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Consider the conversion of chlorobenzene to phenol. What are the typical conditions required for this reaction?
The NCERT mentions, 'Chlorobenzene can be converted into phenol by heating in aqueous sodium hydroxide solution at a temperature of 623K and a pressure of 300 atmospheres.'
Which of the following electrophilic substitution reactions is NOT mentioned as being undergone by haloarenes?
The NCERT lists, 'Haloarenes undergo the usual electrophilic reactions of the benzene ring such as halogenation, nitration, sulphonation and Friedel-Crafts reactions.' Wurtz reaction involves coupling of alkyl halides and is not an electrophilic substitution of the benzene ring.
In the resonance structures of halobenzene, where is the electron density increased the most?
According to the NCERT, 'Due to resonance, the electron density increases more at ortho- and para-positions than at meta-positions.'
Why is the $\text{SN}_1$ mechanism ruled out for nucleophilic substitution reactions in haloarenes?
The NCERT states, 'Instability of phenyl cation: In case of haloarenes, the phenyl cation formed as a result of self-ionisation will not be stabilised by resonance and therefore, SN1 mechanism is ruled out.'
Compared to benzene, electrophilic substitution reactions in haloarenes occur:
The NCERT says, 'As a result, the ring gets somewhat deactivated as compared to benzene and hence the electrophilic substitution reactions in haloarenes occur slowly and require more drastic conditions as compared to those in benzene.'
Which of the following is responsible for the deactivating nature of a halogen atom in electrophilic substitution reactions of haloarenes?
The NCERT notes, 'Further , the halogen atom because of its –I effect has some tendency to withdraw electrons from the benzene ring. As a result, the ring gets somewhat deactivated as compared to benzene...'
If a nitro group is present at the meta-position in a haloarene, what is its expected influence on the reactivity towards nucleophilic substitution reactions?
The NCERT states, 'However, no effect on reactivity of haloarenes is observed by the presence of electron withdrawing group at meta-position. ...Therefore, the presence of nitro group at meta- position does not stabilise the negative charge and no effect on reactivity is observed by the presence of –NO2 group at meta-position.'
Why is it less likely for an electron-rich nucleophile to approach electron-rich arenes?
One of the reasons given in NCERT for less reactivity towards nucleophilic substitution is, 'Because of the possible repulsion, it is less likely for the electron rich nucleophile to approach electron rich arenes.'
What kind of hybridization does the carbon atom attached to the halogen have in a haloarene?
The NCERT states, 'Haloarenes contain halogen atom(s) attached to sp2 hybridised carbon atom(s) of an aryl group.' Also, 'In haloalkane, the carbon atom attached to halogen is sp3 hybridised while in case of haloarene, the carbon atom attached to halogen is sp 2-hybridised.'
Which of the following vitamins is primarily stored in the liver and adipose tissues?
According to the NCERT text, 'Vitamins which are soluble in fat and oils but insoluble in water are kept in this group. These are vitamins A, D, E and K. They are stored in liver and adipose (fat storing) tissues.' Vitamin A is a fat-soluble vitamin.
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