Question

Why is methyl benzene more reactive than benzene?

Answer 1

The corresponding negative or positive charge is transmitted across the carbon chain by the atoms belonging to it when an electron-releasing or electron-withdrawing species is introduced to a chain of atoms (usually a carbon chain). The inductive effect is the formation of a permanent dipole in the molecule as a result of this.

Complete answer:
When a chemical species with the tendency to donate electrons, such as an alkyl group, is introduced to a carbon chain, the charge is relayed through the chain and this effect is called the Positive Inductive Effect or the $+ I$ Effect
Because of the high $+ I$ effect caused by hyperconjugation; the methyl group has electron repulsive properties. As a result, the electron is pushed towards the benzene ring, causing the benzene ring in the toluene molecule to become activated, resulting in a higher density of negative charge than in a simple benzene molecule. The toluene molecule is thus vulnerable to electrophilic attack.
Hence, we can say that methyl benzene is more reactive than benzene due to $+ I$ effect of methyl group.

Note:
According to the inductive effect, the charge on a given atom and the charge on a group linked to the atom play a significant role in determining the stability of the resulting molecule. When a group that exhibits the $- I$ effect is linked to a positively charged atom, the positive charge on the resulting molecule is magnified, lowering the molecule's stability.