Impact of configuration and fluorination on the solubility of octyl ester benzoate dimers in CO2 |
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| Institution: | 1. Department of Chemical and Life Science Engineering, Virginia Commonwealth University, 601 West Main Street, Richmond, VA 23284, USA;2. Department of Chemistry, Virginia Commonwealth University, Richmond, VA 23284, USA;3. Research Department, Chemistry Division, NAWCWD-US NAVY, China Lake, CA 93555, USA;1. Laboratoire des Interfaces et Matériaux Avancés, Faculté des Sciences de Monastir, Université de Monastir, 5000 Monastir, Tunisia;2. Laboratoire d’Automatique et de Génie des Procédés, UMR 5007 CNRS, Université Lyon 1, 43 bd 11 Novembre, 69622 Villeurbanne, France;3. Laboratoire des Méthodes et Techniques d’Analyse, INRAP, BioTechpôle Sidi-Thabet, 2020 Sidi-Thabet, Tunisia;4. Institut des Sciences Analytiques, UMR CNRS 5180, Université Lyon 1, 43 bd 11 Novembre, 69622 Villeurbanne, France;1. Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, College of Materials Science and Chemical Engineering, Harbin Engineering University, Harbin 150001, China;2. Fundamental Science on Nuclear Safety and Simulation Technology Laboratory, Harbin Engineering University, Harbin 150001, China |
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| Abstract: | Data are reported on the phase behavior of hydrocarbon and semifluoroinated octyl ester benzoate dimers in CO2 to temperatures of 100 °C and pressures of 1 600 bar. The experimental data at 75 °C demonstrate that the non-fluorinated head-to-head (H–H) dimer dissolves in CO2 at ∼400 bar lower pressures than the non-fluorinated tail-to-tail (T–T) dimer. Even though partially fluorinating the octyl tails of the H–H and T–T dimers renders them soluble in CO2 at pressures near 200 bar, it still takes ∼40 bar more pressure to dissolve the fluorinated T–T dimer as compared to the H–H dimer. The difference in pressures needed to dissolve these dimers is attributed to steric constraints on the coplanarity of the benzene rings imposed by the H–H regiochemistry that do not exist with T–T dimers. Semi-empirical quantum mechanics calculations suggest that the H–H dimer has a twisted, non-coplanar conformation due to the steric effect of the octyl ester groups while the T–T dimer has a less twisted conformation. Steric hindrance in the H–H dimer reduces considerably resonance or conjugation between the π electrons of the aromatic groups which also reduces the dipole moments of the H–H dimers compared to those of the T–T dimers. |
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