I was in a chemistry lecture about the upcoming laboratory practical on esters that I would have to take. My lecturer had mentioned that we ought not worry about "the pink coloration that will occur" during the esterification process. However, when we asked why a color change would even occur, his reply was very vague. According to him, there is a general consensus that no-one knows why.
We will be asked to produce an ester using ethanoic acid, butan-1-ol, and concentrated sulfuric acid, in the presence of boiling chips.
So is there a known answer to the mysterious pink coloration? I think it's due to some contaminants that might be present in the sulfuric acid, but my lecturer says the pink coloration is completely random and that everyone in past few years have always used the same solutions.