Test: Electrophilic Substitution Reactions - NEET MCQ

The correct answer is Option B.
Fluorination (155 kJ/mol) seems to have relatively high activation energy. The initial reaction (chain initiation) - that is, the homolytic cleavage of a halogen molecule - must, however, occur only a few times. 
The subsequent reactions (chain propagation) between a halogen radical and methane, and then between a methyl radical and a halogen molecule, yield another halogen radical. 
Therefore, one start reaction may initiate thousands of fluorination reactions. In addition, fluorination is very exothermic, the reaction enthalpy is −431 kJ/mol. As a result, the reaction itself provides enough energy for additional initiation reactions.
Hence, the halogenation of alkanes is violent and very fast in Fluorine.
So the correct option is B.
 

The correct answer is option A
Electron donating group (EDG) increases the reactivity of electrophilic substitution reaction and electron withdrawing group (EWG) decreases it.

THE HALOGENATION OF BENZENE
This page gives you the facts and a simple, uncluttered mechanism for the electrophilic substitution reaction between benzene and chlorine or bromine in the presence of a catalyst such as aluminium chloride or iron.

The function of AlCl₃ in Friedel-Crafts reaction, is to produce electrophile which later attack on benzene.

The correct answer is option D
The function of AlCl3​, in Friedel-Craft reaction, is to produce electrophile, which later adds to the benzene nucleus. This electrophilic aromatic substitution allows the synthesis of monoacetylated products from the reaction between arenes and acyl chlorides or anhydrides. The products are deactivated and do not undergo a second substitution. Normally, a stoichiometric amount of the Lewis acid catalyst is required for both the substrate and the product form complexes.
AlCl3​ (and other Lewis acids like it) will coordinate to halogens, and facilitate the breaking of these bonds.  In doing so, it increases the electrophilicity of its binding partner, making it much more reactive.

The correct answer is Option D.
Due to the +I effect of CH3 in toluene, it is more reactive than benzene. Due to electron withdrawing nature of −COOH group in benzoic acid and −NO2 group in nitrobenzene, both benzoic acid and nitrobenzene are less reactive than benzene.

The correct answer is Option C.
Benzene can be converted into ethyl benzene as follows.
Step-1:—Conversion of benzene into 
Benzene is treated with acetyl chloride in presence of anhydrous AlCl₃ to form acetophenone (phenyl ethanone).This is electrophilic substitution reaction.

Step-2:—Reduction of acetophenone into ethyl benzene.
Acetophenone is treated with hydrazine to form acetophenone hydrazone,which on heating in presence of high boiling solvent like ethylene glycol gives ethyl benzene.This reaction is known as Wolff-Kishner reduction.

 

From the given example, Toluene is the compound that is more reactive towards electrophilic Nitration. Toluene has a CH3 group on benzene ring and due to plus hyperconjugation it activates the presence of electrons inside the ring. Why nitrobenzene and benzoic acid have - M effect,they will draw electron cloud from the benzene ring and have deactivated the benzene ring from electrophilic Nitration.