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Basics of Organic Chemistry question

2021 · 22 Jul · Shift 2 · Q4
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Basics of Organic Chemistry question

2021 · 22 Jul · Shift 2 · Q4

JEE MainChemistryBasics of Organic ChemistryMCQ+4 / −1
Which of the following compounds does not exhibit resonance?
  1. A
    CH3CH2OCH=CH2CH_3CH_2OCH=CH_2CH3​CH2​OCH=CH2​
  2. B
    JEE Main 2021 (Online) 22th July Evening Shift Chemistry - Basics of Organic Chemistry Question 163 English Option 2
  3. C
    CH3CH2CH2CONH2CH_3CH_2CH_2CONH_2CH3​CH2​CH2​CONH2​
  4. D
    CH3CH2CH=CHCH2NH2CH_3CH_2CH=CHCH_2NH_2CH3​CH2​CH=CHCH2​NH2​
View written solutionFree

Correct answer: D

  1. Identify the condition for resonance

    Resonance is shown by compounds in which there is conjugation, i.e. adjacent atoms with:

    • a π\piπ bond next to another π\piπ bond, or
    • a lone pair next to a π\piπ bond, or
    • a charge next to a π\piπ bond.

    So we check whether each compound has such delocalization.

  2. Option A: CH3CH2OCH=CH2CH_3CH_2OCH=CH_2CH3​CH2​OCH=CH2​

    Structure can be written as: CH3CH2−O−CH=CH2CH_3CH_2-O-CH=CH_2CH3​CH2​−O−CH=CH2​

    Here oxygen has a lone pair adjacent to the double bond: −O−CH=CH2-O-CH=CH_2−O−CH=CH2​

    Therefore, resonance is possible by donation of lone pair from oxygen into the adjacent π\piπ system: CH3CH2−O−CH=CH2↔CH3CH2−O+=CH−CH2−CH_3CH_2-O-CH=CH_2 \leftrightarrow CH_3CH_2-O^+=CH-CH_2^-CH3​CH2​−O−CH=CH2​↔CH3​CH2​−O+=CH−CH2−​

    So A exhibits resonance.

  3. Option C: CH3CH2CH2CONH2CH_3CH_2CH_2CONH_2CH3​CH2​CH2​CONH2​

    This is an amide: CH3CH2CH2−C(=O)−NH2CH_3CH_2CH_2-C(=O)-NH_2CH3​CH2​CH2​−C(=O)−NH2​

    In amides, the lone pair on nitrogen is conjugated with the carbonyl group: R−C(=O)−NH2↔R−C(−O−)=NH2+R-C(=O)-NH_2 \leftrightarrow R-C(-O^-)=NH_2^+R−C(=O)−NH2​↔R−C(−O−)=NH2+​

    Hence C exhibits resonance strongly.

  4. Option D: CH3CH2CH=CHCH2NH2CH_3CH_2CH=CHCH_2NH_2CH3​CH2​CH=CHCH2​NH2​

    Structure: CH3CH2−CH=CH−CH2NH2CH_3CH_2-CH=CH-CH_2NH_2CH3​CH2​−CH=CH−CH2​NH2​

    The NH2NH_2NH2​ group is attached to a CH2CH_2CH2​ carbon, not directly to the double bond carbon.

    So the arrangement is: C=C−CH2−NH2C=C-CH_2-NH_2C=C−CH2​−NH2​

    Because of the intervening saturated CH2CH_2CH2​ carbon, the lone pair on nitrogen is not adjacent to the double bond. Thus there is no conjugation and hence no resonance involving the given functional groups.

    So D does not exhibit resonance.

  5. Conclusion

    The compound that does not exhibit resonance is: D\boxed{D}D​

  6. Comparison with stored answer

    Stored correct answer = D.

    My derived answer = D.

    Therefore, they agree.

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