Final answer:
In the case of a large alkyl group attached to an aromatic ring, steric hindrance makes the para position more favorable for future substitution. The numbering of substituents on a benzene ring goes by the lowest possible numbers with the first alphabetically being number 1. Electron donating groups direct EAS to the ortho and para positions, but steric hindrance from large groups favors the para position.
Step-by-step explanation:
If the alkyl group substituent on the aromatic ring is large, it will influence the positioning of further substitutions due to steric hindrance. In electrophilic aromatic substitution (EAS) reactions, large alkyl groups like tert-butyl can limit the accessibility to the ortho and meta positions on the benzene ring due to their size. Hence, the para position is generally more favorable for future substitutions as it is the farthest from the alkyl group, offering the least steric hindrance. This is because the larger the substituent, the more it interferes with the approach of electrophiles to the ortho and meta positions.
During the numbering of the benzene ring with multiple substituents, the substituent that is first alphabetically gets the number 1 position, and the numbering proceeds to give the lowest possible numbers to the other substituents. Electron donating groups, which include alkyl groups, generally direct future substituents to the ortho and para positions. However, due to the size of the large alkyl group, the para position becomes the preferred location for future substitution.
Nucleophilic aromatic substitution is a different type of reaction that is influenced by the presence of electron withdrawing groups, such as a nitro group or carbonyl groups, which can make the ring more susceptible to attack by nucleophiles.