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NEET CHEMISTRYMedium

The reaction of toluene with Cl2Cl_2 in presence of FeCl3FeCl_3 gives ‘X' and the reaction in presence of light gives 'Y'. 'X' and 'Y' are respectively:

A

X= Benzal chloride, Y= o-chlorotoluene

B

X= m-chlorotoluene, Y= p-chlorotoluene

C

X= o and p-chlorotoluene, Y= trichloromethyl benzene

D

X= Benzyl chloride, Y= m-chlorotoluene

Step-by-Step Solution

  1. Reaction producing X (Electrophilic Aromatic Substitution): When toluene reacts with chlorine (Cl2Cl_2) in the presence of a Lewis acid catalyst like iron(III) chloride (FeCl3FeCl_3) or iron (FeFe), an electrophilic substitution reaction occurs on the benzene ring. The methyl group (CH3-CH_3) is an ortho-para directing group. Therefore, the entering chlorine atom attacks the ortho and para positions relative to the methyl group, yielding a mixture of o-chlorotoluene and p-chlorotoluene . C6H5CH3+Cl2FeCl3oClC6H4CH3+pClC6H4CH3C_6H_5CH_3 + Cl_2 \xrightarrow{FeCl_3} o-ClC_6H_4CH_3 + p-ClC_6H_4CH_3

  2. Reaction producing Y (Free Radical Substitution): When the reaction is carried out in the presence of light (hνh\nu) or heat, the conditions favour a free radical mechanism. This leads to substitution in the alkyl side chain (benzylic position) rather than the ring, similar to the halogenation of alkanes . The hydrogen atoms of the methyl group are replaced by chlorine atoms. Depending on the extent of reaction, mono-, di-, or tri-chlorinated products (benzyl chloride, benzal chloride, or benzotrichloride) are formed. Option 3 specifies trichloromethyl benzene (benzotrichloride), which is the product of exhaustive side-chain chlorination. C6H5CH3+3Cl2hνC6H5CCl3+3HClC_6H_5CH_3 + 3Cl_2 \xrightarrow{h\nu} C_6H_5CCl_3 + 3HCl

  3. Conclusion: X is the mixture of ring-substituted isomers (o and p-chlorotoluene), and Y is the side-chain substituted product (trichloromethyl benzene).

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