Cyclohexyl Bromide

Definition

Cyclohexyl bromide is an organic compound consisting of a cyclohexane ring with a bromine atom attached. It is an important intermediate in organic synthesis and is relevant in the context of the E2 reaction and the deuterium isotope effect.

5 Must Know Facts For Your Next Test

1. Cyclohexyl bromide is a primary alkyl halide, meaning the bromine atom is attached to a primary carbon.
2. The cyclohexane ring in cyclohexyl bromide can adopt either an equatorial or axial orientation of the bromine substituent.
3. Cyclohexyl bromide undergoes an E2 elimination reaction when treated with a strong base, resulting in the formation of cyclohexene.
4. The deuterium isotope effect can be observed in the E2 elimination of cyclohexyl bromide, where the reaction rate is slower when the hydrogen atom is replaced with deuterium.
5. The stereochemistry of the E2 elimination of cyclohexyl bromide is anti-periplanar, with the base and the leaving group positioned on opposite sides of the carbon-carbon bond being broken.

Review Questions

• Explain how the structure of cyclohexyl bromide influences its reactivity in an E2 elimination reaction.
  • The cyclohexane ring in cyclohexyl bromide can adopt either an equatorial or axial orientation of the bromine substituent. The equatorial orientation is more stable and preferred, as it minimizes steric interactions. In the E2 elimination, the base attacks the carbon bearing the bromine atom, and the bromine is eliminated as a leaving group. The anti-periplanar arrangement of the base and the leaving group is required for the E2 mechanism, which is facilitated by the equatorial orientation of the bromine in cyclohexyl bromide.
• Describe the deuterium isotope effect observed in the E2 elimination of cyclohexyl bromide.
  • The deuterium isotope effect refers to the difference in reaction rate when a hydrogen atom is replaced with a deuterium atom. In the E2 elimination of cyclohexyl bromide, the rate of the reaction is slower when the hydrogen atom is replaced with deuterium. This is because the carbon-deuterium bond is stronger than the carbon-hydrogen bond, making it more difficult for the base to abstract the deuterium atom. The slower rate of the reaction with deuterium is an example of the primary deuterium isotope effect, which provides insights into the mechanism and transition state of the E2 elimination.
• Evaluate the significance of the cyclohexyl bromide structure and reactivity in the context of organic synthesis.
  • Cyclohexyl bromide is an important intermediate in organic synthesis due to its versatile reactivity. The cyclohexane ring provides a stable framework, and the bromine substituent can undergo various transformations, such as nucleophilic substitution, elimination, and metal-halogen exchange reactions. The ability to control the orientation of the bromine atom (equatorial or axial) allows for the selective formation of different products, which is crucial in the synthesis of complex organic molecules. Furthermore, the deuterium isotope effect observed in the E2 elimination of cyclohexyl bromide can be utilized to probe the reaction mechanism and guide the design of synthetic strategies.

Related terms

Cyclohexane:

A saturated alicyclic hydrocarbon with the molecular formula C₆H₁₂. It has a stable chair conformation and is a common building block in organic chemistry.

Bromine:

A dense, dark-red, corrosive liquid element that is a member of the halogen group. It is commonly used as a leaving group in organic reactions.

E2 Reaction:

A bimolecular elimination reaction where a base removes a hydrogen atom and a leaving group simultaneously, resulting in the formation of an alkene.