Glycine at pH 7.0?

[DenTony11235]

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Glycine is amphoteric, both acidic and Basic properties. It has an amine on one side and a carboxy acid on the other. At pH 7.0, it's amine is protonated while its carboxy acid side is de-protonated. Why?

 

[hl4jn]

When you're thinking about acids and bases and what is protonated and not, you always have to compare the pH of the solution to the pKa of the functional group in question. In general, if the pH is higher than the pKa , the functional group is deprotonated. If the pH is lower than the pKa, the functional group is protonated.

If you think about it, the higher the pKa and pH, the more basic it is so the higher thing is going to act as a base.

 

[IsaacYankem]

Piggybacking of what hl4jn said which is correct,

NH2 has a pka ~9.3 so at pH 7 it's in acid form (NH3+), whereas the carboxylic acid has a pKa ~2, so at pH at 7, it will be in the carboxylate form (COO-)

Hope that helps

 

[DenTony11235]

Ah got it, thanks