[rleung]

Hey,

I am confused as to why the reactants are the stronger acids and bases in the following reaction:

CH3N(+)H3 + CH30(-) ---> CH3NH2 + CH3OH

I would have thought that the stronger acid was CH3OH and the stronger base was CH3NH2.  First, I compared the acids.  The acids are CH3N(+)H3 and CH3OH.  Since O is more electronegative, I would think that the molecule with the more electrognegative element would be a stronger acid.  As for comparing the bases CH30(-)  and CH3NH2, since N is less electronegative than O, I would think CH3NH2 is the stronger base.  

Thanks so much for the help.

Ryan

[movies]

Electronegativity is a good place to start, but you have to make sure you are comparing apples to apples.

In general, charged molecules are higher in energy than neutral ones, so you could infer that the protonated amine is higher in energy than methanol, right?  So a charged acid is different from a neutral acid just based on the starting energy of the molecules.  It's apples and oranges!

Using electronegativity is a sound method when you compare two charged molecules to one another or two neutral molecules to one another.

Does that help?

[Mitch]

You can also compare k values. It should be in your book somewhere.

[rleung]

Thanks for your help.

Is there a way to tell which is the stronger acid and base then without comparing the K values?  I ask because the problem asks us to name the strong acid and strong base.

[maivanganh]

According to Lewis, i think CH3O(-) is a stronger base than CH3NH2 can be because it can give its lone pair very easy. And acid CH3N(+)H3 is tronger than CH3OH because it can release proton easier to become an uncharged molecule. So strong acid + strong base => weak acid (CH3OH) + weak base (CH3NH2)
Is it ok?

[Winga]

If you want to compare the basicity of CH3O- with CH3NH- (not CH3NH2), using the difference in electronegativity to explain is a good start across the same period.

[arnyk]

Either way, none of those would be considered "strong" acids or bases.