What is the chemical equation involved with the reaction of cyclohexene with Br2?
The correct answer and explanation is:
The reaction of cyclohexene with bromine (Br₂) is an example of an electrophilic addition reaction. When cyclohexene reacts with Br₂, the double bond in cyclohexene undergoes a reaction with bromine, resulting in the formation of a vicinal dibromide (a compound with two bromine atoms attached to adjacent carbon atoms in the cyclohexane ring). The general chemical equation for this reaction is:
C₆H₁₀ + Br₂ → C₆H₁₀Br₂
Explanation:
- Reaction Mechanism:
- Cyclohexene (C₆H₁₀) has a carbon-carbon double bond (C=C). Bromine (Br₂), which is a non-polar molecule, approaches the double bond.
- The double bond in cyclohexene is electron-rich and acts as a nucleophile, attracting the electrophilic bromine molecule.
- The Br₂ molecule becomes polarized as the electron-rich π-bond in cyclohexene induces a dipole in the Br₂ molecule, leading to the formation of a bromonium ion intermediate.
- Bromonium Ion Formation:
- The bromonium ion is a three-membered ring with a positively charged bromine atom attached to the two carbon atoms of the former double bond.
- This intermediate is highly unstable and electrophilic.
- Attack by Bromide Ion (Br⁻):
- The bromonium ion is then attacked by a bromide ion (Br⁻), which is formed when Br₂ dissociates. The attack can occur at either of the two carbon atoms involved in the bromonium ion.
- This attack results in the opening of the three-membered ring and the formation of a vicinal dibromide (two bromine atoms attached to adjacent carbon atoms).
- Final Product:
- The final product is 1,2-dibromocyclohexane, where two bromine atoms are added to the carbon atoms that were originally part of the double bond in cyclohexene.
Important Points:
- The reaction is stereospecific, meaning that the addition of bromine occurs in a specific manner, often leading to anti addition, where the two bromine atoms are added on opposite sides of the cyclohexane ring.
- This type of addition reaction is typical of alkenes and is driven by the formation of a stable bromonium ion intermediate.
The overall reaction is a classic example of electrophilic addition, which is an essential reaction mechanism in organic chemistry.