Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: sailpatrick on September 28, 2009, 07:57:26 AM
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Hey guys!
I have a question regarding this amino acid : O
|| (pK1=2.2)
H2N --- C---NH---CH2---CH2---CH2---CH--C---OH
| |
NH2 NH3 (pK2 =9)
pK3=12.5)
I need to know why these 2 answers would be incorrect ( with explanation) regarding the above aa
1) the net charge is -1 within the pH range 2.2-9.0
edit: the forum doesn't seem to keep my drawing in place with the substituents so the NH2 belongs under the first C from the left and the NH3 belongs under the first CH from the right and the double bonded O of course belongs above the first C from the right . Sorry about the confusion
2) the form of amino acid shown predominates for pH>2.2
Thanks a bunch!
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First consider what the protonated and deprotonated forms of the amine and carboxylic acid groups look like and what charge they have.
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Do you know what the pK represents? What happens when pH = pK?