Substituent Effects on the Energetics and Aromaticity of Aminomethylbenzoic Acids

Lima, Carlos F. R. A. C.; Gomes, Lígia R.; Santos, Luı́s M. N. B. F.

doi:10.1021/jp073077j

Cited by 20 publications

(6 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…According to NICS(0) and NICS(±1) ZZ values (Table ), cis -2-hydroxypyridine is more aromatic than cis -4-hydroxypyrimidine, and 2-pyridinone is more aromatic than 4(3 H )-pyrimidinone. This is a consequence of more extensive conjugation of the hydroxyl and the carbonyl functional groups with the two nitrogen atoms of the pyrimidine ring instead of only one nitrogen of pyridine, which lowers the aromaticity of the ring according to the NICS criterion of aromaticity, as described in previous studies. − …”

Section: Resultsmentioning

confidence: 83%

From 2-Hydroxypyridine to 4(3H)-Pyrimidinone: Computational Study on the Control of the Tautomeric Equilibrium

et al. 2013

View full text Add to dashboard Cite

In this work is investigated why the entrance of a nitrogen atom in the ring of cis-2-hydroxypyridine and 2-pyridinone, resulting in cis-4-hydroxypyrimidine and 4(3H)-pyrimidinone, respectively, shifts the tautomeric equilibrium from the hydroxyl form, in the pyridine derivative, to the ketonic form, in the pyrimidine derivative. The conclusions obtained for these model systems allow us to understand how to control the gaseous-phase keto-enol tautomeric equilibrium in nitrogen heterocyclic rings and justify the tautomeric preference in pyrimidine nucleobases. The experimental and computational energetics of tautomeric equilibrium were interpreted in terms of the aromaticity, intramolecular hydrogen bonds, and electronic delocalization, evaluated using nucleus independent chemical shifts, quantum theory of atoms in molecules, natural bond orbital analysis, and the thermodynamic changes of appropriate reactions.

show abstract

Section: Resultsmentioning

confidence: 83%

From 2-Hydroxypyridine to 4(3H)-Pyrimidinone: Computational Study on the Control of the Tautomeric Equilibrium

et al. 2013

View full text Add to dashboard Cite

show abstract

“…Our research group has been investigating the volatility of differently substituted benzoic acids − through vapor pressure measurements at different temperatures. For some of these compounds enthalpies of combustion were also measured, ,, enabling the determination of the enthalpy of formation in the crystalline and gaseous phases. This work continues the studies of volatility and enthalpies of formation of substituted benzoic acids.…”

Section: Introductionmentioning

confidence: 99%

Vapor Pressures and Enthalpies of Combustion of the Dihydroxybenzoic Acid Isomers

2009

View full text Add to dashboard Cite

The Knudsen mass-loss effusion technique was used to measure the vapor pressures at different temperatures of the following dihydroxybenzoic acids : 2,3-dihydroxybenzoic acid, between (345.22 and 363.18) K; 2,4dihydroxybenzoic acid, between (376.22 and 392.11) K; 2,5-dihydroxybenzoic acid, between (372.14 and 388.92) K; 2,6-dihydroxybenzoic acid, between (347.14 and 365.17) K; 3,4-dihydroxybenzoic acid, between (387.12 and 403.26) K; and 3,5-dihydroxybenzoic acid, between (345.22 and 363.18) K. From the temperature dependences of the vapor pressure of the crystalline compounds, the standard (p 0 ) 10 5 Pa) molar enthalpies and Gibbs energies of sublimation, at T ) 298.15 K, were derived. For each of the six isomers the standard (p 0 ) 0.1 MPa) molar enthalpy of formation in the crystalline phase was derived from the experimental standard molar energy of combustion, in oxygen, measured by static-bomb combustion calorimetry at T ) 298.15 K. The combination of the standard molar enthalpy of formation in the crystalline phase with the standard enthalpy of sublimation yields the standard molar enthalpy of formation in the gaseous phase of the studied compounds.

show abstract

“…The assessment of aromaticity of the pyridine ring of the three diphenylpyridine isomers was performed using the NICS method. This method has been widely applied to evaluate the aromaticity of aromatic organic compounds. − The NICS probes (Bq) were placed at the geometric center of the pyridine ring, perpendicular to the average of the pyridine plane, from −2 to +2 Å, in increments of 0.2 Å. The NICS values were calculated for all ghost atoms using the standard GIAO procedure at the B3LYP/6-311++G(d,p) level of theory.…”

Section: Computational Sectionmentioning

confidence: 99%

Energetic and Structural Study of Diphenylpyridine Isomers

et al. 2009

Self Cite

View full text Add to dashboard Cite

The energetic and structural study of three diphenylpyridine isomers is presented in detail. The three isomers, 2,6-, 2,5-, and 3,5-diphenylpyridines, were synthesized via Suzuki-Miyaura methodology based on palladium catalysis, and the crystal structures of the isomers were obtained by X-ray diffraction. The relative energetic stabilities in the condensed and gaseous phases as well as volatilities and structures of the three studied isomers were evaluated, regarding the position of the phenyl groups relative to the nitrogen atom of the pyridine ring. The temperature, standard molar enthalpies, and entropies of fusion were measured and derived by differential scanning calorimetry. The vapor pressures of the considered isomers were determined by a static apparatus based on a MKS capacitance diaphragm manometer. The standard molar enthalpies, entropies, and Gibbs energies of sublimation, at T = 298.15 K, were derived, and the phase diagram near the triple point coordinates were determined for all isomers. The standard (p(o) = 0.1 MPa) molar enthalpies of combustion of all crystalline isomers were determined, at T = 298.15 K, by static bomb combustion calorimetry. The standard molar enthalpies of formation, in the crystalline and gaseous phases, at T = 298.15 K, were derived. The experimental results for the energetics in the gaseous phase of the three compounds were compared and assessed with the values obtained by ab initio calculations at different levels of theory (DFT and MP2) showing that, at this level of theory, the computational methods underestimate the energetic stability, in the gaseous phase, for these molecules. In order to understand the aromaticity in the central ring of each isomer, calculations of NICS (B3LYP/6-311G++(d,p) level of theory) values on the pyridine ring were also performed.

show abstract

Substituent Effects on the Energetics and Aromaticity of Aminomethylbenzoic Acids

Cited by 20 publications

References 25 publications

From 2-Hydroxypyridine to 4(3H)-Pyrimidinone: Computational Study on the Control of the Tautomeric Equilibrium

From 2-Hydroxypyridine to 4(3H)-Pyrimidinone: Computational Study on the Control of the Tautomeric Equilibrium

Vapor Pressures and Enthalpies of Combustion of the Dihydroxybenzoic Acid Isomers

Energetic and Structural Study of Diphenylpyridine Isomers

Contact Info

Product

Resources

About