Thermodynamic properties of sublimation of the ortho and meta isomers of acetoxy and acetamido benzoic acids. (July 2015)

• Record Type: Journal Article
• Authors: Almeida, Ana R.R.P.; Sousa, Carlos A.D.; Santos, Luís M.N.B.F.; Monte, Manuel J.S.
• Is Part Of: Journal of chemical thermodynamics. Volume 86(2015:Jul.)
• Page Start: 6
• Page End: 12
• Publication Date: 2015-07
• Subjects: Acetoxybenzoic acid -- Acetamidobenzoic acid -- Vapour pressure -- Sublimation -- Thermodynamic properties -- Aspirin; Thermodynamics -- Periodicals; Thermochemistry -- Periodicals; Thermodynamique -- Périodiques; Thermochimie -- Périodiques; Thermochemistry; Thermodynamics; Periodicals; 541.369
• DOI: 10.1016/j.jct.2015.02.010
• Languages: English
• ISSNs: 0021-9614

Abstract

Graphical abstract: Highlights: Vapour pressures of ortho and meta acetoxy and acetamido benzoic acids are reported. Results of temperatures and enthalpies of fusion are presented. Standard molar Δ H, Δ S and Δ G of sublimation were derived. Correlations for estimating vapour pressures are presented. Abstract: This paper reports vapour pressures measured at several different temperatures using the Knudsen effusion method of ortho -acetoxybenzoic acid (aspirin) (341.1 to 361.1) K, meta -acetoxybenzoic acid (344.2 to 362.2) K, ortho -acetamidobenzoic acid (367.2 to 389.2) K, and meta -acetamidobenzoic acid (423.2 to 441.1) K. The experimental results enabled the determination of the standard molar enthalpies, entropies and Gibbs energies of sublimation, at T = 298.15 K, of the four compounds studied. DSC experiments yield results of the temperature and enthalpy of fusion. The experimental results were compared with literature ones for the para isomers of the acids acetoxybenzoic and acetamidobenzoic. Correlations involving temperature of fusion, and standard molar enthalpy and Gibbs energy of sublimation of several substituted benzoic acids were proposed. Those correlation equations allow a good estimative of volatility of benzoic acid derivatives from their enthalpies of sublimation and temperatures of fusion.