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

Guthrie, J. Peter; Pike, David C.; Lee, Yiu-Chung

doi:10.1139/v92-210

Cited by 24 publications

(12 citation statements)

References 17 publications

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“…On the other hand, for esters where OR is attached to an sp2 hybridized carbon the free energy change is almost totally insensitive to electron withdrawal. For R = CF,, CH,, pCH,O-C6H4, C6H5, pN0,-C6H4, AG = +1.65 (20), +1.70 (21), +1.17 (22), +1.26 (22), +1.2 1 (22) (all for reaction in water, where the standard state of water is the pure liquid at unit activity). There does appear to be an effect on changing from an aliphatic to an aromatic acyl substituent, but within each series the effect of drastic change in substituents is very small.…”

Section: Jp ~U T H R I E~mentioning

confidence: 99%

The enols of acetic acid and methyl acetate

Guthrie¹,

Li²

1995

Can. J. Chem.

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Abstract:We have determined the heat of formation of 1,l-dimethoxyethene, AHf(l) = -75.56 ? 0.87 kcal mol-I, by measuring the heat of hydrolysis. The heat of vaporization, 8.47 ? 0.10 kcal mol-I, was estimated from the boiling points at various pressures. The standard entropy of gaseous 1,l-dimethoxyethene, 82.02 ? 2. cal deg-' mol-', was calculated using frequencies obtained by M O calculations at the 6-31G** level. The free energy of transfer, 1.02 2 1, was estimated by additivity with allowance for a distant polar interaction. Thus the free energy of formation in aqueous solution, AGf(aq) = -37.07 ? 1.48 kcal rnol-', could be calculated. ' The free energies of hydrolysis for en01 ethers appear to be insensitive to structure; we used an average value and so calculated the values of the free energies of formation of the enols of acetic acid and methyl acetate, -67.90 2 1.67 and -52.48 2 1.53 kcal mol-I, respectively. These values are in good agreement with other recent evaluations. This method should be applicable to related enols.Key words: enols, thermodynamics, heat of formation, entropy, ketene acetal.

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Section: Jp ~U T H R I E~mentioning

confidence: 99%

The enols of acetic acid and methyl acetate

Guthrie¹,

Li²

1995

Can. J. Chem.

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“…This is in line with the experimentally measured equilibrium constant for the reaction of N , N -dimethylbenzamide 7b and methanol (entry 2), in which the reverse reaction is thermodynamically favored (see Supplementary Information for further discussion). 16 Encouraged by the unique ability of Ni to catalyze the activation of strong aryl –heteroatom bonds, 17 , 18 , 19 particularly those in phenol-, 19 aniline-, 20 , 21 , 22 and phthalimide derivatives, 23 we also calculated the activation energies for acyl C–N bond oxidative addition of each amide substrate using Ni catalysis. The calculated barriers using the commercially available N -heterocyclic carbene (NHC) ligand SIPr (entries 1–8) reveal that the oxidative addition barriers are reasonable in most cases.…”

mentioning

confidence: 99%

Conversion of amides to esters by the nickel-catalysed activation of amide C–N bonds

Hie

Nathel

Shah

et al. 2015

Nature

512

293

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Amides are common functional groups that have been well studied for more than a century.1 They serve as the key building blocks of proteins and are present in an broad range of other natural and synthetic compounds. Amides are known to be poor electrophiles, which is typically attributed to resonance stability of the amide bond.1,2 Whereas Nature can easily cleave amides through the action of enzymes, such as proteases,3 the ability to selectively break the C–N bond of an amide using synthetic chemistry is quite difficult. In this manuscript, we demonstrate that amide C–N bonds can be activated and cleaved using nickel catalysts. We have used this methodology to convert amides to esters, which is a challenging and underdeveloped transformation. The reaction methodology proceeds under exceptionally mild reaction conditions, and avoids the use of a large excess of an alcohol nucleophile. Density functional theory (DFT) calculations provide insight into the thermodynamics and catalytic cycle of this unusual transformation. Our results provide a new strategy to harness amide functional groups as synthons and are expected fuel the further use of amides for the construction of carbon–heteroatom or carbon–carbon bonds using non-precious metal catalysis.

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“…Almeida et al (and Guthrie et al) have reported the molar standard enthalpy of formation for M4MB in the crystalline phase as −(523.8 ± 2.3) kJ·mol –1 (and as −(520.91 ± 1.63) kJ·mol –1 ). As one can observe, our result, −(527.7 ± 2.7) kJ·mol –1 , agrees with Almeida et al’s value, and the difference is within the experimental uncertainties.…”

Section: Resultsmentioning

confidence: 99%

Thermochemical Study of Methyl n-Methoxybenzoates: An Experimental and Computational Approach

et al. 2019

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In this work, we determine, both experimentally and computationally, structural and thermochemical properties of the methyl 2- and 4-methoxybenzoates. Combustion and vaporization enthalpies of these compounds were obtained experimentally through combustion calorimetry and thermogravimetry. From these properties, their standard molar enthalpies of formation in the gas phase, at T = 298.15 K, were also determined. In addition, we computed gas-phase enthalpies of formation of methyl 2-, 3-, and 4-methoxybenzoates using the composite method Gaussian G4, atomization reactions, and a weighted Boltzmann average. This average was performed over the stable conformers of each compound, and the respective Gibbs energies were used to compute the weights for the Boltzmann average. The analyses of the electronic density of the molecules and of noncovalent interactions were performed as well. We found a good agreement between our experimental and computational enthalpies of formation of methyl 2- and 4-methoxybenzoates. Finally, we discuss the enthalpic effects, as a function of the relative position of the methoxy and methyl groups, upon the benzoate base structure.

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

Cited by 24 publications

References 17 publications

The enols of acetic acid and methyl acetate

The enols of acetic acid and methyl acetate

Conversion of amides to esters by the nickel-catalysed activation of amide C–N bonds

Thermochemical Study of Methyl n-Methoxybenzoates: An Experimental and Computational Approach

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