Combine 90 mL of acetone, 10 mL of chloroform and 2 g of potassium hydroxide, stir the mixture vigorously at -5°C for 2h. After which the suspension was filtered, the filter needs to be washed with acetone, then distill at 60°C until the weight of the solution remains constant. Then pour the chlorobutanol into a bigger beaker and add 100 mL of ice-cold water. Filter and store the filtered sludge. Recrystallize in ethanol to get pure solid chlorobutanol hemihydrate crystals.