Evidence of an odd–even effect on the thermodynamic parameters of odd fluorotelomer alcohols

A phase transition study, including vapour pressure determinations of odd fluorotelomer alcohols {oFTOH; CF3(CF2)nCH2OH, with n = 5 to 9}, is reported in order to explore the effect of the successive introduction of –CF2– groups into the molecule on the thermodynamic properties related to (solid + liquid, solid + gas, and liquid + gas) equilibria. An odd–even effect on the thermodynamic parameters of fusion and sublimation was observed in the homologous series of odd fluorotelomer alcohols indicating an increase of the stability in the crystal packing for the members with an odd number of carbon atoms. The vaporization parameters of o-FTOH were compared with the literature data for their alkane analogues and the results showed a higher volatility of liquid fluorotelomer alcohols than their congeners. The higher molecular conformation restriction of perfluorinated alcohols and/or the higher molar mass seems to contribute to their higher entropy of vaporization which drives the volatility of the 1H,1H-perfluorinated alcohols.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Phase transition study of odd fluorotelomer alcohols series. ► Odd–even effect in the thermodynamic parameters of sublimation and fusion. ► Higher volatility of liquid odd fluorotelomer alcohols than alkane analogues. ► Vapour pressure of 1H,1H-perfluoroalcohols, oFTOH; CF3(CF2)nCH2OH, n = 5 to 9. ► Triple point coordinates of 1H,1H-perfluoroalcohols.