Equilibrium law
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I'm doing an investigation on the reaction:
Ethanoic acid + ethanol -> ethyl ethanoate + water
I have to investigate into any aspect of this equation but I have no idea what to do. I can't find any information on it anywhere. I don't know whether it needs a catalyst or what temperature I can expect the best results.
I thought I could investigate into the results at different temperatures but I don't know how I would go about this and I'm supposed to get in a list of apparatus and chemicals before the end of next week. I don't want anybody to do the work for me, I just would like a bit of help please!
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Ulex replies
In a way, you give me plenty of scope and yet this particular reaction has its limitations.
I suppose the first thing is to get it to work. Ethanoic acid and ethanol do not react to any significant extent at room temperature because the reaction (a) reaches equilibrium and (b) does so very slowly indeed.
To overcome the rate problem you need to reflux and to provide a catalyst. To make the reaction go to something like completion you need to prevent the water formed from doing the reverse reaction. The usual way of combining these functions is to add a little concentrated sulphuric acid which both catalyses the reaction and holds on to water.
What I have just described, translated into a detailed procedure, is a standard laboratory preparation of ethyl ethanoate which you should find described in any textbook of preparative organic chemistry. There are several ways of doing the preparation including one rather clever one which involves dripping ethanol into a boiling mixture of ethanoic acid and sulphuric acid and distilling off the ester as it is formed. Don't attempt to write your own instructions here - it would not be safe to do so and is competely unnecessary, many writers have been here before you.
Now, what else could you do? The obvious thing is to find the equilibrium constant at a given temperature using dilute sulphuric acid as the catalyst. The snag is that at ordinary temperatures the mixture takes weeks to reach equilibrium! Also the arithmetic needed to work out the answer is quite tricky.
You could try different alcohols to see if the preparation can be adapted to other esters.
Good luck!
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updated: 23 September 2008
