Does m-xylene or p-xylene react more rapidly with Cl2 + FeCl3? Explain your answer.

Verified step by step guidance

1. Identify the structures of m-xylene and p-xylene. m-Xylene has methyl groups at the 1 and 3 positions, while p-xylene has them at the 1 and 4 positions.
2. Understand the role of Cl2 + FeCl3. This is a chlorination reaction, specifically an electrophilic aromatic substitution (EAS) where Cl2 acts as the electrophile.
3. Consider the directing effects of the methyl groups. Methyl groups are electron-donating and activate the benzene ring towards EAS, directing incoming electrophiles to ortho and para positions.
4. Analyze the steric and electronic effects. In m-xylene, the ortho positions are less accessible due to steric hindrance from the adjacent methyl group, while in p-xylene, the para position is more accessible and less hindered.
5. Conclude which xylene is more reactive. p-Xylene is more reactive because the para position is more accessible and less hindered, allowing for a faster reaction with Cl2 + FeCl3.

Key Concepts

Electrophilic Aromatic Substitution

Electrophilic aromatic substitution (EAS) is a fundamental reaction mechanism in organic chemistry where an electrophile replaces a hydrogen atom on an aromatic ring. The presence of substituents on the ring can influence the reactivity and orientation of the substitution. In the case of xylene isomers, the position of the methyl groups affects how readily the ring can react with electrophiles like Cl2 in the presence of a catalyst such as FeCl3.

Activating and Deactivating Groups

Substituents on an aromatic ring can be classified as activating or deactivating groups based on their electronic effects. Activating groups, such as methyl groups, increase the electron density of the ring, making it more reactive towards electrophiles. In contrast, deactivating groups withdraw electron density, reducing reactivity. The position of these groups (ortho, meta, para) also plays a crucial role in determining the rate of reaction with electrophiles.

Steric Hindrance

Steric hindrance refers to the repulsion between atoms that occurs when they are brought close together, which can affect the reactivity of molecules. In the case of m-xylene and p-xylene, the arrangement of the methyl groups can create steric effects that influence how easily the electrophile can approach and react with the aromatic ring. This can lead to differences in reaction rates between the two isomers when reacting with Cl2 and FeCl3.