Impossibly Covalent Molecule. Why?

[Juggernauts]

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Why is this molecule impossibly covalent?

 

[Juggernauts]

never mind. just noticed the reason.

 

[yappy]

What was the reason why it is an "impossible covalent" molecule.

 

[Juggernauts]

Too many bonds on the oxygen.

The oxygen has two bonds to the carbon and one bond to a hydrogen. This gives oxygen a +1 charge. The way it sits right now, the oxygen is a kind of a mix between carbonyl and a hydroxide. But bottom line, the oxygen is not happy, his octet is satisfied, but it is not in it's lowest energy form. You will probably never see a stable oxygen with that bonding pattern. The oxygen will either kick of the hydrogen or break the pi bond with the carbon. This will allow his electrons to go into the lowest energy orientation and keep his octet.

I am pretty sure thats the reason. It's the only thing that makes sense to me.

 

[dantemac]

Yeah, that structure is possible but the O would need a +1 charge.

 

[yappy]

ahh I see. It looked odd to me... and seems unfavorable becasue of the +1 formal charge on the Oxygen; however, it seems inaccurate to call it "impossible".

I say this because it could be a possible resonance structure - even though it's very unfavorable?


note* I'm assuming there is a LP on the oxygen.

 

[Juggernauts]

I think your correct, "unfavorable" is the probably the accurate descriptor here. "Impossible" is the word used in the actual problem.

 

[anguye48]

Oxygen can never have more than 2 bonds around it. Referring to its electron configuration as well as hybridization theory and you'll understand why.

 

[yappy]

Can you unpack this a little bit for me? I would really like to understand this problem.

It looks like the oxygen has two sigma bonds and one pi. Because it doesnt have a 'real' charge notation I'll assume it has a lone pair too. Therefore, it has 3 hybrid connections of sp2. This leaves an extra unhybrid P orbital open for pi bonding. Does this contribute to the structure not being possible?

Or are you saying it has to do with oxygen being in the 6a group that it cannot make more than two-bonds-around-it?

Oxygen can never have more than 2 bonds around it. Referring to its electron configuration as well as hybridization theory and you'll understand why.

 

[anguye48]

Oxygen has 6 valence electrons to start with and its outermost shell is 2nd shell. Use Pauli principle to assign the valence e to the hybridized orbitals:

In the case of sp2 hybridization: The hybridization of Oxygen will end up with 2 fully occupied sp2 orbital, 1 half-full sp2 orbital and one half-full p orbital. the half-full sp2 orbital can make 1 sigma bond and the half-full p orbital can make 1 pi bond. One sigma+one pi= 1 double bond.

If oxygen is sp3 hybridized to make single bond, 6 valence e- will distributed as follow: two full sp3 orbital and two half-full sp3 orbital. Only the 2 half-full can accept 2 more e- from other atoms which will result in 2 single bonds around Oxygen.

Being in the 6A column has nothing to do with the fact that Oxygen can only have 2 bonds cuz if you add another shell (in the case of Sulfur which is also in the 6A column), it will affect hybridization as well. And yes, S can have many bonds around it ( I believe up to 6 bonds)

I hope this help cuz i don't know how to make it clearer.

 

[anguye48]

So *impossible* seems to be the right word in this case 🙂

 

[Jackson-Ave-Dental]

Must be polar covalent with a hydrogen bond.

 

[adianadiadi]

Look at oxygen. It has 3 bonds. And it is not allowed since for oxygen, the valency is 2 only.

 

[Jackson-Ave-Dental]

http://en.wikipedia.org/wiki/Ozone

 

[Balkoth0069]

So what IS an impossible bond, in and of itself, are there any two or more molecules that absolutely can not bond?