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

[fridakahlo]

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.

 

[fridakahlo]

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?

 

[Borek]

Start with CH₃OH, then look for a lone pair which can hold H⁺.