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Ionic Species With Alanine?
Write the structure of the ionic species of the amino acid alanine when it is in a solution of having a pH 5 and a in a solution of a pH 9.
pKa of alanine carboxyl group=2.3
pKa of alanine amino group=9.7
1 Answer
- Sam SaunLv 68 years agoFavorite Answer
The isoelectric point of alanine is (5+9)/2 = 7, hence at pH 7 the switterion +NH3C(CH3)CO2- will persist. At values lower than 7 the carboxylic acid will be protonated and at pH values higher than 7 the amine will be deprotonated:
+NH3C(CH3)CO2H at pH 5 and NH2C(CH3)CO2- at pH 9