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Biomolecules question

2020 · 4 Sep · Shift 1 · Q4
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Biomolecules question

2020 · 4 Sep · Shift 1 · Q4

JEE MainChemistryBiomoleculesMCQ+4 / −1
Which of the following will react with CHCl3CHCl_3CHCl3​ + alc. KOHKOHKOH?
  1. A
    Adenine and thymine
  2. B
    Thymine and proline
  3. C
    Adenine and lysine
  4. D
    Adenine and proline
View written solutionFree

Correct answer: C

  1. Identify the reagent

    CHCl3+CHCl_3 +CHCl3​+ alcoholic KOHKOHKOH generates dichlorocarbene and is used in the carbylamine test.

    The carbylamine test is given by primary amines only: RNH2+CHCl3+3KOH→RNC+3KCl+3H2ORNH_2 + CHCl_3 + 3KOH \rightarrow RNC + 3KCl + 3H_2ORNH2​+CHCl3​+3KOH→RNC+3KCl+3H2​O So we must find which biomolecules contain a free primary amino group that can respond.

  2. Check each compound

    • Adenine: It is a purine base containing an exocyclic −NH2-NH_2−NH2​ group at the 6-position. This behaves as a primary amino group, so adenine gives the test.
    • Thymine: It is a pyrimidine base with no amino group; it has carbonyl groups instead. So does not react.
    • Proline: It is an amino acid, but its amino group is secondary because it is part of a pyrrolidine ring (imino acid). Secondary amines do not give carbylamine test.
    • Lysine: It has two amino groups, including a free side-chain −NH2-NH_2−NH2​ primary amino group. Hence reacts.
  3. Evaluate options

    • A: Adenine and thymine
      Thymine does not react. So this is incorrect.

    • B: Thymine and proline
      Thymine does not react, and proline is secondary amine. So incorrect.

    • C: Adenine and lysine
      Both contain primary amino groups. So correct.

    • D: Adenine and proline
      Proline does not give carbylamine test. So incorrect.

  4. Final answer

    The compounds that react with CHCl3+CHCl_3 +CHCl3​+ alc. KOHKOHKOH are: Adenine and lysine\boxed{\text{Adenine and lysine}}Adenine and lysine​ Hence, Option C is correct.

  5. Comparison with stored correct answer

    Stored correct answer = C
    Derived answer = C
    Therefore, they agree.

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