer reactions which was reported earlier.In the course of this work, various thermochemical quantities were determined. Heats of reaction for the process:[Formula: see text]have been measured for three compounds: 1, R = H, R′ = CH3, R″ = H; x = 0.92, ΔHobs = −7.13 ± 0.60 kcal/mol; 2, R = H, R′ = CH3, R" = CH3; x = 0.98, ΔHobs = −10.11 ± 0.40 kca1/mol; 9, R = CH3, R′ = C2H5, R″ = H; x = 0.98, ΔHobs = −4.76 ± 0.19 kcal/mol. From these may be obtained heats of formation of the liquids: 1, −126.01 ± 0.94; 2, −137.25 ± 0.87; 9, −173.87 ± 2.09 kcal/mol. For some related esters, heats of hydrolysis were measured, leading to the following heats of formation of the liquids: tert-butyl formate, −117.85 ± 0.80; tert-butyl trifluoroacetate, −271.28 ± 1.14; pinacol monoformate, −175.02 ± 2.12 kcal/mol. Heats of hydrolysis were measured for methoxyethyl formate and acetate, but in the absence of a reliable value for the heat of formation of methoxyethanol, do not lead to calorimetric heats of formation. Equilibrium constants for formation of the monoesters of ethylene glycol with formic, acetic, and trifluoroacetic acids were measured (nmr analysis of equilibrated solutions) and lead to free energies of hydrolysis of −2.34, −1.65, and −2.75 kcal/mol respectively.

Concerning the distant polar interaction in free energies of transfer. An explanation and an estimation procedure

1991 ◽  
Vol 69 (12) ◽  
pp. 1893-1903 ◽  
Author(s):  
J. Peter Guthrie
Keyword(s):  
Free Energy ◽  
Hydrogen Bonding ◽  
Estimation Procedure ◽  
Free Energies ◽  
Polar Interaction ◽  
Free Energies Of Transfer ◽  
Polar Groups ◽  
Polyfunctional Compounds ◽  
Free Energy Of Transfer ◽  
Energy Of Transfer

For polyfunctional compounds, free energies of transfer from gas to aqueous solution require corrections for the interactions of polar groups (Distant Polar Interactions). These corrections can be made with very few adjustable parameters by using a model of the solvation process assuming hydrogen bonding is the major source of the effect on free energy of transfer for polar groups, and that hydrogen bonding is perturbed by polar effects, measured by Taft σ*. Parameters evaluated for polyfluoro, polychloro, and polybromo compounds successfully predicted the free energies of transfer for mixed polyhalogen compounds. Preliminary parameters have been evaluated for ethers, amines, phenyl groups, nitriles, and esters. Key words: free energy of transfer, distant polar interaction, hydrogen bonding, solvation.

The spectrophotometric solvent sorting method for the determination of free energies of transfer of individual ions—a critical appraisal

1983 ◽  
Vol 36 (9) ◽  
pp. 1739 ◽  
Author(s):  
CF Wells
Keyword(s):  
First Principles ◽  
Structural Changes ◽  
Critical Appraisal ◽  
Solvent Mixtures ◽  
Free Energies ◽  
Dominant Effect ◽  
Free Energy Of Transfer ◽  
Solvent Molecules ◽  
Energy Of Transfer

The spectrophotometric method for determining values for the free energy of transfer of the proton from water into water + co-solvent mixtures at mole fractions of co-solvent up to x2 ≈ 0.3 is examined critically from first principles. It is found that some corrections become significant at the higher x2 in this range and these are applied to all the co-solvents used. The new values for ΔGt�(H+) are then used to calculate new values for ΔGt� (X-) from ΔGt�(HX) and new values for ΔGt�(M+) and (M2+)from ΔGt�(MX) and ΔGT�(MX2). New electrochemical, solubility and pK data are incorporated into these calculations, resulting in ΔGt� values for some additional ions for several co-solvents. The ΔGt� values for all co-solvents are compared and contrasted, and it is concluded that structural changes in the solvent have a dominant effect in determining these values. The evidence for molecular rearrangements involving solvent molecules in the neighbourhood of the ions resulting from the transfer is examined.

Effect of the acyl substituent on the equilibrium constant for hydration of esters

1980 ◽  
Vol 58 (13) ◽  
pp. 1281-1294 ◽  
Author(s):  
J. Peter Guthrie ◽  
Patricia A. Cullimore
Keyword(s):  
Aqueous Solution ◽  
Equilibrium Constant ◽  
Rate Constant ◽  
Rate Constants ◽  
Acid Catalysis ◽  
Methyl Esters ◽  
Equilibrium Constants ◽  
Free Energies ◽  
General Acid ◽  
Aldehydes And Ketones

Heats of hydrolysis have been measured for the trimethyl orthoesters of isobutyric, propionic, benzoic, methoxyacetic, chloroacetic, and cyanoacetic acids using aqueous acid with an organic cosolvent where necessary, and of the corresponding esters in alkaline solution. Solubilities or free energies of transfer from gas to aqueous solution have been measured, permitting calculation of the free energies of formation of the aqueous orthoesters, and by methods which we have published previously, calculation of the free energies of formation of the covalent hydrates of the esters, and the free energy changes for hydration of these esters.Using estimated pKa values equilibrium constants were calculated for the addition of hydroxide to the esters. The data are in good agreement with the appropriate Marcus equation relating rate and equilibrium constants with a value for b of 8.99 ± 0.17. This line was used to estimate the equilibrium constant for addition of hydroxide, and thence of water, to some additional esters where only the rate constant was available. Rate constants for hydrolysis of methyl esters in aqueous solution at 25 °C were calculated from literature data, correcting for the effect of other conditions as necessary. From the equilibrium constants for addition of water we could estimate the rate constants for uncatalyzed hydrolysis; for the cases where this rate constant has been measured, the agreement was satisfactory. For acid catalyzed hydrolysis the data permit a test of the two alternative mechanisms considered previously, namely specific acid catalysis and general acid catalysis with hydronium ion acting as a general acid. For esters the mechanism is clearly specific acid catalysis, but for aldehydes and ketones it appears very likely that the mechanism is general acid catalysis.

A Theoretical Study of Substituted Stepwise Fluorinated Cyclopropanone Keto-Enol System

2003 ◽  
Vol 58 (12) ◽  
pp. 749-755
Author(s):  
Abdullah El-Alali ◽  
Ali A. Marashdeh ◽  
Salim M. Khalil
Keyword(s):  
Theoretical Study ◽  
Dipole Moments ◽  
Heats Of Formation ◽  
Geometrical Parameters ◽  
Free Energies ◽  
Isodesmic Reactions ◽  
Orbital Energies ◽  
Substantial Concentration ◽  
Homo Lumo ◽  
Complete Optimization

MINDO-Forces calculations have been performed with complete optimization of the geometries on stepwise fluorinated cyclopropanones and their enols. Increase in the number of fluorine atoms causes destabilization of cyclopropanone. Perfluorinated enol was found to be present in substantial concentration, as was mentioned in previous work. This is supported by calculations of Gibbs free energies and isodesmic reactions. Geometrical parameters, heats of formation, electron densities, dipole moments and orbital energies (HOMO-LUMO) are reported.

MINDO-Forces Study on Substituted Nitromethane ⇋ aci-Nitromethane Tautomerism

2005 ◽  
Vol 60 (1-2) ◽  
pp. 47-53
Author(s):  
Bareehan M. Salim ◽  
Salim M. Khalil
Keyword(s):  
Theoretical Calculations ◽  
Geometry Optimization ◽  
Heats Of Formation ◽  
Geometrical Parameters ◽  
Free Energies ◽  
Electron Densities ◽  
Isodesmic Reactions ◽  
Complete Geometry Optimization

MINDO-Forces calculations with complete geometry optimization have been performed on nitromethane, aci-nitromethane and X-substituted nitromethane and aci-nitromethane (X = F, OH, NH2, CH3, CN, CF3, NO2, CHO). It is found that nitromethane is more stable than aci-nitromethane by 9.337 kcal/mol. This agrees with theoretical calculations. Thermodynamically, substituted aci-nitro tautomers are more stable than the corresponding nitromethane, except in case of the substituent F. Geometrical parameters, heats of formation, electron densities, Gibbs free energies and isodesmic reactions are reported.

Solvation in hydroorganic media—I. Gibbs free energy of transfer for RbCl from cationic glass electrode measurements

1976 ◽  
Vol 21 (6) ◽  
pp. 425-430 ◽  
Author(s):  
R. Smits ◽  
D.L. Massart ◽  
J. Juillard ◽  
J.-P. Morel
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Glass Electrode ◽  
Free Energy Of Transfer ◽  
Energy Of Transfer

Microemulsion as Model to Predict Free Energy of Transfer of Electrolyte in Solvent Extraction

2021 ◽  
pp. 1-36
Author(s):  
Simon Gourdin-Bertin ◽  
Jean-François Dufrêche ◽  
Magali Duvail ◽  
Thomas Zemb
Keyword(s):  
Free Energy ◽  
Solvent Extraction ◽  
Free Energy Of Transfer ◽  
Energy Of Transfer
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