Azeotropic
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Butyl Acrylate/Toluene azeotrope ?
I'm trying to determine if Butyl Acrylate will azeotropically distill with Toluene. None of the azeotrope tables I've found have this combination
present. If someone has access to this information I would be most grateful if you could post the boiling point temperature and the percentage of
acrylate ester present.
Many thanks in advance!
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JohnWW
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Because toluene (an aromatic hydrocarbon) and butyl acrylate (an aliphatic ester) are so chemically dissimilar, it is rather unlikely that they would
form any sort of constant-boiling-point azeotrope, unless their boiling-points are very close together, and unless the positive or negative deviations
from Raoult's Law of partial vapor pressures are so substantial (which is more likely in compounds with chemical affinities) as to result in a
composition having a maximal or minimal boiling-point.
This would be very much unlike distillations of mixtures of C2H5OH or iso-C3H7OH with H2O, having -OH groups in common and boiling-points of the pure
substances separated by only about 20ºC. These form azeotropes with H2O, resulting in final fractionated distillates containing substantial
percentages of water (30% in the case of isopropanol).
P.S. Toluene has a boiling-point of 110.8ºC; but that given for n-butyl acrylate (which is used in the production of paints and inks in which it
undergoes polymerization, having a strong unpleasant odor) conflicts considerably among the different sources, possibly because of its extreme
tendency to polymerize. Another possibility is contamination with other acrylic esters, particularly sec-butyl and tert-butyl. It is variously given
as 101, 147, 145, 127, 138, 145-149, and 80ºC, so who is one to believe? One would expect that those preparations of it closest in boiling-point to
toluene would be the most likely to form an azeotrope with toluene, while other preparations may not.
Some of the sources of data on it are:
http://monographs.iarc.fr/ENG/Monographs/vol71/mono71-14.pdf
http://www.vistachemie.com/Files/TDS/BAJRC01.pdf
http://www.parchem.com/siteimages/attachment/Butyl%20Acrylat...
www.ilo.org/public/english/protection/safework/cis/products/...
http://www.rohmhaas.com/wcm/products/gpsi/pm/monomers/butyl_...
http://chemicalland21.com/industrialchem/functional%20monome...
http://www.alibaba.com/product-gs/257149444/Butyl_Acrylate.h...
http://www.hellochem.com/En/xz/xz11/106266imtug.htm
http://dspace.lib.fcu.edu.tw/bitstream/2377/4282/1/ace010401...
http://www.chemyq.com/En/xz/xz1/6076ytjeu.htm
http://www.itcilo.it/english/actrav/telearn/osh/ic/141322.ht...
http://www.functionalpolymers.basf.com/portal/streamer?fid=2... (PDF)
http://www.orgsyn.org/orgsyn/prep.asp?prep=cv3p0146
Here is a patent on azeotropes of alkyl esters generally, but there seems to be nothing specifically about any formed by toluene and butyl ester:
http://www.patentstorm.us/patents/5834416/description.html
This site has nothing on any azeotropes formed by butyl acrylate: http://ecosse.org/chem_eng/azeotrope_bank.html
While the Wikipedia article http://en.wikipedia.org/wiki/Azeotrope tends to support my surmises, it offers no method of theoretically predicting whether a particular binary
mixture is likely or not to form an azeotrope at some point in its composition range.
[Edited on 5-10-09 by JohnWW]
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smuv
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I disagree with what JohnWW has said, it is not the chemical similarities that create azeotropes, but the differences. Azeotropes occur when a
sufficiently non-ideal solution is being distilled; under these conditions if the solution sufficiently deviates from Raoult's law an azeotrope is
observed.
One easy method to determine how ideal a solution is, is to mix all of the constituents together and observe the enthalpy of mixing (measured by a
change in temperature upon mixing the constituents). For example mix ethanol and water and you will notice a decrease in temperature, indicating that
a solution deviates strongly from an ideal solution; upon mixing para and ortho xylene one would notice almost no temperature change indicating that
for most purposes the solution can be considered ideal (although it wouldn't be completely ideal) and upon mixing EtOAc and DCM the temperature
increases (IIRC) indicating again the creation of a fairly non-ideal solution. Therefore the more similar constituents of a solution are the closer
to zero the enthalpy of mixing will be and therefore the closer the solution will behave to an ideal mixture.
Some practical examples:
Isopropanol and ethanol only have a 3 degree difference in boiling point, however ethanol distills with about 4-5% water and isopropanol comes over
with about 9% water. This can be (back of the envelope) rationalized by isopropanol's extra carbon which makes it more non-polar than ethanol,
creating a less ideal mixture.
Toluene and water form an azeotrope at 85 degrees containing 20% water. Toluene and water are of course immiscible so the mixture can be considered
non-ideal. The molar composition of the azeotrope ends up being approximately (the vapor pressure of the constituent)/760torr. This value is of
course independent of the ratio of toluene and water, for this reason no matter how many times the mixture is distilled an 80/20 toluene to water (by
weight!) distillate will be obtained.
To address the posters question, for sure toluene and butyl acrylate form a fairly non-ideal mixture; there is possibility that they will form an
azeotrope. Though, the compounds have a nearly 30 degree bp difference which may be enough to overcome the deviations from Roult's law. Azeotropes
are difficult to simply predict. If you however substitute benzene or petroleum ether for toluene there is a much lower chance of observing an
azeotrope.
P.S. Another indirect way of observing enthalpy of mixing, is by volume change upon mixing the constituents. For example upon mixing XmL ethanol and
XmL of water, one will notice that the final mixture has a volume less than 2x.
[Edited on 10-4-2009 by smuv]
"Titanium tetrachloride…You sly temptress." --Walter Bishop
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