Aggregation behavior of fluorooctanols in hydrocarbon solvents

The association behaviors of three 1-octanols (1-octanol: C8OH; 1,1,2,2-tetrahydrotridecafluorooctanol TFC8OH; and 1,1-dihydropentadecafluorooctanol: DFC8OH) in two hydrocarbon solvents (n-hexane and benzene) were examined by vibration spectroscopy from 288.15 to 318.15 K. From the analysis of results with a mass action model, it was found that dimers and tetramers of 1-octanols coexisted with monomers in the n-hexane solution. These aggregates were formed by hydrogen bonding between the OH groups of 1-octanols. In the n-hexane solutions, an increase in the fluorination number of the 1-octanol molecule enhanced the intermolecular hydrogen bonding between the OH groups, but reduced the amounts of polymeric species. Conversely, in the benzene solution, the NIR experiment suggested that the OH groups of 1-octanols did not interact with other OH groups, but with the benzene molecules instead. It was found from ¹⁹F NMR chemical shift measurements that the fluorooctanols in the benzene solution aggregated by interaction between the fluorocarbon chains instead of by hydrogen bonding.