Measurement and Prediction of the Monocarboxylic Acids Thermochemical Properties

Abstract

The standard molar enthalpies of vaporization ∆ l g H°m or sublimation ∆ cr g H°m of 2-methylpropanoic, butanoic, 2-methylbutanoic, 3-methylbutanoic, pentanoic, 2,2-dimethylpropanoic, 3,3-dimethylbutanoic, hexanoic, heptanoic, and octanoic acids were measured by the transpiration method. The enthalpies of vaporization ∆ l g H°m of ethanoic, propanoic, 2-methylpropanoic, and butanoic acids were measured using correlation gas chromatography. The enthalpies of the phase transitions of 2,2-dimethylpropanoic acid were measured using differential scanning calorimetry. The values of ∆ l g H°m of the compounds studied were taken as a basis for the development of a group-additivity predictive scheme. The standard molar enthalpies of formation ∆ f H°m(g) at the temperature T ) 298.15 K of monocarboxylic acids were derived using the data for ∆ f H°m(l or cr) from the literature and the present results for the enthalpies of vaporization or sublimation. The improved group-contribution method was used for the estimation of the gaseous enthalpies of formation of monocarboxylic acids.

Vapour pressures and enthalpies of vaporization of a series of the linear n-alkyl acetates

“…Samples of n-alkyl acetates C 8 -C 16 Biochemistry, Academy of Science in Prague. The degree of purity was controlled using a Hewlett-Packard gas chromatograph 5890 Series II equipped with a flame ionization detector and a Hewlett-Packard 3390A integrator.…”

“…Vapour pressures and enthalpies of vaporization of acetates were determined using the method of transpiration in a saturated N 2 -stream [11,16] and applying the Clausius-Clapeyron equation. About 0.5 g of the sample was mixed with glass beads and placed in a thermostatted U-shaped tube having a length of 20 cm and a diameter of 0.5 cm.…”

“…retention times measured on a non-polar capillary column [1,2]. We have contributed to this series of required thermophysical data in the past by determining vapour pressures and enthalpies of vaporization investigations on branched esters [3,4], amines [5], nitro-compounds [6], nitriles [7,8], alcohols - [9][10][11], aldehydes [12], ketones [13], imines [14], fluoroalkanes [15], carboxylic acids [16], and alkyl ethers, acetals, ketals, orthoesters [17][18][19]. This paper extends our previous [2][3][4] studies on the esters with the systematic study of aliphatic acetates C 8 -C 16 .…”

Vapour pressures and enthalpies of vaporization of a series of the linear n-alkyl-benzenes

“…Vapour pressures and enthalpies of vaporization of alkyl-benzenes were determined using the method of transpiration in a saturated N 2 -stream [9,14] and applying the Clausius-Clapeyron equation. About 0.5 g of the sample was mixed with glass beads and placed in a thermostatted U-shaped tube having a length of 20 cm and a diameter of 0.5 cm.…”

“…This paper is another in the series of papers concerning the systematic investigation of vapour pressures of homologues. We have contributed to this series in the past by determining vapour pressures and enthalpies of vaporization investigations on branched esters [1,2], amines [3], nitro-compounds [4], nitriles [5,6], alcohols [7,8], aldehydes [9], ketones [10], imines [11], fluoroalkanes [12], carboxylic acids [13], and alkyl ethers, acetals, ketals, orthoesters [14][15][16][17]. This work was initiated to investigate the relationship between vaporization enthalpy and Kovat's indices and it extends our previous [18,19] studies on the alkyl-benzenes with the systematic study of the linear alkyl-benzenes with the alkyl chain length of C 5 , C 7 , C 10 , and C 11 .…”