ABSTRACT

The Knudsen mass-loss effusion technique was used for measuring the vapor pressures at different temperatures of the following 4-n-alkyloxybenzoic acids: 4-methoxybenzoic acid, between (340 and 362) K; 4-ethoxybenzoic acid, between (349 and 373) K; 4-propoxybenzoic acid, between (345 and 365) K; 4-butoxybenzoic acid, between (351 and 373) K; 4-pentyloxybenzoic acid, between (355 and 377) K; 4-hexyloxybenzoic acid, between (363 and 379) K; 4-heptyloxybenzoic acid, between (355 and 361) K; and 4-octyloxybenzoic acid, between (363 and 372) K. From the temperature dependence of the vapor pressure of each crystalline compound, the standard (po = 105 Pa) molar enthalpies and Gibbs energies of sublimation, at T = 298.15 K, were derived. Differential scanning calorimetry was used in the study of phase transitions between condensed phases. The measured thermodynamic properties are compared with the results obtained on a previous similar study concerning the 4-n-alkylbenzoic acids series.

Compounds

#	Formula	Name
1	C8H8O3	4-methoxybenzoic acid
2	C9H10O3	4-ethoxybenzoic acid
3	C10H12O3	4-propyloxybenzoic acid
4	C11H14O3	4-butoxybenzoic acid
5	C12H16O3	4-n-pentyloxybenzoic acid
6	C14H20O3	4-heptyloxybenzoic acid
7	C13H18O3	4-n-hexyloxybenzoic acid
8	C15H22O3	4-n-octyloxybenzoic acid

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	Phase	Method	#Points
POMD	1	Molar enthalpy of transition or fusion, kJ/mol ; Crystal		Crystal Liquid Air at 1 atmosphere	DSC	1
POMD	1	Triple point temperature, K ; Crystal		Crystal Liquid Air at 1 atmosphere	DTA	1
POMD	1	Vapor or sublimation pressure, kPa ; Crystal	Temperature, K; Crystal	Crystal Gas	Calculated from knudsen effusion weight loss	36
POMD	2	Molar enthalpy of transition or fusion, kJ/mol ; Crystal		Crystal Liquid Air at 1 atmosphere	DSC	1
POMD	2	Triple point temperature, K ; Crystal		Crystal Liquid Air at 1 atmosphere	DTA	1
POMD	2	Vapor or sublimation pressure, kPa ; Crystal	Temperature, K; Crystal	Crystal Gas	Calculated from knudsen effusion weight loss	39
POMD	3	Molar enthalpy of transition or fusion, kJ/mol ; Nematic liquid crystal		Nematic liquid crystal Liquid Air at 1 atmosphere	DSC	1
POMD	3	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 1		Crystal 1 Nematic liquid crystal Air at 1 atmosphere	DSC	1
POMD	3	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 2		Crystal 2 Crystal 1 Air at 1 atmosphere	DSC	1
POMD	3	Triple point temperature, K ; Crystal 2		Crystal 2 Crystal 1 Air at 1 atmosphere	DTA	1
POMD	3	Triple point temperature, K ; Crystal 1		Crystal 1 Nematic liquid crystal Air at 1 atmosphere	DTA	1
POMD	3	Triple point temperature, K ; Nematic liquid crystal		Nematic liquid crystal Liquid Air at 1 atmosphere	DTA	1
POMD	3	Vapor or sublimation pressure, kPa ; Crystal 2	Temperature, K; Crystal 2	Crystal 2 Gas	Calculated from knudsen effusion weight loss	32
POMD	4	Molar enthalpy of transition or fusion, kJ/mol ; Nematic liquid crystal		Nematic liquid crystal Liquid Air at 1 atmosphere	DSC	1
POMD	4	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 1		Crystal 1 Nematic liquid crystal Air at 1 atmosphere	DSC	1
POMD	4	Triple point temperature, K ; Crystal		Crystal Nematic liquid crystal Air at 1 atmosphere	DTA	1
POMD	4	Triple point temperature, K ; Nematic liquid crystal		Nematic liquid crystal Liquid Air at 1 atmosphere	DTA	1
POMD	4	Vapor or sublimation pressure, kPa ; Crystal	Temperature, K; Crystal	Crystal Gas	Calculated from knudsen effusion weight loss	35
POMD	5	Molar enthalpy of transition or fusion, kJ/mol ; Nematic liquid crystal		Nematic liquid crystal Liquid Air at 1 atmosphere	DSC	1
POMD	5	Molar enthalpy of transition or fusion, kJ/mol ; Crystal		Crystal Nematic liquid crystal Air at 1 atmosphere	DSC	1
POMD	5	Triple point temperature, K ; Crystal		Crystal Nematic liquid crystal Air at 1 atmosphere	DTA	1
POMD	5	Triple point temperature, K ; Nematic liquid crystal		Nematic liquid crystal Liquid Air at 1 atmosphere	DTA	1
POMD	5	Vapor or sublimation pressure, kPa ; Crystal	Temperature, K; Crystal	Crystal Gas	Calculated from knudsen effusion weight loss	36
POMD	6	Molar enthalpy of transition or fusion, kJ/mol ; Nematic liquid crystal		Nematic liquid crystal Liquid Air at 1 atmosphere	DSC	1
POMD	6	Molar enthalpy of transition or fusion, kJ/mol ; Smectic liquid crystal		Smectic liquid crystal Nematic liquid crystal Air at 1 atmosphere	DSC	1
POMD	6	Molar enthalpy of transition or fusion, kJ/mol ; Crystal		Crystal Smectic liquid crystal Air at 1 atmosphere	DSC	1
POMD	6	Triple point temperature, K ; Crystal		Crystal Smectic liquid crystal Air at 1 atmosphere	DTA	1
POMD	6	Triple point temperature, K ; Smectic liquid crystal		Smectic liquid crystal Nematic liquid crystal Air at 1 atmosphere	DTA	1
POMD	6	Triple point temperature, K ; Nematic liquid crystal		Nematic liquid crystal Liquid Air at 1 atmosphere	DTA	1
POMD	6	Vapor or sublimation pressure, kPa ; Crystal	Temperature, K; Crystal	Crystal Gas	Calculated from knudsen effusion weight loss	35
POMD	7	Molar enthalpy of transition or fusion, kJ/mol ; Nematic liquid crystal		Nematic liquid crystal Liquid Air at 1 atmosphere	DSC	1
POMD	7	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 1		Crystal 1 Nematic liquid crystal Air at 1 atmosphere	DSC	1
POMD	7	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 2		Crystal 2 Crystal 1 Air at 1 atmosphere	DSC	1
POMD	7	Triple point temperature, K ; Crystal 2		Crystal 2 Crystal 1 Air at 1 atmosphere	DTA	1
POMD	7	Triple point temperature, K ; Crystal 1		Crystal 1 Nematic liquid crystal Air at 1 atmosphere	DTA	1
POMD	7	Triple point temperature, K ; Nematic liquid crystal		Nematic liquid crystal Liquid Air at 1 atmosphere	DTA	1
POMD	7	Vapor or sublimation pressure, kPa ; Crystal 1	Temperature, K; Crystal 1	Crystal 1 Gas	Calculated from knudsen effusion weight loss	26
POMD	8	Molar enthalpy of transition or fusion, kJ/mol ; Nematic liquid crystal		Nematic liquid crystal Liquid Air at 1 atmosphere	DSC	1
POMD	8	Molar enthalpy of transition or fusion, kJ/mol ; Smectic liquid crystal		Smectic liquid crystal Nematic liquid crystal Air at 1 atmosphere	DSC	1
POMD	8	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 1		Crystal 1 Smectic liquid crystal Air at 1 atmosphere	DSC	1
POMD	8	Molar enthalpy of transition or fusion, kJ/mol ; Crystal 2		Crystal 2 Crystal 1 Air at 1 atmosphere	DSC	1
POMD	8	Triple point temperature, K ; Crystal 2		Crystal 2 Crystal 1 Air at 1 atmosphere	DTA	1
POMD	8	Triple point temperature, K ; Nematic liquid crystal		Nematic liquid crystal Liquid Air at 1 atmosphere	DTA	1
POMD	8	Triple point temperature, K ; Crystal 1		Crystal 1 Smectic liquid crystal Air at 1 atmosphere	DTA	1
POMD	8	Triple point temperature, K ; Smectic liquid crystal		Smectic liquid crystal Nematic liquid crystal Air at 1 atmosphere	DTA	1
POMD	8	Vapor or sublimation pressure, kPa ; Crystal 1	Temperature, K; Crystal 1	Crystal 1 Gas	Calculated from knudsen effusion weight loss	29

Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

Thermodynamic Study of 4-n-Alkyloxybenzoic Acids

Fonseca, J. M. S.[Jose M.S.], Santos, L. M. N. B. F.[Luis M. N. B. F.], Monte, M. J. S.[Manuel J. S.]

ABSTRACT