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Author Topic: C2O4  (Read 4769 times)

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caters

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C2O4
« on: July 27, 2014, 08:40:22 AM »

Here is 1 possible dot structure of C2O4:

CO2-O-C=O

CO2 group:

[O-C=O  :resonance: O=C-O]

And here are some others:

[CO2-CO2]2-

CO2 group:
O-C-O
       

O-O-CO-CO(in a ring. CO is the carbonyl)

OC-O-CO-O(again, in a ring)

Why is it that on this page here of C2O4:
http://en.wikipedia.org/wiki/C2O4

that CO2-O-C=O which was my first dot structure isn't included when it also follows the molecular formula? All the formal charge there is is that 1 carbocation and 1 oxyanion. I would guess that it is because a carbocation and an oxyanion would want to react and they would want to form a carbonyl. But then again that oxyanion is in a resonance structure so the negative charge is spread across the 2 O's just like it is in NO2.



and what would that compound represented by my first dot structure be called?

Possible Intramolecular reaction:

CO2-O-C=O  :rarrow: C-O-C-O(in a ring) with 2 carbonyls.

This is the same thing as the 4th possible dot structure I drew.



« Last Edit: July 27, 2014, 08:56:31 AM by caters »
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Corribus

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Re: C2O4
« Reply #1 on: July 27, 2014, 09:09:12 AM »

Any molecule with this formula would likely have an enormous entropic driving force for formation of two molecules of carbon dioxide. Therefore it's unlikely that any isomer would persist long - if at all - are room temperature long enough to be observed. It seems that even at very low temperature, quasistable isomers are rare. It's not surprising there aren't entries for your proposed structures, which may not have even been studied theoretically. Though you'd have to do a real literature search to be sure.
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Arkcon

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Re: C2O4
« Reply #2 on: July 27, 2014, 09:19:47 AM »

Or like the Wikipedia article explained, freeze some and subject the crystal to x-ray diffraction.  If the x-rays aren't deflected by electron clouds surrounding atoms where you say they are ... then the atoms can't adopt that conformation.  That's not to say they might not adopt that conformation in solution.  But then, you'd have to design a reaction that would only be possible with your conformation, and catch such a product.  Instead of asking Why not?, instead you should ask What if?  You've already done this, realizing a carbocation and oxanion aren't going to sit nicely side by side.
« Last Edit: September 06, 2014, 02:48:02 AM by Arkcon »
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caters

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Re: Carbon oxides
« Reply #3 on: July 28, 2014, 10:34:01 AM »

If C2O4 is very unstable no matter the configuration(that is the structure based on the bonds) and especially unstable in the form that has an oxyanion and a carbocation than how come other carbon oxides are much more stable despite the charges like CO for instance.

There are 2 possible structures with octets for this. They are

1) C=O with the carbon having 1 lone pair and the oxygen having 2 lone pairs.

2) C≡O with C having 1 lone pair and O having 1 lone pair making the oxygen positive and the carbon negative.

This one is an important but very unstable structure.

Why is it so unstable? It is because while carbon isn't so determining as to what charge it prefers, Oxygen is and it really hates being positive because it wants to be either neutral or negative since it is more electronegative than everything else except fluorine. This is why H3O+ isn't really H3O+ but rather an ion in a complex of ions is because of how oxygen hates being positive.

So why are other carbon oxides more stable than C2O4?

and would adding hydrogens to a carbon oxide make the carbon oxide even more stable? Is this how come glucose is so stable and   6 COs bonded together would be extremely unstable just like C2O4 is?

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Corribus

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Re: C2O4
« Reply #4 on: July 28, 2014, 10:43:34 AM »

These questions are so vague and general that it's hard to know what you really are trying to understand. Could you try being more specific?
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caters

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Re: Carbon Oxides
« Reply #5 on: July 28, 2014, 11:21:39 AM »

If C2O4 is very unstable no matter the configuration(that is the structure based on the bonds) and especially unstable in the form that has an oxyanion and a carbocation than how come other carbon oxides are much more stable despite the charges like CO for instance.

There are 2 possible structures with octets for this. They are

1) C=O with the carbon having 1 lone pair and the oxygen having 2 lone pairs. No charges here.

2) C≡O with C having 1 lone pair and O having 1 lone pair making the oxygen positive and the carbon negative.

This one is an important but very unstable structure.

Why is it so unstable? It is because while carbon isn't so determining as to what charge it prefers, Oxygen is and it really hates being positive because it wants to be either neutral or negative since it is more electronegative than everything else except fluorine. This is why H3O+ isn't really H3O+ but rather an ion in a complex of ions is because of how oxygen hates being positive.

So why are other carbon oxides more stable than C2O4 when they too have very unstable structures like CO2 having as a resonance structure a single bond to 1 oxygen making it negative, a triple bond to the other making it positive, and the carbon staying neutral? And if every carbon oxide is either unstable no matter the structure or has unstable resonance structures than why do carbon oxides with just carbon and oxygen exist?

And would adding hydrogens to a carbon oxide make the carbon oxide even more stable? By this I mean that with the fact that carbon oxides tend to be unstable and hydrocarbons tend to be stable would a carbon oxide with hydrogens added to it be less stable than a hydrocarbon but more stable than a carbon oxide?

Is this how come glucose is so stable and 6 COs bonded together would be extremely unstable just like C2O4 is?
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kriggy

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Re: C2O4
« Reply #6 on: July 28, 2014, 08:56:29 PM »

The two structures you wrote for CO are identical, they are resonance structures for CO. There is the third one too:
-C-O+
Neither of them is right and all has flaws:
-C-O+ explains why CO bonds always by carbon in carbonyl complexes, but doesnt explain the bond order (≈2,5) and positive charge on oxygen is unlikely because of high electronegativity
+C≡O- fits with higher electronegativity of oxygen and bond order but there is no positive charge on carbon and doesnt explain why CO bonds by carbon in cabonyls
C=O explains bond order but has issues with electronegativity

Remember that resonance structruers are just representation of borderline state. The true state of the molecule is somewhere in between them.

caters

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Re: C2O4
« Reply #7 on: July 28, 2014, 11:59:25 PM »

the one with the single bond though does not have octets. However the one with the double bond and the one with the triple bond do and thus are more likely despite the charges
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caters

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Re: C2O4
« Reply #8 on: July 30, 2014, 12:01:16 PM »

and it has been experimentally found that the positive charge in CO is on oxygen because 3 bonds + 1 lone pair = 5 electrons and oxygen normally has 6.
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