ABSTRACT

We determined the standard molar enthalpies of formation in gas-phase, at T=298.15K, of the methyl 2-, 3-, and 4-hydroxybenzoates, through static bomb combustion calorimetry and thermogravimetry. The enthalpies of formation in gas phase were derived from experimental combustion energies and phase-change enthalpies. In addition, we calculated the enthalpies of formation in the gas-phase with the Gaussian G4 composite method combined with atomization reactions and a Boltzmann weighted average to account for the conformational diversity of each compound. Experimental and theoretical determinations differ by less than 2kJ*mol-1. We found that intramolecular hydrogen bonding strongly stabilizes methyl 2-hydroxybenzoate.

Compounds

#	Formula	Name
1	CO2	carbon dioxide
2	H2O	water
3	O2	oxygen
4	C8H8O3	methyl 2-hydroxybenzoate
5	C8H8O3	methyl 3-hydroxybenzoate
6	C8H8O3	methyl 4-hydroxybenzoate

Datasets

The table above is generated from the ThermoML associated json file (link above). POMD and RXND refer to PureOrMixture and Reaction Datasets. The compound numbers are included in properties, variables, and phases, if specificied; the numbers refer to the table of compounds on the left.
Type	Compound-#	Property	Variable	Constraint	Phase	Method	#Points
POMD	4	Normal melting temperature, K ; Crystal			Crystal Liquid Air at 1 atmosphere	DTA	1
POMD	4	Molar enthalpy of transition or fusion, kJ/mol ; Crystal			Crystal Liquid Air at 1 atmosphere	DSC	1
POMD	4	Molar enthalpy of vaporization or sublimation, kJ/mol ; Liquid	Temperature, K; Liquid		Liquid Gas	Derived by Second law	1
POMD	4	Molar heat capacity at constant pressure, J/K/mol ; Liquid	Temperature, K; Liquid	Pressure, kPa; Liquid	Liquid	DSC	20
POMD	5	Normal melting temperature, K ; Crystal			Crystal Liquid Air at 1 atmosphere	DTA	1
POMD	5	Molar enthalpy of transition or fusion, kJ/mol ; Crystal			Crystal Liquid Air at 1 atmosphere	DSC	1
POMD	5	Molar enthalpy of vaporization or sublimation, kJ/mol ; Liquid	Temperature, K; Liquid		Liquid Gas	Derived by Second law	1
POMD	5	Mass density, kg/m3 ; Crystal	Temperature, K; Crystal Pressure, kPa; Crystal		Crystal	Pycnometric method	1
POMD	5	Molar heat capacity at constant pressure, J/K/mol ; Crystal	Temperature, K; Crystal	Pressure, kPa; Crystal	Crystal	DSC	20
POMD	6	Normal melting temperature, K ; Crystal			Crystal Liquid Air at 1 atmosphere	DTA	1
POMD	6	Molar enthalpy of transition or fusion, kJ/mol ; Crystal			Crystal Liquid Air at 1 atmosphere	DSC	1
POMD	6	Molar enthalpy of vaporization or sublimation, kJ/mol ; Liquid	Temperature, K; Liquid		Liquid Gas	Derived by Second law	1
POMD	6	Molar heat capacity at constant pressure, J/K/mol ; Crystal	Temperature, K; Crystal	Pressure, kPa; Crystal	Crystal	DSC	20
RXND	4 1 2 3	Specific internal energy of reaction at constant volume, J/g				Static bomb calorimetry	1
RXND	5 1 2 3	Specific internal energy of reaction at constant volume, J/g				Static bomb calorimetry	1
RXND	6 1 2 3	Specific internal energy of reaction at constant volume, J/g				Static bomb calorimetry	1

Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

Experimental and theoretical study of methyl n-hydroxybenzoates

Ledo, J. Manuel, Flores, Henoc, Solano-Altamirano, J.M., Ramos, Fernando, Hernandez-Perez, Julio M., Camarillo, E. Adriana, Rabell, Brenda, Amador, M. Patricia

ABSTRACT