Preparation of ethyl boric acid
to a ground round bottomed flask hang of 20 g of boric acid and 200 ml of conc. sulfuric acid (excess acid ensures the bound water, which would otherwise lay emerging ester), fit the reflux condenser. Connect cooling, let the water through the radiator and pour 65 ml of ethanol - the content becomes cloudy and warm up spontaneously. With heating nest maintain 90 minutes in simmering. Then replace condenser for downward and collect the distillate in the range of 70-80 ° C (azeotrope contains 29-32% triethylborátu neck T sub> = 76.6 ° C. Thus prepared product initially burns with a blue flame (ethanol), and then green (ethyl ester of boric kseliny).
fraction accumulated in the range of 105-125 ° C (T var = 117-120 ° C - pure product).
H3BO3 + 3CH3CH2OH --> B(OCH2CH3)3 + 3H2O
Triethylester boric acid is a clear liquid of boiling point 117-120 ° C. Mixes with unlimited alcohol, burning green flames. Water is decomposed back to boric acid and ethanol.