Correct option is D
Aluminium chloride, also known as aluminium trichloride, is an inorganic compound with the formula AlCl3.Anhydrous aluminium chloride is a powerful Lewis acid. Carbonyl carbon will become more electron deficient due to chelation of the oxygen atom with AlCl3.
A six membered ring will be formed and a two degree carbocation will be generated. Cl- will attack the secondary carbocation.
A five membered ring will not be formed as it will lead to generation of a primary carbocation.
Information Booster
Hyperconjugation (σ-conjugation or no-bond resonance) refers to the delocalization of electrons with the participation of bonds of primarily σ-character. Usually, hyperconjugation involves the interaction of the electrons in a sigma (σ) orbital (e.g. C–H or C–C) with an adjacent unpopulated non-bonding p or antibonding σ* or π* orbitals to give a pair of extended molecular orbitals.
Stability of carbocations:
The three C–H σ bonds of the methyl group(s) attached to the carbocation can undergo the stabilization interaction but only one of them can be aligned perfectly with the empty p-orbital, depending on the conformation of the carbon–carbon bond. Donation from the two misaligned C–H bonds is weaker. The more adjacent methyl groups there are, the larger hyperconjugation stabilization is because of the increased number of adjacent C–H bonds.
