Synthesis of Fluorinated Dimethyl Carbonates by Direct Fluorination

Abstract

Growing interest has been focused on the development of fluorinated solvents for lithium batteries, because they have a number of benefits such as excellent oxidation durability, wide liquidus ranges, and nonflammability. Fluorination of dimethyl carbonate (DMC) is carried out using molecular fluorine (15 vol.% F₂/N₂) at 5°C, and the fluorinated derivatives of the DMC are identified and characterized. The selectivity of monofluorinated dimethyl carbonate (MFDMC) is ca. 90% at early stage of the fluorination. The successive electrophilic substitution of a hydrogen with a fluorine is found to proceed for the direct fluorination of the DMC.

Keywords:

• Direct fluorination
• Dimethyl carbonate
• Fluorinated dimethyl carbonate
• Lithium battery

Notes

^aGC‐MS (CI) (m/z): DMC, 91 [M + H]⁺; MFDMC, 109 [M + H]⁺; DFDMC, 127 [M + H]⁺; gem‐DFDMC, 127 [M + H]⁺; TFDMC, 145 [M + H]⁺.

^bGC‐MS (EI) (m/z): DMC, 90 [M]⁺ (11.42), 59 COOCH₃ ⁺ (100), 31 CH₃O⁺ (73.14); MFDMC, 77 COOCH₂F⁺ (4.33), 59 COOCH₃ ⁺ (84.25), 33 CH₂F⁺ (100); DFDMC, 77 COOCH₂F⁺ (15.74), 33 CH₂F⁺ (100); gem‐DFDMC, 95 COOCHF₂ ⁺ (2.38), 59 COOCH₃ ⁺ (30), 51 CHF₂ ⁺ (100), 31 CH₃O⁺ (30.95); TFDMC, 33 CH₂F⁺ (46.27), 51 CHF₂ ⁺ (100), 77 COOCH₂F⁺ (7.05), 95 COOCHF₂ ⁺ (3.52).

^cAnal. Calcd for C₃H₅FO₃: C, 33.3%; H, 4.7%; F, 17.6%. Found: C, 33.4%; H, 3.9%; F, 17.5%.

^{d 1}H NMR (1% TMS/CDCl₃, 500.00 MHz): δ 4.23 (s, 3H), 6.08 (d, ² J _HF = 51.5 Hz, 2H). ¹³C NMR (1% TMS/CDCl₃, 125.65 MHz): δ 55.10, 96.97 (d, ¹ J _CF = 219.0 Hz), 154.68. ⁹F NMR (2% CF₃COOD/D₂O, 470.40 MHz): δ −158.05 (t, ² J _FH = 51.5 Hz).