thesmug
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Organic Oxidation
I apologize in advance for this extremely beginner question but, earlier today I was learning about oxidation states in organic chemistry and one
example was oxidation of ethanal to acetic acid. I understand how the oxidation works, but where does the oxygen come from? I assume from whatever
caused the oxidation but with things like fluorine which also cause oxidation, if you were to oxidize ethanal with a non-oxygen containing oxidizer
would you get something like (using fluorine as an example again) CH3COF?
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DraconicAcid
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You could get that (or a whole bunch of fluorinated organics). Oxidations are also often done in aqueous solution, so additional oxygen can come from
the water.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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thesmug
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Thank you very much, DraconicAcid
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BromicAcid
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With carbon the term oxidation does not necessarily involve changing the oxidation number, it involves increasing the number of bonds between carbon
and oxygen. Fluorine does not oxidize the carbon in ethanal any more than it is, it starts in the +4 state and ends in the +4 state. Going from
ethane to ethanol to ethanal to acetic acid however is still called an oxidation despite the carbon having the same number of bonds (hybridization
state does change though). At least that is the simple way to look at it.
This is opposed to something like reacting uranium tetrafluoride with fluorine:
UF<sub>4 (s)</sub> + F<sub>2 (g)</sub> ----> UF<sub>6 (g)</sub>
In that case the formal oxidation number of the uranium is going from +4 to +6 due it losing 2 electrons.
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DraconicAcid
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Quote: Originally posted by BromicAcid  | | With carbon the term oxidation does not necessarily involve changing the oxidation number, it involves increasing the number of bonds between carbon
and oxygen. Fluorine does not oxidize the carbon in ethanal any more than it is, it starts in the +4 state and ends in the +4 state. Going from
ethane to ethanol to ethanal to acetic acid however is still called an oxidation despite the carbon having the same number of bonds (hybridization
state does change though). At least that is the simple way to look at it. |
The number of bonds is not the oxidation number. In methane, the carbon is -4 (because hydrogen is always +1 unless bonded to a metal). In carbon
tetrafluoride, the carbon is +4 (because fluorine is always -1).
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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thesmug
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BromicAcid that makes more sense. Here's the video I heard this from:
https://www.khanacademy.org/science/organic-chemistry/organi...
Is what he's saying wrong?
Also, is there a way to selectively oxidize atoms such as oxidizing the 1-position carbon in a molecule but not the 2-position one?
[Edited on 4/6/14 by thesmug]
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BromicAcid
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Mr. DraconicAcid, what you are saying is correct. But as I mentioned in my post, I was simplifying things considerably (even pointing out that I
wasn't accounting for hybridization). Indeed carbon has an array of formal oxidation states that it can pass through but some of them are simply for
book keeping purposes. A more relevant example of what I was trying to say would be the <b>oxidation</b> of carbon tetrachloride to
phosgene. It is not an oxidation in the sense that the oxidation number, formal or otherwise is changed, but simply in the attachment of more oxygen
atoms to the target chemical. These types of reactions are often referred to as oxidation for that reason alone. However with many other elements,
adding an oxygen does result in expansion of valence to add that additional oxygen thus increasing the number of bonds/oxidation number as well.
Looking at that video it seems you are talking about how to determine formal oxidation number however. If you tell me the time that you're talking
about in the video I will check it out.
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blogfast25
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| Quote: Originally posted by DraconicAcid | | You could get that (or a whole bunch of fluorinated organics). Oxidations are also often done in aqueous solution, so additional oxygen can come from
the water. |
I don't know a great deal about this but can water oxidise an aldehyde? I always thought you needed a fairly strong oxidiser for that...
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thesmug
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BromicAcid in the video he talks about the oxidation of ethanal at about 4min.
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DraconicAcid
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| Quote: Originally posted by blogfast25 | | Quote: Originally posted by DraconicAcid | | You could get that (or a whole bunch of fluorinated organics). Oxidations are also often done in aqueous solution, so additional oxygen can come from
the water. |
I don't know a great deal about this but can water oxidise an aldehyde? I always thought you needed a fairly strong oxidiser for that...
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No. But if you were to oxidize an aldehyde with silver ions or chlorine in aqueous solution, the oxygen would come from the water, even though it's
not the oxidizing agent.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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