Molecular Manipulations
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Theoretical question, ether bond polymer
This may be a dumb question.
Ether bonds can form when two alcohols combine, (with an acid catalyst generally) producing water and an ether: R-O[H + HO]-R → R-O-R +
H2O.
Now suppose you have a polyhydroxy alcohol, with a hydroxy group on each end of the molecule. What would keep them from forming a high molecular
weight polymer? nHO-RO[H + HO]-RO[H + HO]-ROH → nHO-R-O-R-O-[...]ROH + 2n H2O.
Has this been done before and I've just never heard of it? It seems so simple that if it works I should have heard of it.
[Edited on 17-2-2015 by Molecular Manipulations]
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Crowfjord
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Ethers will not form from alcohols without heat and a catalyst, like a strong acid.
Polyethylene glycol is an example, a poly-ether of ethylene glycol. There is also diethylene glycol, etcetera. I'm sure there are many others.
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Chemosynthesis
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Additionally, factors such as the temperature of reaction and, for a vapor phase reaction, flow rate (time in contact with a catalyst) helps determine
the proportion of products. In extreme cases, it may be possible to distill out products of lower molecular mass before further reaction to avoid
continued polymerization. In practice, you will likely get byproducts, such as ethylene glycol, diethylene glycol, and triethylene glycol in their
respective syntheses.
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UC235
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Quote: Originally posted by Chemosynthesis  | | Additionally, factors such as the temperature of reaction and, for a vapor phase reaction, flow rate (time in contact with a catalyst) helps determine
the proportion of products. In extreme cases, it may be possible to distill out products of lower molecular mass before further reaction to avoid
continued polymerization. In practice, you will likely get byproducts, such as ethylene glycol, diethylene glycol, and triethylene glycol in their
respective syntheses. |
For example, treating ethylene glycol with sulfuric acid and distilling gives almost all 1,4-dioxane with a small amount of dark-colored polymeric
goop. Dioxane boils lower than any other possible product (except if it rearranges to acetaldehyde, which doesn't seem to happen).
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Molecular Manipulations
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Thanks for your replies everyone, especially UC235, I want to make some 1,4-dioxane now.
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We are all here on earth to help others; what on earth the others are here for I don't know. -W. H. Auden
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Metacelsus
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Formaldehyde also polymerizes to paraformaldehyde, which has ether linkages.
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