What is product of the following sequence of reactions ?
`(CH_(3))_(2)C=CHCH_(2)CH_(3)overset((i)BH_(3)//THF)underset((ii)H_(2)O_(2),OH^(-))rarr overset("PCC")underset(CH_(2)Cl_(2))rarr overset((i)CH_(3)MgBr)underset((ii)H_(3)O^(+))rarr`

Options

A. 2, 4 - dimethyl - 3- pentanol
B. 2, 3 - dimethyl - 3- pentanol
C. 2, 3 - dimethyl - 2- pentanol
D. 2, 2 - dimethyl - 3 - pentanol

Explanation

To determine the product of the given sequence of reactions, we will break down each step systematically.

### Step 1: Hydroboration-Oxidation
The starting compound is `(CH₃)₂C=CHCH₂CH₃`, which is an alkene. We will first perform hydroboration using BH₃ in THF followed by oxidation with H₂O₂ and OH⁻.

1. **Hydroboration**: The alkene reacts with BH₃, leading to the formation of an organoborane intermediate. According to the anti-Markovnikov rule, the boron atom will attach to the less substituted carbon (the one with fewer hydrogens), and the hydrogen will add to the more substituted carbon.
- The product of this step will be: `(CH₃)₂C(OH)CH₂CH₃` (an alcohol).

2. **Oxidation**: The organoborane intermediate is then oxidized with H₂O₂ in the presence of OH⁻, replacing the boron with a hydroxyl group.
- The final product after this step is: `(CH₃)₂C(OH)CH₂CH₃`.

### Step 2: Oxidation with PCC
The alcohol obtained from the previous step is now treated with PCC (Pyridinium Chlorochromate) in CH₂Cl₂, which is a mild oxidizing agent.

1. **Oxidation of Alcohol to Ketone**: The alcohol will be oxidized to a ketone by removing two hydrogen atoms and adding an oxygen atom.
- The product after this step will be: `(CH₃)₂C=OCH₂CH₃` (a ketone).

### Step 3: Reaction with Grignard Reagent
Next, we will react the ketone with a Grignard reagent, `CH₃MgBr`, followed by hydrolysis with `H₃O⁺`.

1. **Nucleophilic Attack**: The Grignard reagent acts as a nucleophile and attacks the electrophilic carbonyl carbon of the ketone. This forms a tetrahedral intermediate.
- The intermediate will be: `CH₃C(OH)(CH₃)CH₂CH₃`.

2. **Hydrolysis**: The intermediate is then hydrolyzed with `H₃O⁺`, which will protonate the alkoxide to form the final alcohol.
- The final product after hydrolysis will be: `CH₃C(OH)(CH₃)CH₂CH₃`.

### Final Product
The final product of the entire reaction sequence is:
**2,3-dimethyl-3-pentanol**.

### Summary of Steps
1. Hydroboration-Oxidation of alkene to form an alcohol.
2. Oxidation of the alcohol to a ketone using PCC.
3. Nucleophilic attack by Grignard reagent followed by hydrolysis to form the final alcohol.