Methyl benzene is electron releasing group so that an electrophile can be substituted by replacing the hydrogen atom in the benzene. Methyl group is more electron releasing group than ethyl because the carbon atom which attaches directly to benzene by hyperconjugation has 3 alpha hydrogen atoms whereas carbon of ethyl group has 2 alpha hydrogen atoms

Introduction:
Electrophilic aromatic substitution (EAS) is a reaction in which an electrophile replaces a hydrogen atom in an aromatic compound. The reactivity of different aromatic compounds towards EAS can vary depending on the presence of electron-donating or electron-withdrawing groups. In this case, we will consider four aromatic compounds: methyl benzene, ethyl benzene, nitro benzene, and chloro benzene, and evaluate their reactivity towards EAS.

Reactivity of Aromatic Compounds:

1. Methyl Benzene:
Methyl benzene, also known as toluene, has a methyl group (-CH3) attached to the benzene ring. The methyl group is weakly electron-donating, which increases the electron density on the ring. This electron donation makes the benzene ring more nucleophilic, enhancing its reactivity towards electrophiles. Therefore, methyl benzene is relatively more reactive towards EAS compared to benzene.

2. Ethyl Benzene:
Ethyl benzene has an ethyl group (-CH2CH3) attached to the benzene ring. The ethyl group is also weakly electron-donating, similar to the methyl group in toluene. As a result, ethyl benzene exhibits similar reactivity towards EAS as methyl benzene. The presence of the ethyl group enhances the nucleophilicity of the benzene ring, making it more reactive towards electrophiles.

3. Nitro Benzene:
Nitro benzene contains a nitro group (-NO2) attached to the benzene ring. The nitro group is a strong electron-withdrawing group due to the presence of the electronegative nitrogen and oxygen atoms. This electron-withdrawing nature decreases the electron density on the benzene ring, making it less nucleophilic. Consequently, nitro benzene is less reactive towards EAS compared to benzene, methyl benzene, and ethyl benzene.

4. Chloro Benzene:
Chloro benzene has a chlorine atom (-Cl) attached to the benzene ring. Chlorine is a weakly electron-withdrawing group and has a slightly deactivating effect on the benzene ring. While the chlorine atom withdraws some electron density from the ring, it is not as strong as the nitro group in nitro benzene. Therefore, chloro benzene is less reactive towards EAS compared to benzene but more reactive than nitro benzene.

Conclusion:
In summary, among the given aromatic compounds, methyl benzene and ethyl benzene are the most reactive towards electrophilic aromatic substitution due to the presence of weakly electron-donating groups. Nitro benzene is the least reactive due to the strong electron-withdrawing nature of the nitro group. Chloro benzene is moderately reactive, with a slightly lower reactivity compared to methyl benzene and ethyl benzene.