The frontier orbital interactions involved in the formation of Carbocation intermediate in the reaction of isobutylene with HCl are -

Concept:

• Frontier Orbital Theory: This theory explains chemical reactivity in terms of interactions between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of interacting molecules.

  • HOMO (Highest Occupied Molecular Orbital): For isobutylene (an alkene), the HOMO is the π orbital.

  • LUMO (Lowest Unoccupied Molecular Orbital): For HCl, the LUMO is typically the σ* (antibonding) orbital.

• Formation of Carbocation: In the reaction of isobutylene (an olefin) with HCl, an electrophilic addition occurs.

  • The π (HOMO) of isobutylene interacts with the σ* (LUMO) of HCl, leading to the formation of a carbocation intermediate.

Explanation:

π of olefin and σ* of HCl:

• This is the correct interaction as the π (HOMO) of the olefin donates electrons to the σ* (LUMO) of HCl, facilitating the formation of a carbocation intermediate.

Conclusion:

The correct frontier orbital interactions involved in the formation of a carbocation intermediate in the reaction of isobutylene with HCl are: π of olefin and σ* of HCl