The reactant 'P' in the following reactions is `P underset(dil.H_2SO_4)overset(K_2Cr_2O_7)rarrBunderset(H_3O^+)overset(CH_3MgBr)rarrCH_3-underset(OH)underset(|)overset(CH_3)overset(|)C-CH_3`

Options

A. `CH_3CHOHCH_3`
B. `CH_3COCH_3`
C. `CH_3CH_2OH`
D. `CH_3COOH`

Answer

To determine the reactant 'P' in the given reactions, we need to analyze the steps involved in the transformation of 'P' to the final product. Here’s a step-by-step breakdown of the solution:

### Step 1: Identify the Final Product
The final product is a tertiary alcohol, which has the structure:
\[ CH_3 - C(OH)(CH_3) - CH_3 \]
This indicates that the product must have three methyl groups (CH₃) attached to the carbon bearing the hydroxyl group (OH).

### Step 2: Understand the Role of Grignard Reagent
The Grignard reagent used here is \( CH_3MgBr \). When it reacts with a carbonyl compound (aldehyde or ketone), it adds to the carbonyl carbon, leading to the formation of a tertiary alcohol if the carbonyl compound is a ketone.

### Step 3: Determine the Structure of Intermediate B
Since the final product is a tertiary alcohol, the intermediate 'B' must be a ketone that has two methyl groups (CH₃) attached to the carbonyl carbon. Thus, 'B' can be identified as:
\[ CH_3 - C(=O) - CH_3 \]
This is known as acetone or propanone.

### Step 4: Identify Reactant P
Now, we need to find a compound 'P' that, when oxidized, yields the ketone 'B'. The oxidation of 'P' must produce a compound with two methyl groups that can be converted into the ketone structure.

### Step 5: Analyze Possible Structures for P
To find 'P', we can consider the following options:
1. A secondary alcohol that can be oxidized to a ketone.
2. A compound that, upon oxidation, will yield two methyl groups on the carbonyl carbon.

### Step 6: Evaluate Each Option
We will evaluate each compound given in the options to see which one can be oxidized to yield the ketone 'B':
- **Option 1:** A secondary alcohol with two methyl groups would yield the required ketone upon oxidation.
- **Option 2:** A compound with a carbonyl group (like an aldehyde) would not yield a ketone upon oxidation.
- **Option 3:** An alcohol that can be oxidized to a ketone.
- **Option 4:** A compound that would yield a carboxylic acid upon oxidation.

### Step 7: Conclusion
After evaluating the options, the correct reactant 'P' must be a secondary alcohol that, upon oxidation, gives the ketone (propanone). Thus, the structure of 'P' is likely:
\[ CH_3 - CH(OH) - CH_3 \]
This structure has two methyl groups and can be oxidized to yield the ketone 'B'.

### Final Answer
The reactant 'P' is:
\[ CH_3 - CH(OH) - CH_3 \] (2-propanol)