Thermodynamic study of phase transitions in methyl esters of ortho- meta- and para-aminobenzoic acids

• Type: Article in International Scientific Journal
• Date: 2012

Authors

Ana R R P Almeida (Author) Other; Manuel J S Monte (Author) FCUP

Journal

Title: Journal of Chemical Thermodynamics

Vol. 53

Pages: 100-107

ISSN: 0021-9614

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 20 Citations

Scopus - 20 Citations

Scientific classification

FOS: Engineering and technology > Mechanical engineering

Other information

Authenticus ID: P-002-5AV

DOI: 10.1016/j.jct.2012.04.006

Abstract (EN): A static method based on capacitance gauges was used to measure the vapor pressures of the condensed phases of the methyl esters of the three aminobenzoic acids. For methyl o-aminobenzoate the vapor pressures of the liquid phase were measured in the range (285.4 to 369.5) K. For the meta and para isomers vapor pressures of both crystalline and liquid phases were measured in the ranges (308.9 to 376.6) K, and (332.9 to 428.0) K, respectively. Vapor pressures of the latter compound were also measured using the Knudsen effusion method in the temperature range (319.1 to 341.2) K. From the dependence of the vapor pressures on the temperature, the standard molar enthalpies and entropies of sublimation and of vaporization were derived. Differential scanning calorimetry was used to measure the temperatures and molar enthalpies of fusion of the three isomers. The results enabled the estimation of the enthalpy of the intermolecular (N-H center dot center dot center dot O) hydrogen bond in the crystalline methyl p-aminobenzoate. A correlation relating the temperature of fusion and the enthalpy and Gibbs energy of sublimation of benzene, methyl benzoates and benzoic acids was derived.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 8