Alcohol, Phenol and Ether MCQ Questions & Answers in Organic Chemistry | Chemistry

\[C{{H}_{3}}\underset{\begin{smallmatrix} |\,\,\,\,\,\, \\ OH\,\,\, \\ \left( X \right) \end{smallmatrix}}{\mathop{-CH-}}\,C{{H}_{3}}\]
\[\underset{\left( Y \right)}{\overset{\,\,\,\,\,\,\,\,\left[ O \right]\downarrow }{\mathop{C{{H}_{3}}COC{{H}_{3}}}}}\,\xrightarrow[\frac{{{H}^{+}}}{{{H}_{2}}O}]{C{{H}_{3}}MgBr}\]     \[\underset{\begin{smallmatrix} \text{2-Metbylpropan-2-ol} \\ \left( Z \right) \end{smallmatrix}}{\mathop{C{{H}_{3}}\underset{\begin{smallmatrix} | \\ \,\,\,\,C{{H}_{3}} \end{smallmatrix}}{\overset{\begin{smallmatrix} \,\,\,\,C{{H}_{3}} \\ | \end{smallmatrix}}{\mathop{-C-}}}\,OH}}\,\]

\[\underset{\text{3-Methylbut-l-ene}}{\mathop{C{{H}_{3}}\underset{\begin{smallmatrix} |\,\,\,\,\, \\ C{{H}_{3}}\,\, \end{smallmatrix}}{\mathop{-CH-}}\,CH}}\,=C{{H}_{2}}\xrightarrow[{{H}^{+}}]{{{H}_{2}}O}\]      \[\underset{\text{3-Methylbufan-2-ol}}{\mathop{\underset{\begin{smallmatrix} \,\,\,\,\,\,| \\ \,\,\,\,\,\,\,\,\,C{{H}_{3}} \end{smallmatrix}}{\mathop{C{{H}_{3}}CH}}\,\underset{\begin{smallmatrix} |\,\,\,\,\,\, \\ OH\,\,\, \end{smallmatrix}}{\mathop{-CH-}}\,C{{H}_{3}}}}\,\]
The addition of \[{{H}_{2}}O\]  in presence of acid takes place according to Markovnikov's rule.

The tertiary carbocation formed during dehydration of 2-methyl-2-propanol is most stable.

$$ZnC{l_2} + conc.\,HCl$$     is Lucas reagent. Lucas reagent reacts fastest with tertiary alcohol. $${3^ \circ }$$ alcohol + Lucas reagent = Immediate turbidity

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Key Idea Higher the tendency to give a proton, higher is the acidic character and tendency to lose a proton depends upon the stability of intermediate, i.e. carbanion formed.
2, 4, 6 - trinitrophenol after the loss of a proton gives 2, 4, 6 - trinitrophenoxide ion which is stabilised by resonance, $$-I$$ - effect and $$-M$$ - effect, thus is most acidic among the given compounds.
Phenol after losing a proton form phenoxide ion which is also stabilised by resonance, $$-M$$  and $$-I$$ effects but is less stabilised as compared to 2, 4, 6 - trinitrophenoxide ions. Thus, it is less acidic as compared to 2, 4, 6 - trinitrophenol, $$\left( {C{H_3}COOH} \right)$$   after losing a proton gives acetate
ion which is stabilised by only resonance. However, it is more resonance stabilised as compared to a phenoxide ion, thus more acidic as compared to phenol. 2, 4, 6 - trinitrophenol, however, is more acidic than acetic acid due to the presence of three electron withdrawing $$ - N{O_2}$$  group. Cyclohexanol gives an anion that is least stable among the given, thus, it is least acidic.
Hence, the correct order of acidic strength is 2, 4, 6 - trinitrophenl > acetic acid > phenol > cyclohexanol
(iii) > (ii) > (iv) > (i)