Define zwitterion. At what pH condition does glycine exist as a zwitterion — JEE Chemistry
Define zwitterion. At what pH condition does glycine exist as a zwitterion? ($pK_{a1} = 2.34$, $pK_{a2} = 9.60$)
1 Answer
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· 21d ago
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A zwitterion is a molecule with both positive and negative charges, with net zero charge:
$$H_3N^+-CH_2-COO^-$$
The isoelectric point (pI) is the pH at which the zwitterion predominates:
$$pI = \frac{pK_{a1} + pK_{a2}}{2} = \frac{2.34 + 9.60}{2} = 5.97$$
At pH = 5.97, glycine is electrically neutral and exists predominantly as the zwitterion.
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Discussion (2)
RB
Pro tip: memorise the standard result, it reappears in many problems.
TS
Quick doubt: would this method still work if the numbers were not so clean?