QJEEAdv20Chc0e3: JEE Advanced 2020 Chemistry - Class 11 JEEAdv20Chc0e3 Solution: With respect to the compounds I-V, choose the correct…
With respect to the compounds I-V, choose the correct statement(s).
Multiple Choice Options
AThe acidity of compound I is due to delocalisation in the conjugate base.
BThe conjugate base of compound IV is aromatic.
CCompound II becomes more acidic, when it has a − NO2 substituent.
DThe acidity of compounds follows the orderI > IV > V > II > III.
Step-by-Step Verified Solution
Triphenylmethane (I) is acidic because its conjugate base is stabilised by resonance.
Cyclopentadiene (IV) is acidic because its conjugate base is aromatic.
Nitrobenzene is more acidic than benzene because nitro group is electron withdrawing. It will stabilise the conjugate base of benzene by −R and −I effect.
The acidic strength order on the basis of pKa data is
IV > V > I > II > III.
Hence, the correct options are (a), (b) and (c) only.
