Which end of glycine would be more basic?

[Avi_R]

I had a question given, regarding the basicity of certain sites on a molecule. For example, glycine:

How would you determine whether the OH end or the NH2 end would be more "basic", or the first to get protonated?

 

[lightarrow]

I had a question given, regarding the basicity of certain sites on a molecule. For example, glycine:

How would you determine whether the OH end or the NH2 end would be more "basic", or the first to get protonated?

Make an analogy and think about

1. CH3-OH
2. CH3-NH2

Which is more protonable?
In case you didn't find the answer, try with

1. H-OH = H2O
2. H-NH2 = NH3

Which is more protonable?

 

[Avi_R]

What I'd like to know is how do I determine which is more protonable, without memorizing pka's.

 

[siddharth]

For the amino acids, one end has a carboxyl group (ie COOH) and the other end has the amino group. So, in this case, it's easy to figure out which end is acidic (ie, loses H+) and which end is basic (ie, accepts H+).