Making esters
Paul St.Louis
I have attempted to make simple aromatic esters by refluxing carboxylic
acids with alcohols in the presence of a few drops of sulfuric acid and
have not had much success getting a lot of product ( faint smells only).
I am using a variety of low carbon # acids/alcohols and refluxing for
20-30 minutes.
Can anyone advise ??
Paul St.Louis
Fellowes HS
Pembroke ON Canada
Alan "Uncle Al" Schwartz
Esterification is an equilibrium process. Either add a large (fivefold
or more) excess of your alcohol (which can be stripped) or your acid
(which can be extracted into aqueous base), or provide for physical or
chemical water removal.
--
Alan "Uncle Al" Schwartz
Uncl...@ix.netcom.com ("zero" before @)
http://www.netprophet.co.nz/uncleal/
(Toxic URL! Hazardous to children, Liberals, and most mammals.)
"Quis custodiet ipsos custodes?" The Net!
K Fowler
Paul St.Louis wrote:
>
> I have attempted to make simple aromatic esters by refluxing carboxylic
> acids with alcohols in the presence of a few drops of sulfuric acid and
> have not had much success getting a lot of product ( faint smells only).
> I am using a variety of low carbon # acids/alcohols and refluxing for
> 20-30 minutes.
> Can anyone advise ??
>
> Paul St.Louis
> Fellowes HS
> Pembroke ON Canada
A classic procedure (See Fieser and Fieser Vol.1 p 678):
1 mole acid + 3 moles MeOH + sulfuric acid (15 mL for aromatic acids, 3
mL for aliphatic) + 300 mL ethylene dichloride or methylene chloride.
Reflux gently overnight.
The water generated by the esterification is immiscible with the
chlorinated solvent and will float on top, thus driving the reaction
toward completion. It's worked nicely for me on many occasions.
KWF
Paul A. Deck
K Fowler <kfo...@icos.com> wrote:
>KWF
I would like to point out that ethylene dichloride is on the EPA's
carcinogen list [Merck Index], so the use of that solvent is probably
a bad idea in a high school classroom experiment. Sure it can be done
safely, but eventually you'll get sued.
Ain't nuthin' easy.
Paul
Paul A. Deck
Assistant Professor of Chemistry
Virginia Polytechnic Institute and State University
Laboratory
In <4ogif3$s...@nntp.igs.net> "Paul St.Louis" <stl...@renc.igs.net>
writes:
>I have attempted to make simple aromatic esters by refluxing
carboxylic
>acids with alcohols in the presence of a few drops of sulfuric acid
and
>have not had much success getting a lot of product ( faint smells
only).
>I am using a variety of low carbon # acids/alcohols and refluxing for
>20-30 minutes.
>Can anyone advise ??
>
>Paul St.Louis
>Fellowes HS
>Pembroke ON Canada
>
>
removed to keep shifting the equilibrium towards the product. You need
to add a fractionating column to the top of your reaction flasks to do
this properly.
Since I do not know what type of equipment you have available, that
is as far as I can advise you.
Have fun.
Romas Cesas
Jeremy M. Travins
>Water is formed during the esterification reaction and must be
>removed to keep shifting the equilibrium towards the product.
>You need to add a fractionating column to the top of your
>reaction flasks to do this properly.
No, you don't use a fractionating columns...
You use a "water trap" or as it's commonly called, a Dean-Stark
apparatus. Look for a picture in a laboratory textbook.
Benzene or Toluene is commonly used as a solvent, which then is
refluxed. The water made in the reaction distills out with the
solvent, and then separates from the solvent. The solvent then
is returned to the distilling flask.
There are so many books and research publications
that deal with making esters. You should look up the reaction
which you want to do - chances are, it's been done previously...
Jeremy
Terence Tak-Shing Tam
Hey! We are doing almost the same experiment...
First of all, the reaction is SLOW. Expect about a week for
results. Meanwhile you can monitor the amount of acid remaining by
titration. That will give you an idea whether equilabrium is reached.
Secondly the ester's smell might be covered up by the strong smell
of the acid. You will need to separate out the ester. One way of doing
so might be to add water to extract the alcohol and acid and then extract
out the insoluable ester. Look up their solubility, bp and mp in the CRC
and propose a separation method.
Have fun...
Terence
Allen Adler
On an old episode of The Untouchables, a chemist was sitting in
a restaurant, amusing himself by mixing vinegar and liquor and
producing an ester. I was never able to do it myself, but that
might be partly because I don't remember all the details of what
he said and did. On the other hand, it might be because this was
fiction and you can't really do what he said he was doing. The
acid test was when an attractive woman joined him and, when she
sniffed the concoction, thought it was perfume.
Allan Adler
ad...@pulsar.cs.wku.edu
Jeffrey Bodwin
> First of all, the reaction is SLOW. Expect about a week for
> results. Meanwhile you can monitor the amount of acid remaining by
> titration. That will give you an idea whether equilabrium is reached.
If you want to speed up the reaction, jack up the temp, use a big excess
of the cheaper reagent (in my case, ethanol), and remove water (with a
Dean-Stark trap or similar aparatus). And isn't titration a little
involved? Unless you're doing some close study of the reaction rate, TLC
should be sufficient to follow the reaction along.
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Jeffrey Bodwin
> On an old episode of The Untouchables, a chemist was sitting in
> a restaurant, amusing himself by mixing vinegar and liquor and
> producing an ester. I was never able to do it myself, but that
an alcohol and an acid produces water, so the equilibrium is usually
driven by removing water. Vinegar and liquor are both pretty dilute
aqueous solutions, so unless the TV chemist was distilling his starting
materials at the table, I doubt the reaction would work. Too bad you can't
smell your TV shows, eh?