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Making Esters

  1. Sep 26, 2016 #1
    1. The problem statement, all variables and given/known data
    I had a lab where we had to create esters. One of the discussion questions are
    What must be done before the esters are used as you suggest in (e)?

    2. Relevant equations


    3. The attempt at a solution
    I suggested esters are used for perfumes, cosmetics, household cleaners, and scented candles. However, I am unsure of what needs to be done. Is this question asking if the ester has to undergo another reaction in order to be safe?
     
  2. jcsd
  3. Sep 26, 2016 #2

    Borek

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    Hard to help without knowing the context. Can you elaborate a bit on what you did during the lab?
     
  4. Sep 26, 2016 #3
    I took ethanoic acid and mixed it with various alcohols; meth, prop, pent to produce esters that smell like fruit.
     
  5. Sep 26, 2016 #4

    epenguin

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    That it smells like fruit doesn't tell you that what you have in your flask is an ester, it tells you that it contans an ester. :oldwink:
     
  6. Sep 26, 2016 #5
    Don't you have to remove water from the ester in order to be able to use it, as in condensation reaction.
     
  7. Sep 27, 2016 #6

    Borek

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    Another hint: not only water.

    What you have prepared was a mixture of acid/alcohol/ester/everything. You need the ester, right?
     
  8. Sep 27, 2016 #7
    Im confused when you react acid and alcohol dont you have just an ester?
     
  9. Sep 27, 2016 #8

    epenguin

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    You said yourself you produce water in the esterification reaction. Even if you have none there or anything else to start with which is not the case. And see Borek's answer. And do all chemical reactions go to 100% product and nothing else?

    You have really made some ester, which makes you better off than one poor student who was being made to learn the smells of the different esters from a book or list!!

    The question is asking you some sense of reality or laboratory reality beyond just diagrams of carbon, hydrogen and oxygen atoms rearranging.

    The site does not give students the answers to homework questions, but helps them get it themselves. You should read something about the practice of organic chemistry in your book and at least have some ideas you could briefly state here. I don't think anybody could be expected to predict everything you have to do to get pure industrial type ethyl acetate like you can buy another bottle for solvents or so on, but if you make a little effort to we could come back with more.
     
  10. Sep 27, 2016 #9
    Woah I simply did not know what this question was asking.

    I think i have the answer now...
     
  11. Sep 28, 2016 #10

    epenguin

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    That's not yet a very good answer. :oldsmile:

    ∨∨∨∨
     
  12. Sep 29, 2016 #11

    Dr Uma Sharma

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    Esters have very high tendency to react with water and go for the reverse reaction ...so when preparing esters you must have some method to keep removing water so that you can get more ester as product.
     
  13. Sep 29, 2016 #12
    Sorry, my answers was to remove the catalyst because sulfuric acid was added. I also wrote that it has to be able to evaporate in order to be able to smell it. Next I put that it has to be made so that it doesn't react with water, so it does not form back into an acid, essentially it has to be safe for the use of humans.
     
  14. Sep 29, 2016 #13

    Borek

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    Sadly, you are still not there. We were trying to tell you you need to purify your product. Acid removal is a part of that process, but it is easier to separate the ester than to remove every impurity separately. Distillation comes to mind (although it is the only viable way of dealing with the problem).
     
  15. Sep 29, 2016 #14
    Okay I see, thank you very much.
     
  16. Sep 30, 2016 #15

    epenguin

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    0K the question is just trying to probe or stimulate you for any appreciation of laboratory chemistry that is beyond just the schematic pictures of atoms in molecules rearranging. And you showed that this is necessary. We are talking about this as a spectator sport for the moment, But I hope that you will have a laboratory course later.*

    Before that, it would be advisable to read up whatever you have in your textbook about the technique of organic chemistry, and also look at some videos on it, for example

    which explains and illustrates reflux and distillation, both involved in the classical methods for preparation of an ester. Another reality that you will see you in the following that may have escaped is the phase separation any substantial amount of the ester and anything aqueous.

    What you have in a bottle of ethyl acetate that you can buy for use as e.g. solvent, Is pure ethyl acetate. What you have instead in a reagent flask what test tube like the one you did is a mixture of all the reagents and the product (and possibly byproducts). To get the first from the second is purification.

    You can find any number of videos on this reaction and purification online (YouTube). Here are some links, and they will lead you to any number of others. The third one below perhaps is best for the rationale. You will notice that they are all a little different. A notable difference is that it sounds like a good idea, as you said, to neutralise the acid after the reaction, and in most of the videos this is done with sodium carbonate or bicarbonate. In the third, he doesn't and claims that it is not necessary. It just goes to show that as Jacob Bronowski says in his book ‘The Ascent of Man’ Science is not as students get the impression a series of rigid rules for example of the handling of test tubes, but there are no rules even about the handling of test tubes that the inspired scientist that does not consciously break for some reason.

    Follow the videos and particularly their rationale, and you will see there is quite a lot more to it than you thought of, but they may help you feel less of a fool when you have to do this in the laboratory. :oldsmile: (Includes things like knowing about things like boiling stones or which way you flow the water in the condenser). Especially as for organisational reasons quite often the laboratory practice tends to be rather uncoordinated with the theory lessons.



    https://hobbychemistry.wordpress.com/2015/04/17/synthesis-of-ethyl-acetate/

    https://hobbychemistry.wordpress.com/2015/04/17/synthesis-of-ethyl-acetate/://www.docbrown.info/page04/OilProducts10b.htm [Broken]



    Other esters
    http://cosmolearning.org


    *(My hobbyhorse message: some laboratory chemistry is essential to scientific and general education because most of chemistry is only seen, and only happens in the laboratory. Though not advisable, you could just about get away without it in physics in that most physics has every day exemplifications that you can see around: forces, gravitation, friction, surface tension, optics of reflection and refraction and light generally, a long list including even electricity and magnetism - though here I point out that you wouldn't see very much electricity and magnetism without chemistry and, because you wouldn't have copper and iron.)
     
    Last edited by a moderator: May 8, 2017
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