Question

Which of the following correctly represents the acidic strength of given acids?
1. $C{l}_{3}CH>F_{3}CH$
2.$C{H}_{3}COOH>C{H}_{3}C{H}_{2}OH$
3. $H_{2}O>C{H}_{3}C{H}_{2}OH$
4. $\text{p-nitrophenol}>\text{phenol}$

• A. (1) and (2)
• B. (1) and (3)
• C. (2), (3) and (4)
• D. (1), (2), (3) and (4)

Answer 1

The correct option is D (1), (2), (3) and (4)

Most acidic will be the species when its conjugate base is most stibilised.
(1) The negative charge in $F_3{C}^{-}$ is stabilized by the inductive effect by $F$ while the $C{l}_3{C}^{-}$ is stabilized by the resonance effect in which the negative charge is delocalized in the vacant d-orbitals of $Cl$ atoms.

(2) Carboxylic acid is more acidic than alcohol due to resonance stabilised carboxylate ion.

(3) $H{O}^{-}$ is weaker base than $C{H}_{3}C{H}_2{O}^{-}$ due to $+I$ effect shown by ethyl group in later.

(4) Negative charge on $O$ in phenoxide ion is stabilised furthur by $-N{O}_2$ which shows strong $-R$ effect.