Chain-Length Dependence of the Thermodynamic Behavior of Homologous alpha,omega-Disubstituted Alkanes

• Type: Another Publication in an International Scientific Journal
• Date: 2019

Authors

Costa, JCS (Author) FCUP; Luis M N B F Santos (Author) FCUP

Journal

Title: Journal of Chemical & Engineering Data

Vol. 64

Pages: 2229-2246

ISSN: 0021-9568

Publisher: American Chemical Society

Indexing

ISI Web of Knowledge - 15 Citations

Scopus - 15 Citations

Other information

Authenticus ID: P-00Q-MC9

DOI: 10.1021/acs.jced.9b00125

Abstract (EN): The chain-length dependence of the thermodynamic properties associated with the solid-to-liquid, liquid-to-gas, and solid-to-gas phase equilibria is analyzed and discussed for homologous families of linear alpha,omega-disubstituted alkanes, R-(CH2)(n)-R series. A remarkable alternation on the melting properties exhibited by even and odd-numbered alkanes is clearly emphasized in their a,w-disubstituted derivatives since the even members display increased properties due to their higher crystal packing density. The odd-even effect is also perceived in the values of Delta H-sub degrees and Delta S-sub degrees. Strong hydrogen bonding contributes to high boiling points and Delta H-vap degrees values evidenced by alkane-alpha,omega-diols. Moreover, the anomalously low values of Delta H-sub degrees and Delta H-vap degrees reported for larger dicarboxylic acids suggest the formation, in the vapor phase, of hydrogen-bonded cyclic structures. Furthermore, the analysis of the Delta H-fus degrees/Delta H-sub degrees and Delta S-sub degrees/Delta S-sub degrees ratios is used to highlight the contribution of functional groups to the cohesive interaction preserved in the liquid phase after a fusion transition. The thermodynamic interpretation indicates a higher structuration in the liquid alkane-alpha,omega-diols and alkane-alpha,omega-dioic acids, which have lower ratios of Delta H-fus degrees/A(sub)H degrees than corresponding n-alkanes. In addition, the thermodynamic analysis supports that hydrogen bonding in the liquid phase of alkanamines or alkane-alpha,omega-diamines has a significant low contribution to the overall intermolecular interactions.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 18