n an reaction between 2,3-dimethyl-1,3-butadiene with maleic anhydride, I had to wash the product repeatedly with 2 mL of water, each time removing the supernatant fluid that resulted. This had to be done until the wash fluid that I removed after each wash registered as not acidic on a Congo red test paper. The product was then recrystallized, etc.
What was the purpose of the wash? Why was it necessary to make the product less acidic?