Sciencemadness Discussion Board

iron/glycerol compound

guy - 11-8-2006 at 14:38

Fe2O3, NaOH, and glycerol were added into a crucible and heated in an open flame. The mixture started to boil with lots of smoke evolving. Then water was added to the mixture was cooled down and filtered. What wa left was a clear(as in no particles) dark, red-brown solution. This compound is stable even when highly diluted (giving a golden-brown solution).

Other notes: I tried just Fe2O3/glycerol and it didn't work.

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I just found out that glycerol decomposes to the toxic Acrolein. I accidently breathed some of the smoke, will I die?

[Edited on 8/11/2006 by guy]

not_important - 11-8-2006 at 22:34

Not from a trace : http://www.atsdr.cdc.gov/tfacts124.html


as for the less pressing issue of the complex, you may be getting some air oxidation of the glycerol with the base there.

Nicodem - 11-8-2006 at 23:13

The conditions were extreme enough and oxygen was present so to allow traces of sodium ferrate (IV) or (VI) to have formed (Na2FeO3 and Na4FeO5). I don't know what's the color of ferrate salts, but I could guess they are red. However I would have imagined the ferrates are strong enough oxidants to oxidize glycerol. Perhaps glycerol actually did get oxidized to some acids which on turn dissolved some Fe2O3 forming a red solution.
Anyway, your experiment does not demonstrate the formation of a complex.

PS: You are more likely to get cancer from acrolein in fried potatoes in your favorite fast food by chronic exposure than a one time acute exposure in such an experiment. Anyway, acrolein has a sharp odor to warn you about its presence.

guy - 11-8-2006 at 23:26

Quote:
Originally posted by Nicodem

Anyway, your experiment does not demonstrate the formation of a complex.



So do you think it is regular Fe3+? Adding NaOH to it causes NO precipitate. Ferrate(VI) ions will decompose rapidily if not in high pH.

not_important - 11-8-2006 at 23:59

guy, check these

http://www.freepatentsonline.com/7034172.html

http://www.deas.harvard.edu/environmental-chemistry/publicat...

chemoleo - 12-8-2006 at 00:12

No way it's going to be ferrate. Read the thread on it. It's violet, highly unstable, and would undoubtedly oxidise any of the glycerol. Even BaFeO4, which is insoluble, isn't exactly stable.

Quote:
So do you think it is regular Fe3+? Adding NaOH to it causes NO precipitate. Ferrate(VI) ions will decompose rapidily if not in high pH.

Guy, this means nothing, as your solution is already highly basic anyway. Check the pH first, then neutralise.

Did you weigh things? Or just chuck it together randomly?

Nicodem - 12-8-2006 at 01:14

Yes, I stand corrected. Indeed, there is no way any ferrate could form in such a reductive ambient when the oxidative potential of ferrates is considered.

Guy, try the same thing with NaOH/glycerol only. I bet the solution will become brown-red.
Solutions of NaOH in EtOH become red if left standing exposed to air in a couple of days at room temperature (the color indeed reminds of some Fe(III) salts or oxide). I always thought it was because the ethoxide ions would be easily oxidized by oxygen forming compounds that would self condense in basic conditions to some brown-red, indefinable crap. Some brown tar actually begins to precipitate if left standing several days. I would assume something similar would happen to glycerol as well, especially if the oxidation is catalyzed by the presence of Fe(III) and speeded by heat.

not_important - 12-8-2006 at 06:25

Guy's results may be related to the Guerbert reaction, part of a set of reactions taking place at elevated temperatures in the prescence of strong base. These give branched alcohols built up from simplier alcohols, and carboxylic acids from those alcohols

http://www.zenitech.com/documents/guerbet_chemistry.pdf

Coming into play with compounds that can give unstatured carboxylic acids, although generally at a bit higher temperature, is the Varrentrapp and related reactions, which sometimes affect saturated acids as well.

Nicodem's example may be related to the oxidation shown in the Guerbet PGF, oxidation of alcohols in the presence of strong base shows up in other cases.

edit - use the correct names of people, duh.


[Edited on 12-8-2006 by not_important]

guy - 12-8-2006 at 17:14

Quote:
Originally posted by Nicodem
Yes, I stand corrected. Indeed, there is no way any ferrate could form in such a reductive ambient when the oxidative potential of ferrates is considered.

Guy, try the same thing with NaOH/glycerol only. I bet the solution will become brown-red.
Solutions of NaOH in EtOH become red if left standing exposed to air in a couple of days at room temperature (the color indeed reminds of some Fe(III) salts or oxide). I always thought it was because the ethoxide ions would be easily oxidized by oxygen forming compounds that would self condense in basic conditions to some brown-red, indefinable crap. Some brown tar actually begins to precipitate if left standing several days. I would assume something similar would happen to glycerol as well, especially if the oxidation is catalyzed by the presence of Fe(III) and speeded by heat.


I tried NaOH and glycerol only and nothing happened. Was your color very dark?

And how can ethanol and NaOH becomoe colored? Was your's pure ethanol?

not_important - 12-8-2006 at 20:29

Alcohols can be oxidised, even by air, when hydroxide is present, aldehydes or ketones and acids can be formed. Aldehydes and base go to condensation products, get enough carbonyls and double bonds and you have colour.

guy - 12-8-2006 at 23:05

Quote:
Originally posted by not_important
Alcohols can be oxidised, even by air, when hydroxide is present, aldehydes or ketones and acids can be formed. Aldehydes and base go to condensation products, get enough carbonyls and double bonds and you have colour.


Oh that's interesting. What would the mechanism be? The formation of an alkoxide, then oxidation of the alkoxide by oxygen? 2RCH2O- + O2 ---> 2RCHO + 2OH-

And if you happen to have any sources on that it would be cool.

JohnWW - 13-8-2006 at 02:19

Ferrate (VI) can be made by oxidation of alkaline Na or K ferrite (III) by Cl2 gas, hypochlorite, or reagents like plumbate or bismuthate, or electrolytically. The color of ferrate (VI) salts is magenta; resembling permanganate, but somewhat more reddish, due to the intense charge-transfer absorption band in the visible part of the spectrum.
If perferrate (VII) could be made (and it probably could be, by electrolysis of cold alkaline ferrate solution at sufficiently high voltage), the charge-transfer band would be shifted to a still longer wavelength and be even more intense, and it would probably be an intense bluish-purple color (bluer than permanganate).

not_important - 13-8-2006 at 09:47

Sorry, guy, no good references. Almost everything that gives any detail relates to fusion or at least elevated temperatures with strong aqueous solutions; the more room temperature ones have all been of the "this reaction happens" mention. I suspect that it is slow enough and leads to such a mess of products that it's attracted little attention, showing up only in such publications as the Wallachian Journal of Natural Philosophy or Annals of the Technical Arts in Ragusa.

The Guerbert pdf has a reference or two for caustic fusion oxidations.