Halogens have both $$+R$$ and $$-I$$ effect, but the $$-I$$ effect predominates over the $$+ R$$ - effect. Therefore, $$m$$ - chlorophenol is most acidic due to electron withdrawing $$- Cl$$ group. Alcohols are less acidic than phenol.
233.
When phenol is reacted with $$CHC{l_3}$$ and $$NaOH$$ followed by acidification, salicyladehyde is obtained. Which of the following species are involved in the above mentioned reaction as intermediate?
Temperature is the effective factor for dehydration of alcohol by $$A{l_2}{O_3}$$ ( dehydrating reagent ).
\[R-C{{H}_{2}}-C{{H}_{2}}OH\xrightarrow[{{350}^{\circ }}-{{380}^{\circ }}C]{A{{l}_{2}}{{O}_{3}}}R-CH=C{{H}_{2}}+{{H}_{2}}O\]
While at $${220^ \circ } - {250^ \circ }C,$$ it forms ether.
235.
On reaction with sodium, $$1\,mol$$ of a compound $$X$$ gives $$1\,mol$$ of $${H_2}.$$ Which one of the following compounds might be $$X?$$
A
$$C{H_3}C{H_2}CH = C{H_2}$$
B
$$C{H_3}COOC{H_2}C{H_3}$$
C
$$C{H_3}C{H_2}C{H_2}OH$$
D
$$C{H_2}\left( {OH} \right)C{H_2}C{H_2}C{H_2}OH$$
Since $$1\,mole$$ of compound $$X$$ reacts with $$Na$$ to evolve $$1\,mole$$ of $${H_2}$$ gas, therefore the compound should have 2 active hydrogen atoms per mole which is possible only in option $$d.$$
$$C{H_2}OHC{H_2}C{H_2}C{H_2}OH + 2Na \to NaOC{H_2}C{H_2}C{H_2}C{H_2}ONa + 2H$$
236.
A compound $$(A)$$ of molecular formula $${C_7}{H_8}O$$ is insoluble in water and dilute sodium bicarbonate but dissolves in dilute aqueous sodium hydroxide and gives a characteristic colour with aqueous $$FeC{l_3}.$$ On treatment with bromine water, it readily gives a precipitate of $${C_7}{H_5}OB{r_3}.$$ Write down the structure of the compound $$(A).$$
(i) Since $$A$$ gives characteristic colour with aqueous $$FeC{l_3}$$ so it contains a phenolic group.
(ii) Since $$A$$ when treated with $$B{r_2}$$ forms $${C_7}{H_5}OB{r_3}$$ (ppt.) and considering the molecular formula of $$A,$$ it is most likely to be cresol.
(iii) Since $$A$$ on bromination forms tribromo derivative so, it is $$m$$ - cresol i.e.
The reactions are :
237.
$$n$$ - propyl alcohol and isopropyl alcohol can be chemically distinguished by which reagent
In such reactions, first write down the sequence of reactions and then proceed backward/forward from a known compound, reagent, or known fact (test).
\[A\xrightarrow[\left( ii \right)\,{{H}_{2}}O]{\left( i \right)\,C{{H}_{3}}MgI}B\xrightarrow{\text{Victor Meyer test}}\text{Blue colour}\]
Appearance of blue colour in Victor Meyer test indicates that $$B$$ is \[{{\text{2}}^{\circ }}\] alcohol and thus $$A$$ must be an aldehyde other than $$HCHO.$$ Thus among the given options, only option (C) is correct.
238.
$$n$$ - Propyl alcohol and $$iso$$ - propyl alcohol can be chemically distinguished by which reagent?
$$n$$ - Propyl alcohol on oxidation with potassium dichromate gives an aldehyde which on further oxidation gives an acid. Both aldehyde and acid contain the same number of $$C$$ atoms as the original alcohol.
\[C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}OH\xrightarrow[\frac{{{K}_{2}}C{{r}_{2}}{{O}_{7}}}{{{H}_{2}}S{{O}_{4}}}]{{{25}^{\circ }}C}\] \[C{{H}_{3}}C{{H}_{2}}CHO\xrightarrow{\frac{{{K}_{2}}C{{r}_{2}}{{O}_{7}}}{{{H}_{2}}S{{O}_{4}}}}\] \[C{{H}_{3}}C{{H}_{2}}COOH\]
Isopropyl alcohol on oxidation gives a ketone with the same number of $$C$$ atoms as the original alcohol.
\[C{{H}_{3}}\underset{\begin{smallmatrix}
| \\
\,\,\,C{{H}_{3}}
\end{smallmatrix}}{\overset{\begin{smallmatrix}
\,\,\,OH \\
|
\end{smallmatrix}}{\mathop{-CH}}}\,\xrightarrow{\frac{{{K}_{2}}C{{r}_{2}}{{O}_{7}}}{{{H}_{2}}S{{O}_{4}}}}C{{H}_{3}}\overset{\begin{smallmatrix}
O \\
\parallel
\end{smallmatrix}}{\mathop{-C-}}\,C{{H}_{3}}\]
239.
Identify $$X$$ in the following sequence :
\[\underset{\left( X \right)}{\mathop{{{C}_{3}}{{H}_{8}}O}}\,\xrightarrow[{{H}_{2}}S{{O}_{4}}]{{{K}_{2}}C{{r}_{2}}{{O}_{7}}}{{C}_{3}}{{H}_{6}}O\xrightarrow[{{I}_{2}}+NaOH]{\text{warm}}CH{{I}_{3}}\]
Since the compound $$X\left( {{C_3}{H_6}O} \right)$$ gives iodoform test, it must have $$ - COC{H_3}$$ groups hence it should be $$C{H_3}COC{H_3}.$$ Therefore $$X$$ should be $$C{H_3}CH\left( {OH} \right)C{H_3}.$$
240.
Ethylene oxide when treated with Grignard reagent yields