Abstract:The standard (p°) 0.1 MPa) molar enthalpies of formation for gaseous pyridine-2,5-dicarboxylic acid, pyridine-2,6-dicarboxylic acid, and dimethylpyridine-2,6-dicarboxylate were derived from the standard molar enthalpies of combustion, in oxygen, at T ) 298.15 K, measured by static bomb combustion calorimetry, and the standard molar enthalpies of sublimation, at 298.15 K, measured by Calvet microcalorimetry: pyridine-2,5-dicarboxylic acid, -(580.6 ( 5.0) kJ‚mol -1 ; pyridine-2,6-dicarboxylic acid, -(608.0 ( 6.1… Show more
“…Recently, Roux et al 35 reported an enthalpic increment of (18.0 ( 4.6) kJ‚mol -1 for the methylation of benzoic acid, which is in good agreement with the increment for the dimethylation of pyridine-2,6-dicarboxylic acid. 12 The present results point to a similar increment for the methylation of 4-pyridine carboxylic acid and to a higher increment for the methylation of 2-pyridine carboxylic acid. This should reflect the effect of the intramolecular hydrogen bond in 2-pyridine carboxylic acid described by Shahawy et al 36 on the basis of theoretical SCF-CI calculations.…”
Section: Resultssupporting
confidence: 82%
“…In this context, systematic experimental and theoretical thermochemical studies on heterocyclic molecules derived from pyridine have been done in our Thermochemistry Laboratory for more than a decade in order to evaluate the energetic effects of different substituents on the pyridinic ring. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] The main goal of the present work is to determine the gaseous enthalpies of formation of methyl picolinate (2-PyCOOCH 3 ), methyl nicotinate (3-PyCOOCH 3 ), and methyl isonicotinate (4-PyCOOCH 3 ), represented in Figure 1, together with the measurement of other relevant properties to the thermodynamic characterization of those isomers.…”
The present work reports the values of the standard (p°) 0.1 MPa) molar energies of combustion for the liquid isomers methyl picolinate and methyl isonicotinate and for the crystalline isomer methyl nicotinate measured by static bomb calorimetry. The molar enthalpies of vaporization of the three isomers at T ) 298.15 K as well as the molar enthalpies of sublimation of two of them (methyl picolinate and methyl nicotinate) were derived from vapor pressure measurements at different temperatures using a static method. The molar enthalpies of vaporization at T ) 298.15 K of methyl picolinate and methyl isonicotinate were also measured using Calvet microcalorimetry. The thermal behavior of the compounds was studied by differential scanning calorimetry, and the temperatures and the molar enthalpies of fusion were determined using this technique. The experimental results were used to derive the gaseous standard molar enthalpies of formation, at 298.15 K, of the three pyridinecarboxylic acid methyl ester isomers and the triple points of the ortho and meta isomers.
“…Recently, Roux et al 35 reported an enthalpic increment of (18.0 ( 4.6) kJ‚mol -1 for the methylation of benzoic acid, which is in good agreement with the increment for the dimethylation of pyridine-2,6-dicarboxylic acid. 12 The present results point to a similar increment for the methylation of 4-pyridine carboxylic acid and to a higher increment for the methylation of 2-pyridine carboxylic acid. This should reflect the effect of the intramolecular hydrogen bond in 2-pyridine carboxylic acid described by Shahawy et al 36 on the basis of theoretical SCF-CI calculations.…”
Section: Resultssupporting
confidence: 82%
“…In this context, systematic experimental and theoretical thermochemical studies on heterocyclic molecules derived from pyridine have been done in our Thermochemistry Laboratory for more than a decade in order to evaluate the energetic effects of different substituents on the pyridinic ring. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] The main goal of the present work is to determine the gaseous enthalpies of formation of methyl picolinate (2-PyCOOCH 3 ), methyl nicotinate (3-PyCOOCH 3 ), and methyl isonicotinate (4-PyCOOCH 3 ), represented in Figure 1, together with the measurement of other relevant properties to the thermodynamic characterization of those isomers.…”
The present work reports the values of the standard (p°) 0.1 MPa) molar energies of combustion for the liquid isomers methyl picolinate and methyl isonicotinate and for the crystalline isomer methyl nicotinate measured by static bomb calorimetry. The molar enthalpies of vaporization of the three isomers at T ) 298.15 K as well as the molar enthalpies of sublimation of two of them (methyl picolinate and methyl nicotinate) were derived from vapor pressure measurements at different temperatures using a static method. The molar enthalpies of vaporization at T ) 298.15 K of methyl picolinate and methyl isonicotinate were also measured using Calvet microcalorimetry. The thermal behavior of the compounds was studied by differential scanning calorimetry, and the temperatures and the molar enthalpies of fusion were determined using this technique. The experimental results were used to derive the gaseous standard molar enthalpies of formation, at 298.15 K, of the three pyridinecarboxylic acid methyl ester isomers and the triple points of the ortho and meta isomers.
“…What are the relative stabilities of the isomeric diacetylpyridines? Is it the same order as recently found for the related pyridinedicarboxylic acids [84] wherein COOH replaces COCH 3 ?…”
In the current review the content of the journal Structural Chemistry for the calendar year 2010 is related to thermochemistry. To a short summary of each article in this volume of the journal a thermochemical comment is added.
“…The structure of this zinc(II) complex revealed the peculiarity of having the ethylenediamine ligand acting in a very unusual way as a bridge. The enthalpy of formation of dipicolinic acid has been recently determined as well as its 2,3-and 2,5-isomers [110].…”
Section: Issuementioning
confidence: 99%
“…We wonder what is the case for the isomeric pyridine-3,4-dicarboxylate chelate derivative? Comparison between the 2,3-and 3,4-diacids has surprisingly been lacking: for example, the enthalpy of formation of only the former has been measured [110].…”
In the current review paper the content of the journal Structural Chemistry for the calendar year 2008 is related to thermochemistry. Papers are summarized and a thermochemical slant added. Often questions are asked and research topics suggested.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.