# How slow is a ester reaction without a catalyst? (in a whiskey barrel?)

The typical description of a high school esterification reaction of an alcohol and an organic acid uses a strong acid catalyst like $\ce{H2SO4}$; otherwise the reaction is said to be "slow".

I would like to know, how slow? For context I am interested in the esterification reaction which happen in the time frame of distillation of whiskey and whiskey maturing in a barrel.

New spirit (what goes into a barrel to age and become whiskey) is approximately 60% EtOH, 39% water and less than 1% (I think) other alcohols, and organic acids like acetic and lactic acid.

How long would this system take to come to equilibrium, without any catalyst? (Hours, days, months, years?)

• Please specify the reaction you are interested in: esterification? Ester hydrolysis? Transesterification? Do you have any particular ester in mind? Depending on their chemical structure, esters reactivity can vary greatly. – vapid Jul 27 '16 at 7:27
• @vapid I am interested to know the time frame, to form an equilibrium. So Esterfication would be the main thing but that would be offset by Ester hydrolysis naturally. The the main esters would be Ethyl Acetate and Ethyl Lactate – DarcyThomas Jul 27 '16 at 8:24
• The question is built of several assumption, most important, there is no catalysts present. There are ALWAYS catalysts present! I also, I highly double that the esters are straightforward products of acids and the alcohol present. In most organic matter there are significant amount of esters presents, as well they can be formed during distillation at high temperature. Since boiling point of esters are lower than acids, i would expect them to be actually enriched in any distilled alcohol. – Greg Jul 28 '16 at 6:19
• @Greg There always caveats. However having some ball park of how long would be useful. Is it on the order of hrs, days, months, years? – DarcyThomas Jul 28 '16 at 11:59
• Could be months. Go and check it yourself, after all. Chemistry is an experimental science. – Ivan Neretin Jul 28 '16 at 13:26

The best info I could come up with is from wikipedia (with no citations for the relevant sections)

https://en.wikipedia.org/wiki/Fischer–Speier_esterification

For reaction with an excess of one reactant and an acid catalysts, it says:

"Typical reaction times vary from 1–10 hours at temperatures of 60-110 °C."

Later it talks about ester reactions in wine:

"Of course, when compared to sulfuric acid conditions, the acid conditions in a wine are mild, so yield is low (often in tenths or hundredths of a percentage point by volume) and take years for ester to accumulate."

Which is a bit of an Apple to Oranges comparison, and is not whiskey, but it gives an indication of 'Yes, slowwwwww'. Or something like that.