Q107 · 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
pH 10 is above the α-NH₃⁺ pKa (≈9.4) and far above the COOH pKa (≈2.4) but below the indole N–H pKa (~17). Tryptophan is therefore mainly the anion H₂N–CH(R)–COO⁻ (a).
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