The reaction,RCOOR'+R''OH (excess) `overset(H^(+)or OH^(-))to` RCOOR''+R'OH is called

Options

A. Esterification
B. Trans-esterification
C. Saponification
D. Hydrolysis

Explanation

To solve the question regarding the reaction \( RCOOR' + R''OH \) (excess) in the presence of \( H^+ \) or \( OH^- \) leading to \( RCOOR'' + R'OH \), we will analyze the components and the type of reaction that occurs.

### Step-by-Step Solution:

1. **Identify the Reactants**:
- The first reactant is \( RCOOR' \), which is an ester.
- The second reactant is \( R''OH \), which is an alcohol.

**Hint**: Recognize the functional groups involved in the reaction.

2. **Understand the Reaction Conditions**:
- The reaction occurs in the presence of an acid catalyst (\( H^+ \)) or a base (\( OH^- \)). This indicates that the reaction is likely to involve some form of nucleophilic attack or protonation.

**Hint**: Consider how acids and bases can affect the reactivity of esters and alcohols.

3. **Analyze the Product Formation**:
- The product formed is \( RCOOR'' + R'OH \). This indicates that the original ester \( RCOOR' \) has undergone a transformation where the alkoxy group \( R' \) has been replaced by \( R'' \) from the alcohol.

**Hint**: Look for any exchange or substitution processes that might occur between the reactants.

4. **Identify the Type of Reaction**:
- The process described is known as **transesterification**, where one ester is converted into another ester by exchanging the alkoxy groups.

**Hint**: Recall the definition of transesterification and how it differs from other reactions like hydrolysis or saponification.

5. **Conclusion**:
- Therefore, the reaction \( RCOOR' + R''OH \overset{H^+ \text{ or } OH^-}{\rightarrow} RCOOR'' + R'OH \) is called **transesterification**.

### Final Answer:
The reaction is called **transesterification**.