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Haloalkanes and Haloarenes question

2025 · 28 Jan · Shift 1 · Q7
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Haloalkanes and Haloarenes question

2025 · 28 Jan · Shift 1 · Q7

JEE MainChemistryHaloalkanes and HaloarenesMCQ+4 / −1
The products A and B in the following reactions, respectively are A⟷Ag−NO2CH3−CH2−CH2−Br→AgCNB\mathrm{A} \stackrel{\mathrm{Ag}-\mathrm{NO}_2}{\longleftrightarrow} \mathrm{CH}_3-\mathrm{CH}_2-\mathrm{CH}_2-\mathrm{Br} \xrightarrow{\mathrm{AgCN}} \mathrm{B}A⟷Ag−NO2​​CH3​−CH2​−CH2​−BrAgCN​B
  1. A
    CH3−CH2−CH2−ONO,CH3−CH2−CH2−CN\mathrm{CH}_3-\mathrm{CH}_2-\mathrm{CH}_2-\mathrm{ONO}, \mathrm{CH}_3-\mathrm{CH}_2-\mathrm{CH}_2-\mathrm{CN}CH3​−CH2​−CH2​−ONO,CH3​−CH2​−CH2​−CN
  2. B
    CH3−CH2−CH2−NO2,CH3−CH2−CH2−CN\mathrm{CH}_3-\mathrm{CH}_2-\mathrm{CH}_2-\mathrm{NO}_2, \mathrm{CH}_3-\mathrm{CH}_2-\mathrm{CH}_2-\mathrm{CN}CH3​−CH2​−CH2​−NO2​,CH3​−CH2​−CH2​−CN
  3. C
    CH3−CH2−CH2−ONO,CH3−CH2−CH2−NC\mathrm{CH}_3-\mathrm{CH}_2-\mathrm{CH}_2-\mathrm{ONO}, \mathrm{CH}_3-\mathrm{CH}_2-\mathrm{CH}_2-\mathrm{NC}CH3​−CH2​−CH2​−ONO,CH3​−CH2​−CH2​−NC
  4. D
    CH3−CH2−CH2−NO2,CH3−CH2−CH2−NC\mathrm{CH}_3-\mathrm{CH}_2-\mathrm{CH}_2-\mathrm{NO}_2, \mathrm{CH}_3-\mathrm{CH}_2-\mathrm{CH}_2-\mathrm{NC}CH3​−CH2​−CH2​−NO2​,CH3​−CH2​−CH2​−NC
View written solutionFree

Correct answer: D

  1. We need to identify the products formed when 111-bromopropane, CH3−CH2−CH2−Br\mathrm{CH_3-CH_2-CH_2-Br}CH3​−CH2​−CH2​−Br, reacts with:

    • AgNO2\mathrm{AgNO_2}AgNO2​
    • AgCN\mathrm{AgCN}AgCN

  2. Reaction with AgNO2\mathrm{AgNO_2}AgNO2​

    The nitrite ion NO2−\mathrm{NO_2^-}NO2−​ is an ambident nucleophile and can attack through either:

    • oxygen: giving alkyl nitrite R−ONO\mathrm{R-ONO}R−ONO
    • nitrogen: giving nitroalkane R−NO2\mathrm{R-NO_2}R−NO2​

    But with silver nitrite AgNO2\mathrm{AgNO_2}AgNO2​, the bonding is more covalent, and substitution occurs predominantly through nitrogen, giving a nitroalkane.

    Hence,

    CH3−CH2−CH2−Br→AgNO2CH3−CH2−CH2−NO2\mathrm{CH_3-CH_2-CH_2-Br \xrightarrow{AgNO_2} CH_3-CH_2-CH_2-NO_2}CH3​−CH2​−CH2​−BrAgNO2​​CH3​−CH2​−CH2​−NO2​

    So, A=CH3−CH2−CH2−NO2A = \mathrm{CH_3-CH_2-CH_2-NO_2}A=CH3​−CH2​−CH2​−NO2​

  3. Reaction with AgCN\mathrm{AgCN}AgCN

    The cyanide ion CN−\mathrm{CN^-}CN− is also an ambident nucleophile and can attack through either:

    • carbon: giving nitrile R−CN\mathrm{R-CN}R−CN
    • nitrogen: giving isocyanide R−NC\mathrm{R-NC}R−NC

    With KCN, ionic character dominates, so attack occurs through carbon to give nitrile.

    With AgCN, due to covalent character, substitution occurs through nitrogen, giving isocyanide.

    Therefore,

    CH3−CH2−CH2−Br→AgCNCH3−CH2−CH2−NC\mathrm{CH_3-CH_2-CH_2-Br \xrightarrow{AgCN} CH_3-CH_2-CH_2-NC}CH3​−CH2​−CH2​−BrAgCN​CH3​−CH2​−CH2​−NC

    So, B=CH3−CH2−CH2−NCB = \mathrm{CH_3-CH_2-CH_2-NC}B=CH3​−CH2​−CH2​−NC

  4. Therefore the pair (A,B)(A,B)(A,B) is:

    CH3−CH2−CH2−NO2,CH3−CH2−CH2−NC\mathrm{CH_3-CH_2-CH_2-NO_2,\\ CH_3-CH_2-CH_2-NC}CH3​−CH2​−CH2​−NO2​,CH3​−CH2​−CH2​−NC

  5. Option matching

    • A: R−ONO,R−CN\mathrm{R-ONO, R-CN}R−ONO,R−CN ❌
    • B: R−NO2,R−CN\mathrm{R-NO_2, R-CN}R−NO2​,R−CN ❌
    • C: R−ONO,R−NC\mathrm{R-ONO, R-NC}R−ONO,R−NC ❌
    • D: R−NO2,R−NC\mathrm{R-NO_2, R-NC}R−NO2​,R−NC ✅

Thus, the correct option is D.

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