Thomas Winwood
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Hypothetical musings - single molecule polyester, ethene and oxidising agents
In regular polyesters there are two molecules involved - a diol and a dicarboxylic acid (or more usually the acid chloride due to added reactivity and
the gaseous nature of the HCl byproduct). It would seem nice to me if it were possible to produce a single molecule which does both jobs, with a
carboxylic acid group at one end and a hydroxyl group on the other. It can then polymerise with itself. I plan to look at the synthesis of a suitable
molecule.
My problem came when I realised that I needed some way of shielding one of the two alcohol groups while I prepared the carboxylic acid end. Grignard
reagents with methanal seemed promising but I ran into a similar problem of brominating the alcohol after using the Grignard.
My idea is to start with propenol, oxidise the alcohol group to a carboxylic acid and then hydrate the double bond. This has the unfortunate result of
a secondary alcohol rather than a primary, but my other idea of using a bromine atom rather than the double bond did not work because I realised the
hydroxide ions would more readily react with the dissociated hydroxonium ions and form the salt of the carboxylic acid rather than substitute to the
bromine. In any case this should not be an issue, because Paul Wang's thesis leads me to believe there is minimal disadvantage to an ester made with a secondary alcohol rather than a primary,
especially as a proof-of-concept.
Regardless, my question is: what should I look out for with regard to the double bond in the presence of oxidising agents? I figured a stronger
oxidising agent like KMnO<sub>4</sub> would oxidise to form an epoxy compound, but I don't know this for certain - my sources give
conditions for formation of epoxyethane as 250-300°C and 15atm in the presence of oxygen gas. Obviously I'm not going to be using those sorts of
pressures!
Any other relevant information will be accepted.
[Edited on 25/11/2005 by Thomas Winwood]
I\'ve been told having a sig is banned, despite the facility being available. Um...contradiction?
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DeAdFX
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How about glycolic(sp) acid. Check out the msds here http://www.jtbaker.com/msds/englishhtml/g6821.htm and where you can get ithttp://www.chemistrystore.com/glycolic_acid.htm
edit: not exactly what you were looking for but I thought I would share this patent. It talks about dihydroxyl polycarbonates. I skimmed over it but
anyways http://www.freepatentsonline.com/6884864.html Might want to check some patents to while your at it
[Edited on 26-11-2005 by DeAdFX]
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sparkgap
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Lactic acid, glycolic acid (like DeAdFX said), and other alpha-hydroxy acids have already been put to use in industry as biodegradable polymers.
Nature also makes use of these in strengthening the cell walls of some organisms (polyhydroxybutyrate, IIRC).
Permanganate would either turn your double bond to a diol or cleave it to two carbonyls, so you can scratch that route if you want AHAs.
If bromine and red P isn't a problem for you (which I'm not sure in your case), Hell-Volhard-Zelinsky is a nice step.
sparky (~_~)
P.S. Oh, and if you're planning to carry out something similar for polyamides, nylon-6 is supposed to ring a bell for you...
"What's UTFSE? I keep hearing about it, but I can't be arsed to search for the answer..."
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Thomas Winwood
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Yes, what I was looking at was longer-chain analogues of glycolic acid. Apparently polyhydroxyalkanoates see quite a lot of use in tissue engineering
and surgical equipment since they're biodegradable.
BromicAcid suggested to start with a cyclic ether, cleave the ring with a strong haloacid, oxidise the alcohol, substitute the bromine for an alcohol
group using NaOH, then react with dilute acid to regain the acid from the sodium salt. It's a nice idea.
I\'ve been told having a sig is banned, despite the facility being available. Um...contradiction?
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liwenbinyk
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Hallo all.
Now I study on Polylactide materials. What can I settle the water problem during process of PLA . There is not schlenk line and glovebox.
thank you for anyone help!
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