Q.Identify the weakest acidic compound amongst the following:

Phenol ionises to a modest extent in water because its conjugate base, the phenoxide ion, is resonance-stabilised: the oxygen's negative charge delocalises into the aromatic ring, spread over the ortho and para ring carbons through five resonance contributing structures. An alcohol's conjugate base (alkoxide), by contrast, has no such delocalisation and is instead destabilised by the electron-donating inductive (+I) effect of its alkyl group, so alcohols remain essentially neutral in water. This difference is confirmed by two laboratory tests: phenol turns blue litmus red and dissolves in NaOH (though not the weaker base NaHCO3), while alcohols do neither. Ring substituents further shift phenol's acid strength relative to plain phenol: electron-withdrawing groups (like -NO2 …