Chain Length Dependence of the Thermodynamic Properties of n-Alkanes and their Monosubstituted Derivatives

• Type: Article in International Scientific Journal
• Date: 2018

Authors

José C. S. Costa (Author) FCUP; Adélio Mendes (Author) FEUP; Luís M. N. B. F. Santos (Author) Other

Journal

Title: Journal of Chemical & Engineering Data

Vol. 63 No. 1

Pages: 1-20

ISSN: 0021-9568

Publisher: American Chemical Society

Indexing

ISI Web of Knowledge - 43 Citations

Scopus - 45 Citations

Associated Projects

LEPABE - Laboratório de Engenharia de Processos, Ambiente, Biotecnologia e Energia

LEPABE-2-ECO-INNOVATION - LEPABE-2-ECO-INNOVATION

Other information

Authenticus ID: P-00N-GT9

DOI: 10.1021/acs.jced.7b00837

Abstract (EN): The present work presents an extensive literature survey and analysis of the heat capacity and thermodynamic properties of fusion, vaporization, and sublimation for the linear hydrocarbons and several terminally substituted homologous series. The successive introduction of methylene groups on the relative stability of the solid and liquid phases is analyzed and discussed based on the chain length dependence of the enthalpies, entropies, and Gibbs energies of phase transition. An oddeven alternation is observed in the fusion and sublimation equilibria. The improved packing patterns of even-numbered n-alkanes is reflected in higher values of melting temperatures and thermodynamic properties of phase transition. Molar heat capacities in liquid phase of n-alkanes derivatives exhibit a linear dependence with the chain length by an increment of 31 +/- 2 JK(-1)mol(-1) per methylene group (-CH2-). A contribution of 4.95 kJmol(-1) per methylene group (value corrected for 298.15 K) is derived for the increment of the enthalpy of vaporization. A constant value for the specific enthalpy of vaporization is observed for long chain compounds: 360 Jg(1). As predictable, the enthalpy of vaporization is higher for groups that can form hydrogen-bonding interactions than for plain hydrocarbons. Concerning the monohalogenated alkanes, a clear increasing of enthalpy of vaporization for the larger halogen groups is observed. Moreover, the thermodynamic results indicate that along the fusion of n-alkanes and n-alkanols, there is a decrease of around 40% in the magnitude of intermolecular interactions.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 20