In a three-necked flask equipped with a thermometer, condenser tube and electric stirrer, add a certain material quantity ratio of 2,5-difluoro-3-methylbenzaldehyde and hydroxylamine hydrochloride, heat to maintain 70 ~ 75 , the reaction for 30min, and then slowly add 20 (mass fraction) of aqueous sodium carbonate solution stirring, there are bubbles produced (available lime water test). When the reaction slows down, adjust the pH to 8 ~ 9, stop adding sodium carbonate aqueous solution. Continue to stir, there is a light red precipitate appeared, let stand, until the light red color gradually become milky white. The precipitate was filtered out, washed with water for 2-3 times, dried, obtained milky white solid powder 2,5-difluoro-3-methylbenzaldehyde oxime, weighed for use. 2,5-Difluoro-3-methylbenzaldehyde oxime and acetic anhydride were added to a three-mouth flask according to the ratio of a certain amount of substances, heated to 110-120 , the reaction was 3h, the reaction solution was light orange liquid, cooled down the temperature, left to stand, there were white crystals appeared. Filtering, to get the crystals, dissolved in alcohol, hot filtration to remove insoluble material, filtrate water extraction separation, to get clean colorless needle crystals, low temperature drying, to get 2,5-difluoro-3-methylbenzonitrile.
