Q7 · CSIR-NET Chemistry, June 2016
Paper: CSIR-NET June 2016 · Subject: Organic Chemistry · Chapter: Natural Products · Topic: Natural Products – General · Marks: 2 · Difficulty: Medium
At pH 10, tryptophan exists as
(a)
(b)
(c)
(d)
Answer
Answer: A ✓ checked by 4AB · confidence high
Explanation
At pH 10 the carboxylic acid (pKa 2.4) is a carboxylate and the α-amino group (pKa 9.4) is mostly deprotonated, so tryptophan is the anion with free NH₂ (a); the indole N–H (pKa ≈ 17) stays neutral.
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