Reactions of Methyl Perfluoroalkyl Ethers with Isopropyl Alcohol: Experimental and Theoretical Studies

The reaction of an isomeric mixture of the methyl perfluoroalkyl ether, C₄F₉OCH₃ (Novec-7100), in the presence of isopropyl alcohol (IPA) and/or water has been studied by measuring the rate of product formation using an ion-selective electrode (ISE) for fluoride ion, Karl Fisher coulometric titrations for water, and ¹H and ¹⁹F NMR spectroscopy for product identification and rate studies. The results showed the methyl perfluoroalkyl ether to be very stable with products forming at the rate of ∼1 ppm per year at a laboratory temperature of 20 °C. Measurements over the temperature range of 6° to 100 °C were made on samples aged for periods up to 1.8 years. Density functional theory calculations (DFT, <i>B3LYP/6-31+G­(d)</i>) were employed to investigate different reaction pathways and formulate the probable reaction mechanism. The experimental enthalpy (Δ<i>H</i>^⧧) and entropy (Δ<i>S</i>^⧧) of activation were determined based on several different kinetic measurements. The Δ<i>H</i>^⧧ values are in the range of 20–25 kcal/mol and the corresponding Δ<i>S</i>^⧧ values range from −32 to −15 cal/(mol K). These are in good agreement with the theoretical values. While the range of Δ<i>H</i>^⧧ values does not change appreciatively, the Δ<i>S</i>^⧧ values are dependent on the proportion of vapor to liquid involved in the reaction of C₄F₉OCH₃ with IPA so that the more vapor the more negative the Δ<i>S</i>^⧧ value