chemwizard
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Esterification
Can anybody highlight on how i can effectively and efficiently carry out esterification without using a solvent and azeotropic distillation of water?
Is it possible to carry out esterification using only carboxylic acid, alcohol and catalyst?
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not_important
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All depends on what is being esterfied. If there is an azeotrop of water and the acid, alcohol, or ester, you can distill that off to force the
reaction; if it is of the acid or alcohol obviously you'll use an excess of that. For methyl formate the ester is volatile enough that you can
fractionally distill it away from the reaction mix.
Just having an excess of one of the reactants may force the reaction enough for you. In some cases the ester may be a solid and fall out of solution,
or the water formed is not very soluble in the reaction mix and forms a separate layer, again forcing the reaction.
But in general, no for practical cases. You have an equalibrium condition, unless you either remove one (or both) of the products, or use a huge
excess of one of the reactants, you will have a mixture of acid, alcohol, water, ester, and catalyst.
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matei
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chemwizard,
The answer is yes. Usually laboratory-scale esterifications are made by refluxing the acid in an excess of alcohol (which acts as solvent) and in the
presence of the catalyst (e.g. H2SO4 etc.). You should check Vogel's though for the exact procedures.
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not_important
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| Quote: | Originally posted by matei
chemwizard,
The answer is yes. Usually laboratory-scale esterifications are made by refluxing the acid in an excess of alcohol (which acts as solvent) and in the
presence of the catalyst (e.g. H2SO4 etc.). You should check Vogel's though for the exact procedures. |
Unless the acid is the cheap ingredient. Also depends on what is meant by "effectively and efficiently". Sometimes the alcohol, acid, or even both
form an azeotrope with the ester; or boil just a few degrees away. This makes it more difficult to isolate the ester, especially if it has appreciable
water solubility.
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JohnWW
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I have heard of methyl esters of mixed fatty acids being made by reaction with diazomethane, CH2N2, for gas-chromatographic analysis, but it is
dangerous because CH2N2 is both explosive and highly poisonous, somewhat comparable to HN3. This can be done without using an alcohol (which is also
the esterification reagent) as a solvent.
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not_important
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And the reagents typically used to generate diazomethane are toxic/mutagenic/carcinogenic as well. There's special glassware for working with it,
what looks like ground glass joints have smooth polished surfaces as rough surfaces cause decomposition. The reaction is typically run in ether.
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