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Practical Organic Chemistry question

2021 · 18 Mar · Shift 1 · Q4
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Practical Organic Chemistry question

2021 · 18 Mar · Shift 1 · Q4

JEE MainChemistryPractical Organic ChemistryMCQ+4 / −1
Reagent, 1-napthylamine and sulphanilic acid in acetic acid is used for the detection of
  1. A
    N2ON_2ON2​O
  2. B
    NO 3−_3^ -3−​
  3. C
    NO
  4. D
    NO 2−_2^ -2−​
View written solutionFree

Correct answer: D

  1. Identify the reagent mentioned

    The combination of 1-naphthylamine and sulphanilic acid in acetic acid is the classical Griess reagent.

  2. What does Griess reagent detect?

    Griess reagent is used for the detection of nitrite ions, NO2−\mathrm{NO_2^-}NO2−​.

  3. Principle of the test

    • In acidic medium, nitrite forms nitrous acid: NO2−+H+→HNO2\mathrm{NO_2^- + H^+ \rightarrow HNO_2}NO2−​+H+→HNO2​
    • This nitrous acid diazotizes sulphanilic acid.
    • The diazonium salt then couples with 1-naphthylamine to form a colored azo dye.
    • Formation of this dye indicates the presence of nitrite.

  4. Check each option

    • A: N2ON_2ON2​O — not detected by this reagent.
    • B: NO3−NO_3^-NO3−​ — nitrate does not directly respond unless first reduced to nitrite.
    • C: NONONO — not the standard detection by this reagent.
    • D: NO2−NO_2^-NO2−​ — correct.

  5. Conclusion

    Therefore, the reagent is used for detecting: NO2−\boxed{\mathrm{NO_2^-}}NO2−​​

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