Hyperconjugation in 2,3-dimethyl-2-butene:

Introduction:
Hyperconjugation is a stabilizing interaction between an empty or partially filled p orbital and adjacent σ or π bonds. It occurs due to the delocalization of electrons through the σ or π system, resulting in the stabilization of the molecule. In 2,3-dimethyl-2-butene, hyperconjugation plays a significant role in determining the stability and reactivity of the molecule.

Structure of 2,3-dimethyl-2-butene:
2,3-dimethyl-2-butene is a hydrocarbon with the molecular formula C7H14. It contains a double bond between the second and third carbon atoms, and two methyl groups attached to the second carbon atom.

Hyperconjugated Structures:
Hyperconjugation can occur between the π bond and the adjacent σ bonds involving the carbon atoms bonded to the double bond. In 2,3-dimethyl-2-butene, there are two adjacent σ bonds that can participate in hyperconjugation: the C2-C3 σ bond and the C2-C1 σ bond.

Hyperconjugation with C2-C3 σ bond:
When the π bond is delocalized with the C2-C3 σ bond, the following hyperconjugated structures can be formed:

1. Structure 1: In this structure, one of the methyl groups is in the anti-periplanar position with respect to the C2-C3 σ bond. The π electrons are delocalized towards the antibonding orbital of the C2-C3 σ bond, resulting in stabilization.

2. Structure 2: In this structure, the other methyl group is in the anti-periplanar position with respect to the C2-C3 σ bond. The π electrons are delocalized towards the antibonding orbital of the C2-C3 σ bond, leading to stabilization.

Hyperconjugation with C2-C1 σ bond:
When the π bond is delocalized with the C2-C1 σ bond, the following hyperconjugated structures can be formed:

3. Structure 3: In this structure, one of the methyl groups is in the anti-periplanar position with respect to the C2-C1 σ bond. The π electrons are delocalized towards the antibonding orbital of the C2-C1 σ bond, resulting in stabilization.

4. Structure 4: In this structure, the other methyl group is in the anti-periplanar position with respect to the C2-C1 σ bond. The π electrons are delocalized towards the antibonding orbital of the C2-C1 σ bond, leading to stabilization.

Total number of hyperconjugated structures:
By considering all possible combinations of hyperconjugation with the C2-C3 σ bond and the C2-C1 σ bond, we can determine the total number of hyperconjugated structures for 2,3-dimethyl-2-butene. In this case, there are two possibilities for each σ bond, resulting in a total of four hyperconjugated structures.

Conclusion:
In summary, 2,3-dimethyl-2-butene can have four hyperconjugated structures.