0
$\begingroup$

enter image description here

On the 3rd diagram (from left), the one with net charge = -1 ,

Why did it lose the H to OH- from the CH2CO2H from the neutral form ?

I was told that while moving to the right , the OH- will take H+ electrons meaning it should take H+ from NH3 .. ?

Is there any reason why they took the H from CH2CO2H ?

Any help would be appreciated!

$\endgroup$
3
$\begingroup$

The -CO₂H groups are carboxylic acid groups, better represented as -COOH. These, being acidic, have a lower pKₐ than the -NH₃⁺ group and so as the pH increases these -COOH groups lose their protons first.

The pKₐ values for the three are shown below the arrows: as you can see the α carboxylic acid is more acidic than that in the side chain, but they are both much more acidic than the protonated amino group.

$\endgroup$

Not the answer you're looking for? Browse other questions tagged or ask your own question.