A : Two moles of Grignard reagent is consumed in the formation of tertiary alcohol from ester following by hydrolysis .
R : One mole of Grignard reagent convert ester into Ketone and second mole of Grignard reagent adds to Ketone .

Options

A. Both Assertion & Reason are true and the reason is the correct explanation of the assertion
B. Both Assertion & Reason are true but the reason is not the correct explanation of the assertion
C. Assertion is true statement but Reason is false
D. Both Assertion and Reason are false statements

Answer

To solve the problem, we need to analyze the assertion (A) and reason (R) statements regarding the reaction of Grignard reagents with esters to form tertiary alcohols.

### Step-by-Step Solution:

1. **Understanding the Reaction**:
- The reaction involves an ester (R-C(=O)-O-R') reacting with a Grignard reagent (R''-MgX).

2. **First Mole of Grignard Reagent**:
- The first mole of Grignard reagent attacks the carbonyl carbon of the ester. This results in the formation of a tetrahedral intermediate.
- The reaction can be represented as:
\[ R-C(=O)-O-R' + R''-MgX \rightarrow R-C(OH)(O-R')-R'' \]

3. **Hydrolysis of the Intermediate**:
- Upon hydrolysis (addition of water and an acid), the tetrahedral intermediate collapses, leading to the formation of a ketone and an alcohol:
\[ R-C(OH)(O-R')-R'' \xrightarrow{H^+/H_2O} R-C(=O)-R' + R''-OH \]

4. **Second Mole of Grignard Reagent**:
- The ketone (R-C(=O)-R') formed from the first reaction can now react with another mole of Grignard reagent (R''-MgX).
- This second mole attacks the carbonyl carbon of the ketone:
\[ R-C(=O)-R' + R''-MgX \rightarrow R-C(OH)(O-R')-R'' \]

5. **Final Hydrolysis**:
- The resulting tetrahedral intermediate from the second reaction is again hydrolyzed to yield the final product, which is a tertiary alcohol:
\[ R-C(OH)(O-R')-R'' \xrightarrow{H^+/H_2O} R-C(OH)-R'-R'' \]

6. **Conclusion**:
- Thus, two moles of Grignard reagent are indeed consumed in the formation of a tertiary alcohol from an ester, confirming the assertion (A) is true.
- The reason (R) correctly explains the assertion, as the first mole converts the ester to a ketone, and the second mole adds to the ketone to form the tertiary alcohol.

### Final Answer:
Both assertion and reason are true, and the reason is the correct explanation of the assertion.