Doing an esterification practical in my Matric chem class today, we noticed that when the sulphuric acid was added to the mixture of 3-methylbutanol and ethanoic acid, the liquid around the boiling chips or glass beads (there were examples of each with the same result)became coloured browny-orange. Apparantly none of the chem teachers at our school can explain why this would happen, but it was happening consistently. Once the ester was distilled at the end of the procedure, the colour stayed with any ester that was undistilled. Can anyone explain why this would happen? Thanks.