NuovoChem
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Boric Acid Catalysis of Amide
I have seen much encouraging research into the formation of amides from carboxylic acid and amines. Still, most of the work seems to have been
conducted using benzylamine and 4-phenylbutyric acid as models in the studies (I guess we all have been reading the same books). There does not seem
to be a lot of work on any of the catalyzed reactions in any solvent system other than toluene or xylene. As these solvents are highly non-polar, I
would like to know if any organic or natural solvent may be used (I suppose these solvents were used due to the lack of hydrogen bonding between
solvent molecules, as far as I can deduce). There has been little discussion on induced dipole interactions present in other solvents (like
natural/vegetable oils and fatty acids derived from natural oils). Does anyone know of any scenario whereby gaseous amines (MMA, DMA) or ammonia have
been used with fatty acids or vegetable oils (triglycerides) to produce amides? I would be very much interested to know what all have to say.
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bananaman
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Amine + Carboxylic acid --> Amide + Water
Xylene/toluene/benzene are able to form azeotropes with water. Removing the water aids in promoting the reaction.
By other natural/organic solvent, are you refering to alcohols? (Alcohols + carboxylic acid --> Esters + Water) A competing reaction.
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ScienceSquirrel
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Amines are a lot more nucleophilic than alcohols and amides are the preferred product if you mix an ester with an amine.
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NuovoChem
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By natural/organic solvent, I am actually referring to the carboxylic acid. The carboxylic acid, in this case a naturally occurring aliphatic
carboxylic acid, is an oily liquid. The amine is secondary, a gas. Currently, thermal condensation to promote amide bond formation is requiring high
temp, and, (because the amine is gaseous at ambient conditions) high pressure. If boric acid were to work in this case, that would be a magic bullet.
Still, I see no reference to the boric acid catalysis other than when used with toluene, xylene, or some solvent much like the two. Can this system
be applied to any non-polar system so long as the water is accurately removed (like by molecular sieves). Does anyone know? Can anyone postulate?
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Nicodem
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Thread Moved
19-3-2013 at 12:00 |
bananaman
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I am not too sure about the catalysis by boric acid, though there is a journal article about the reaction between boric acid and amine.
Inorg. Chem. 1964, 3(8), 1144-1147
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Nicodem
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Quote: Originally posted by NuovoChem  | | Currently, thermal condensation to promote amide bond formation is requiring high temp, and, (because the amine is gaseous at ambient conditions) high
pressure. If boric acid were to work in this case, that would be a magic bullet. |
You need to search the literature to find the literature:
Russian Journal of Applied Chemistry, 2009, 82, 613−617 and the references 1, 2 and 3 therein.
Normal pressure of ammonia, high temperatures and solvents other than toluene/xylene. Almost what you wanted.
| Quote: | | Can this system be applied to any non-polar system so long as the water is accurately removed (like by molecular sieves). Does anyone know? Can
anyone postulate? |
The current understanding of the catalysis mechanism does not appear to allow for the use of strong H-bond donating solvents (lower alcohols, etc.).
At the same time, due to the obvious reasons, the solvent must not dissolve any relevant amount of water when this is being removed azeotropicaly and
its boiling point should be near the optimal reaction temperature. This effectively reduces the useful solvents to toluene and xylene. I can't see any
reason why anyone would want to use anything else except maybe due to solubility issues, but this could be solved by using a nonvolatile polar
cosolvent.
Molecular sieves generally do not remove water effectively at the required reaction temperatures.
There are other catalysts that can promote the direct amidation, some can do this with ammonia and volatile amines. Check the literature.
PS: Please open threads without references only in the Beginnings section. This is of your own interest, because threads without references often lead
nowhere. See the forum guidelines for more information.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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maxpayne
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CHARVILLE, HAYLEY (2012)
Direct Amide Formation Between Carboxylic Acids and Amines: Mechanism and Development of Novel Catalytic Solutions
Durham theses, Durham University. Available at Durham E-Theses
Direct Amide Formation Between Carboxylic Acids and Amines: Mechanism and Development of Novel Catalytic Solutions
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