Rattata2
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Calcium oxide and alcohols/ethers
I know that Calcium oxide, basically being an anhydride reacts with water to form calcium hydroxide according to the formula CaO + H2O -> Ca(OH)2
which of course can be turned to NaOH by reacting with Na2CO3
I am wondering however if calcium oxide would react with dialkyl ethers or alcohols to form the corresponding alkoxides, and if not then why not?
Seems like it would be quite a convenient way to obtain alkoxides if that were the case...CaO + Et2O -> Ca(OEt)2
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12AX7
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Hmm, could very well be. I recall CaCl2 also forms alcoholates, in analogy to the hydrates it's usually used for. The question here essentially
becomes, is it basic enough? In water, it isn't very basic, but under anhydrous conditions, it has something else going for it.
Try it and see!
Edit: whoa whoa whoa, you typed Et2O, not EtOH 
Tim
[Edited on 8-10-2009 by 12AX7]
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Sedit
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But he ment Et2O Tim.
I was under the impression that CaO underwent hydrolysis at a very slow rate in H2O.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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12AX7
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Well, he said ethers, but I don't get why... what the hell do ethers do, they form peroxides and that's about it, isn't it? They're peculiarly
difficult to cleave (actually, I don't know of an ether cleavage reaction off the top of my head, aromatic ethers don't count). The reaction is
actually balanced, which makes it possible, but I don't see that ether opening up. As for alcohol, it would leave an extra H2O, which would go with
another CaO, cutting yield in half and potentially requiring purification.
CaO does react with water exothermically. A sack of fresh CaO dropped into just enough water and stirred around heats the water to boiling as it
forms slaked lime (Ca(OH)2).
Tim
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DJF90
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Hydroiodic and hydrobromic acids are used to cleave ethers, although the latter requires boiling of the reaction mixture. I also seem to recall an
oxidising agent that cleaved methyl ethers (I think), it might have been Fetizon's reagent. Calcium oxide is listed as a drying agent for alcohols so
I dont think it will react appreciably with them. And yes, the reaction water with CaO is fairly fast and exothermic.
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Rattata2
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Yeah perhaps ethers wouldn't be the way to go since they're so stable...perhaps alcohols would react in this way but again I'm not really 100% sure on
that...I think if an alcohol were to work though it would only produce the mono-alkoxide. Which could be alright but means upon conversion to the
sodium salt would yield 50% NaOH and 50% of the alkoxide...
But as you said DJF90, CaO apparently finds use as a drying agent for alcohols so that might not happen either.
Shucks, thought I'd might have found a convenient way to get to those alkoxides!
All well at least this general process can be used to generate hydroxides...thinking about building a setup for calcining CaCO3 to get CaO, so I can
use that to produce decently high-purity NaOH in a recyclable manner.
Tis a shame alkoxides are so hard to get at, they'd be useful if there was a somewhat viable path (ie: not reacting alkali metals with alcohols :p)
edit: When I obtain some CaO I will give this a try just to be sure (with both ethers and alcohols) but I doubt the results will be significant...if
they are I'll post back 
[Edited on 10-8-2009 by Rattata2]
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12AX7
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What about EtCl or EtBr, might that etherate CaO? Hah, something of a Grignard approach there... the result would have to be Cl-Ca-OEt. If that in
turn precipitates CaCl2 then you'd be left with Ca(OEt)2.
If CaO is good for drying those, too, then to hell with any of it. 
Tim
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DJF90
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I think this is probably the wrong way to go about an alternate prep. of alkoxides. Aluminium alkoxides are relatively simple to prepare, and
aluminium is very available. Then perhaps an alcoholic solution of this could be added to an alcoholic solution of NaOH, with Al(OH)3 precipitating? I
dont know if this would work - its pure speculation. But its a possibility until proven otherwise.
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chloric1
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Quote: Originally posted by DJF90  | | I think this is probably the wrong way to go about an alternate prep. of alkoxides. Aluminium alkoxides are relatively simple to prepare, and
aluminium is very available. Then perhaps an alcoholic solution of this could be added to an alcoholic solution of NaOH, with Al(OH)3 precipitating? I
dont know if this would work - its pure speculation. But its a possibility until proven otherwise. |
I think the aluminum alkoxides need mercuric chloride as a catalyst. The mercuric salt removes the oxide film exposing extremely reactive Aluminum to
the alcohol molecules.
Fellow molecular manipulator
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Theophrastus
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| Quote: | [quote=chloric1]
I think the aluminum alkoxides need mercuric chloride as a catalyst. The mercuric salt removes the oxide film exposing extremely reactive Aluminum to
the alcohol molecules.
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I suppose with a little initial heat, you could also use a smidge of iodine. I've done a similar sort of thing, only with a layer of wax as well, to
inscribe some lovely wording into an aluminium plate.
[Edited on 13-8-2009 by Theophrastus]
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DJF90
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Yes it probably requires a catalytic quantity of HgCl2; All preps I have seen so far use the mercury salt to activate the aluminium. I would think if
you "wash" the aluminium with conc. HCl before adding straight into the alcohol them this need of catalyst is bypassed - there should be very little
oxide layer if you're quick about the transfer. Iodine could also be a good activator - I'm fairly certain I've seen its use with mercury chloride
(i.e. used simultaneously) in an aluminium alkoxide prep.
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stoichiometric_steve
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Although this is off topic, i think CaO is not an anhydride.
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unionised
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| Quote: Originally posted by Sedit | But he ment Et2O Tim.
I was under the impression that CaO underwent hydrolysis at a very slow rate in H2O. |
The slaking of quicklime is farily fast and vigorous.
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