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प्रश्न
Explain why Lewis acid is not required in bromination of phenol?
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उत्तर
Usual halogenation is carried out in the presence of Lewis acid, \[\ce{FeBr3}\] which polarises the halogen molecule. In case of phenol, the polarisation of bromine occurs even in the absence of Lewis acid. This is because of highly activating effect of –OH group on the benzene ring. The reaction follows:
Note: In aqueous solution, phenol ionizes to give phenoxide ion. Due to the presence of the negative charge, the oxygen atom of the phenoxide ion donates electrons to the benzene ring to a large extent. As a result, the ring gets highly activated leading to the formation of trisubstituted product. On the other hand, in the non-polar solvents, the ionization of phenol does not occurs to a large extent. As a result, the -OH group donates electrons to the benzene ring only to a small extent. Consequently, the ring is activated slightly and, therefore, only monosubstitution occurs.
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संबंधित प्रश्न
Name the following compound according to the IUPAC system.
\[\begin{array}{cc}
\phantom{..................}\ce{CH2OH}\\
\phantom{.........}|\\
\ce{CH3 - CH2 - CH - CH - CH - CH3}\\
\phantom{.........}|\phantom{...................}|\\
\phantom{.............}\ce{CH2Cl}\phantom{..........}\ce{CH3}\phantom{}
\end{array}\]
Name the following compound according to the IUPAC system.
\[\begin{array}{cc}
\phantom{.....................................}\ce{CH2OH}\\
\phantom{............................}|\\
\ce{CH3 - CH - CH2 - CH - CH - CH3}\\
|\phantom{....................}|\phantom{............}\\
\ce{CH3}\phantom{..............}\ce{OH}\phantom{.........}\\
\end{array}\]
Name the following compound according to the IUPAC system.
\[\begin{array}{cc}
\ce{H2C = CH - CH - CH2 - CH2 - CH3}\\
|\phantom{...............}\\
\ce{OH}\phantom{............}
\end{array}\]
Give the IUPAC name of the following ether:
CH3CH2CH2OCH3
Natalite is a mixture of
(a) diethyl ether and methanol
(b) diethyl ether and ethanol
(c) dimethyl ether and methanol
(d) dimethyl ether and ethanol
How is phenol converted into the following?
Benzene
How is phenol converted into the following?
benzoquinone
Write the IUPAC name of the following compound:
Resorcinol on distillation with zinc dust gives _________.
Write structural formulae for 3-Methoxyhexane
Give IUPAC names of the following compound:
C6H5OCH2CH3 is called:
Ethylene reacts with Baeyer’s reagent to give ______.
The heating of phenyl methyl ether with HI produces:
\[\ce{Phenol ->[Zn, dust] 'X' ->[CH3Cl][Anhy. AlCl3] 'Y' ->[Alkaline][KMnO4] 'Z'}\]
The product ‘Z’ is:
Which of the following compounds will react with sodium hydroxide solution in water?
Identify A and B in the following:
Write the IUPAC name.
\[\begin{array}{cc}
\phantom{................}\ce{CH3}\\
\phantom{.............}|\\
\ce{CH3 - CH - CH - C -CH3}\\
\phantom{.}|\phantom{......}|\phantom{......}|\\
\phantom{....}\ce{CH3\phantom{...}\ce{OH}\phantom{...}\ce{CH3}}\
\end{array}\]
