Bromination of Benzene: Identifying the Major Product

The question asks to identify the major product formed during the bromination of benzene.

Bromination of benzene is a classic example of an electrophilic aromatic substitution reaction. Benzene is an aromatic compound, and it undergoes substitution reactions rather than addition reactions because substitution preserves the stable aromatic ring structure.

The reaction involves benzene ($\text{C}_6\text{H}_6$) reacting with bromine ($\text{Br}_2$) in the presence of a Lewis acid catalyst, such as iron(III) bromide ($\text{FeBr}_3$) or aluminum bromide ($\text{AlBr}_3$). The catalyst helps to polarize the bromine molecule and generate the electrophile.

The mechanism involves the following key steps:

1. Generation of the electrophile: The Lewis acid catalyst reacts with bromine to form a strongly electrophilic species, typically represented as $\text{Br}^+$.
   $\text{Br}_2 + \text{FeBr}_3 \rightarrow \text{Br}^+ + \text{FeBr}_4^-$
2. Electrophilic attack: The $\text{Br}^+$ electrophile attacks the electron-rich benzene ring, disrupting the aromaticity temporarily and forming a sigma complex (also known as an arenium ion or Wheland intermediate).
3. Deprotonation: A base (such as the $\text{FeBr}_4^-$ ion) removes a proton ($\text{H}^+$) from the sigma complex, restoring the aromaticity of the ring and forming the substituted product, bromobenzene.
   $\text{Sigma Complex} + \text{FeBr}_4^- \rightarrow \text{Bromobenzene} + \text{HBr} + \text{FeBr}_3$

The overall reaction is:

$\text{C}_6\text{H}_6 + \text{Br}_2 \xrightarrow{\text{FeBr}_3} \text{C}_6\text{H}_5\text{Br} + \text{HBr}$

Where $\text{C}_6\text{H}_5\text{Br}$ represents bromobenzene.

Let's look at the given options:

• Hydrogen bromide ($\text{HBr}$): This is a byproduct of the reaction, not the major organic product.
• Bromobenzene: This is the main organic compound formed when one hydrogen atom on the benzene ring is replaced by a bromine atom.
• Cyclobromobenzene: This is not a standard chemical name. "Bromobenzene" is the correct and standard name for the compound formed.
• Cyclobromopentane: This is a five-membered cyclic alkane with a bromine substituent. It is completely different from benzene and its reaction products.

Therefore, the major product formed in the bromination of benzene is bromobenzene.