Magnesium powder (14.4 g, 0.6 mol) was put into a four-necked reaction bottle containing 200 ml of methanol, electric stirring was turned on, a large number of bubbles were produced in the bottle, and the temperature was increased to 61C. After 2 h, the solution turned into a milky white suspension. P-toluene (108g, 1.0 mol) was added to the reaction bottle, and after 50 min, methanol started to be evaporated, and when the reaction solution became thick, 200 ml of toluene was made up. Increase the temperature, when the internal temperature reached 95 , add paraformaldehyde (90g, 3.0mol) in batches, the device was changed to a distillation device, evaporation of low-boiling substances, after 30min almost no fraction evaporated, withdraw the distillation device, continue to react for 2.5h, tracked with a TLC dot plate, the reaction of p-methylphenol was complete. Stop heating, wait for the internal temperature to drop to 65C, adjust ph=1 with 18.5% hydrochloric acid. leave to stand and separate the liquid, the organic layer was extracted with 70ml toluene for 2 times, the organic layer was combined, the organic layer was washed with water for 3 times until the ph was close to 7. 2-methyl-4-hydroxybenzaldehyde was obtained.
