1) Esterification reaction:
Methyl 2-hydroxyisobutyrate (20.1g, 0.17mol) was added to the reactor, stirred, and cooled to -10～-5℃. Then, the temperature was controlled at -10～-5℃, and thionyl chloride (36.4g, 0.31mol) was added dropwise. After the addition was complete, the mixture was stirred for 3h. GC detection showed that the reaction of the starting material methyl 2-hydroxyisobutyrate was complete, and the reaction was stopped;
2) Fluorination reaction:
Cool the reactor to -15 to -20°C, then add hydrogen fluoride (37.4 g, 1.87 mol) and triethylamine (0.7 g, 6.80 mmol). Add the liquid obtained in step 1) to the reactor, stop cooling, slowly raise the temperature, and stir the reaction at 40 to 45°C for 3 to 5 hours. GC analysis shows that the reactants have reacted completely, and the reaction is complete.
3) Post-treatment and distillation:
The organic phase in the reaction solution was extracted with ethyl acetate (300 mL × 3). The organic phase was then washed with ethyl acetate and water (50 mL), followed by washing with saturated sodium bicarbonate aqueous solution (50 mL × 2) and water (50 mL). The solution was dried in a desiccator to remove water. Chlorine gas was then introduced into the organic phase. GC analysis showed that the methyl methacrylate content was <0.2 wt.%. The chlorine gas introduction was stopped, and the solution was transferred to a distillation column for vacuum fractionation. The fraction collected at 65–70 °C under 150–160 mmHg was METHYL 2-FLUORO-2-METHYLPROPIONATE, with a GC content of 99.5% and a yield of 79.3%.
