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Aldehydes Ketones and Carboxylic Acids question

2019 · 9 Apr · Shift 2 · Q1
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Aldehydes Ketones and Carboxylic Acids question

2019 · 9 Apr · Shift 2 · Q1

JEE MainChemistryAldehydes Ketones and Carboxylic AcidsMCQ+4 / −1
p-Hydroxybenzophenone upon reaction with bromine in carbon tetrachloride gives:
  1. A
    JEE Main 2019 (Online) 9th April Evening Slot Chemistry - Aldehydes, Ketones and Carboxylic Acids Question 189 English Option 1
  2. B
    JEE Main 2019 (Online) 9th April Evening Slot Chemistry - Aldehydes, Ketones and Carboxylic Acids Question 189 English Option 2
  3. C
    JEE Main 2019 (Online) 9th April Evening Slot Chemistry - Aldehydes, Ketones and Carboxylic Acids Question 189 English Option 3
  4. D
    JEE Main 2019 (Online) 9th April Evening Slot Chemistry - Aldehydes, Ketones and Carboxylic Acids Question 189 English Option 4
View written solutionFree

Correct answer: B

  1. Identify the substrate

    ppp-Hydroxybenzophenone is benzophenone with an −OH-OH−OH group para to the carbonyl-linked phenyl bond on one ring.

    Its structure can be viewed as: HO−C6H4−CO−C6H5\mathrm{HO{-}C_6H_4{-}CO{-}C_6H_5}HO−C6​H4​−CO−C6​H5​ where the −OH-OH−OH is para on the left ring.

  2. Nature of the reagent

    Bromine in carbon tetrachloride, Br2/CCl4\mathrm{Br_2/CCl_4}Br2​/CCl4​, is a non-polar brominating reagent. It typically causes electrophilic bromination on activated aromatic rings.

    Since no Lewis acid like FeBr3\mathrm{FeBr_3}FeBr3​ is mentioned, bromination will occur preferentially on the more activated ring.

  3. Effect of substituents on the aromatic ring

    On the hydroxy-substituted ring, there are two substituents:

    • −OH-OH−OH: strongly activating, ortho/para directing
    • −COPh-COPh−COPh: deactivating, meta directing

    The −OH-OH−OH group dominates activation and directs bromination to its ortho/para positions.

  4. Available positions for substitution

    In ppp-hydroxybenzophenone, the para position to −OH-OH−OH is already occupied by the −COPh-COPh−COPh group. So bromination can occur only at the two ortho positions to −OH-OH−OH.

    These are positions 2 and 6 of the ring, and due to symmetry they are equivalent.

  5. Product formed

    Therefore, monobromination gives: 2-bromo-4-hydroxybenzophenone\mathrm{2\text{-}bromo\text{-}4\text{-}hydroxybenzophenone}2-bromo-4-hydroxybenzophenone

    Since positions 2 and 6 are equivalent, only one monobromo product is formed.

  6. Conclusion

    So the correct option is the one showing bromination ortho to the phenolic −OH-OH−OH group on the hydroxy-containing ring.

    Hence, the answer is Option B.

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