[duubs]

Let's say I was doing a fischer esterification and I distilled my product which has an aqueous layer still present and that aqueous layer had the same amount of volume as that of my ester. Why would I get the exact same thing on the other end of the distillation tube, with no change in vapour temperature between impurities? Basically, the impurities boiled out with the ester and I'm 100% sure that my product was quite pure. Why? Also, I used 5% sodium bicarbonate to neutralize the acids. Is it possible that the sodium bicarbonate hydrolyzed the ester? I can't see a way it could even react with the ester.

[Babcock_Hall]

I am not sure about everything you ask, but I find it quite unlikely that sodium bicarbonate will hydrolyze the ester.  A strong base is another matter.

[duubs]

This may sound far fetched, but do you think that since water has such a large heat capacity, it easily transferred the heat energy needed to evaporate the ester(isopentyl acetate), and so there were actual pockets of increased heat vapours but the thermometer read only the average temperature between the aqueous layer and organic layer.

[discodermolide]

I think water and isopentyl acetate form a binary azeotrope with BPt. 94°C.
see http://www.media.rmutt.ac.th/media/e-book/engineer/Chemistry/Handbook%20of%20Chemistry%20and%20Physics/Section%2006/06_35_86.pdf

[duubs]

Awesome, that's the answer I was looking for. Thank you very much