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.

Acyl transfer reactions in the gas phase. The question of tetrahedral intermediates

1981 ◽  
Vol 103 (8) ◽  
pp. 2124-2127 ◽  
Author(s):  
Jhong K. Kim ◽  
Marjorie C. Caserio
Keyword(s):  
Gas Phase ◽  
Acyl Transfer ◽  
Transfer Reactions ◽  
Acyl Transfer Reactions ◽  
Tetrahedral Intermediates

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.

Tetrahedral intermediates formed during acyl transfer. Reactions of acetyl cyanide

1985 ◽  
pp. 1113 ◽  
Author(s):  
Ana M. Lobo ◽  
M. Matilde Marques ◽  
Sundaresan Prabhakar ◽  
Henry S. Rzepa
Keyword(s):  
Acyl Transfer ◽  
Transfer Reactions ◽  
Acyl Transfer Reactions ◽  
Tetrahedral Intermediates

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.

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