Why does oxygen carry the positive F.C in [CH3OH2]+?

In summary, the Lewis structure for [CH3OH2]+ has a positive formal charge on the oxygen, despite its higher electronegativity. This results in a polar covalent bond between carbon and oxygen. According to basic Lewis structure rules, the most electronegative atom should carry the negative formal charge, but in this case, it is the carbon atom that carries the positive charge. The structure can be found by starting with CH3OH and then adding a lone pair on oxygen to accommodate the extra H+ ion.
  • #1
fridakahlo
10
1

Homework Statement


Find the lewis structure for [CH3OH2]+

Homework Equations


n/a

The Attempt at a Solution


I found the lewis structure to have a positive formal charge on the oxygen. I'm not sure why the oxygen would have the + f.c. since it is much more electronegative than fairly neutral carbon. I initially wanted carbon to have an incomplete octet, so it would carry the + charge, but that did not work.
 
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  • #2
I just looked up the electronegativity difference (Pauling scale) for Carbon and oxygen=0.9

So... this would be a polar covalent bond.

However, basic lewis structure rules say that the most electronegative atom should carry the negative formal charge. Right?
 
  • #3
Start with CH3OH, then look for a lone pair which can hold H+.
 

FAQ: Why does oxygen carry the positive F.C in [CH3OH2]+?

1. What is the role of oxygen in [CH3OH2]+?

The oxygen in [CH3OH2]+ plays a crucial role in carrying the positive formal charge (F.C). Oxygen has a high electronegativity, meaning it has a strong attraction for electrons. This allows it to hold onto the positive F.C and stabilize the overall charge of the molecule.

2. Why does oxygen carry the positive F.C instead of carbon?

Oxygen is more electronegative than carbon, making it more capable of holding onto the positive F.C. Additionally, oxygen is able to accommodate a larger number of electrons in its valence shell compared to carbon. This allows it to distribute the charge more effectively, making it a better candidate for carrying the positive F.C.

3. How does the structure of [CH3OH2]+ contribute to the positive F.C on oxygen?

The structure of [CH3OH2]+, also known as methoxonium ion, has three hydrogen atoms bonded to the oxygen atom. This creates a highly polarized bond between the hydrogen and oxygen atoms, with the oxygen atom bearing a partial positive charge. This partial positive charge on oxygen contributes to the overall positive F.C on the molecule.

4. Can the positive F.C on oxygen in [CH3OH2]+ be delocalized?

Yes, the positive F.C on oxygen in [CH3OH2]+ can be delocalized. This means that the charge can be spread out over multiple atoms, rather than being localized on just one atom. In this case, the positive F.C can be delocalized to the adjacent carbon atom, creating a more stable overall charge distribution.

5. Does the positive F.C on oxygen in [CH3OH2]+ affect the reactivity of the molecule?

Yes, the positive F.C on oxygen in [CH3OH2]+ can affect the reactivity of the molecule. The presence of a positive charge on an atom can make it more reactive, as it is seeking to gain electrons and become neutral. This makes [CH3OH2]+ more susceptible to reactions with other molecules or ions that can donate electrons to stabilize the charge.

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