Experimental and Computational Thermochemical Study of alpha-Alanine (DL) and beta-Alanine

• Type: Article in International Scientific Journal
• Date: 2010

Authors

Manuel A V R Ribeiro da Silva (Author) FCUP; Maria das Dores C R Ribeiro da Silva (Author) FCUP; Ana Filipa L O M Santos (Author) FCUP; Maria Victoria Roux (Author) Other; Concepcion Foces Foces (Author) Other; Rafael Notario (Author) Other; Ramon Guzman Mejia (Author) Other; Eusebio Juaristi (Author) Other

Journal

Title: Journal of Physical Chemistry B

Vol. 114 No. 1

Pages: 16471-16480

ISSN: 1520-6106

Publisher: American Chemical Society

Indexing

ISI Web of Knowledge - 27 Citations

Scopus - 29 Citations

Scientific classification

FOS: Natural sciences > Chemical sciences

Other information

Authenticus ID: P-003-020

DOI: 10.1021/jp106824e

Abstract (EN): This paper reports an experimental and theoretical study of the gas phase standard (p(o) = 0.1 MPa) molar enthalpies of formation, at T = 298.15 K, of alpha-alanine (DL) and beta-alanine. The standard (p(o) = 0.1 MPa) molar enthalpies of formation of crystalline alpha-alanine (DL) and beta-alanine were calculated from the standard molar energies of combustion, in oxygen, to yield CO2(g), N-2(g), and H2O(l), measured by static-bomb combustion calorimetry at T = 298.15 K. The vapor pressures of both amino acids were measured as function of temperature by the Knudsen effusion mass-loss technique. The standard molar enthalpies of sublimation at T = 298.15 K was derived from the Clausius-Clapeyron equation. The experimental values were used to calculate the standard (p(o) = 0.1 MPa) enthalpy of formation of alpha-alanine (DL) and beta-alanine in the gaseous phase, Delta H-f(m)o(g), as -426.3 +/- 2.9 and -421.2 +/- 1.9 kJ.mol(-1), respectively. Standard ab initio molecular orbital calculations at the G3 level were performed. Enthalpies of formation, using atomization reactions, were calculated and compared with experimental data. Detailed inspections of the molecular and electronic structures of the compounds studied were carried out.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 10