The reaction of pyridine, acetic anhydride, water and citric acid is used as a colorimetric identifier of citric acid. What reactions occur and why does the color change from colorless to greenish? I have been looking everywhere for the answer and have, so far, come up with nothing.
The reaction is made from 1 ml of water containing citric acid, 1.3 ml of pyridine which is then mixed and then 5.7 ml of acetic anhydride is added. Then it is left in a water bath with a temperature of 32 degrees celsius.