Mixed ether will not be formed in the reaction-

Options

A. `CH_3OCH_2Cl+C_2H_5MgBr`
B. `CH_2N_2+C_2H_5OH`
C. `C_2H_5ONa+CH_3I`
D. `C_2H_5OH+H_2SO_4(140^@C)`

Answer

To determine which reaction does not yield a mixed ether, we need to analyze the options provided. A mixed ether is formed when two different alkyl groups are bonded to the same oxygen atom in the ether structure (ROR').

### Step-by-Step Solution:

1. **Understanding Ether Formation:**
- Ethers are generally formed by the reaction of alcohols or alkyl halides in the presence of a base or through dehydration reactions.
- The general structure of an ether is R-O-R', where R and R' can be the same or different alkyl groups.

2. **Identifying Mixed Ethers:**
- A mixed ether is formed when the two alkyl groups (R and R') are different. For example, CH3-O-CH2CH3 is a mixed ether because the groups are methyl (CH3) and ethyl (CH2CH3).

3. **Analyzing the Reactions:**
- We need to evaluate the given reactions to see which one produces an ether where both alkyl groups are the same, thus not forming a mixed ether.

4. **Evaluating Each Option:**
- **Option 1:** Grignard reagent with an alkyl halide (e.g., CH3MgBr + CH3Cl). This will yield CH3-O-CH3 (dimethyl ether), which is not a mixed ether.
- **Option 2:** Reaction of ethanol with methyl iodide (C2H5OH + CH3I) will yield C2H5-O-CH3 (ethyl methyl ether), which is a mixed ether.
- **Option 3:** Reaction of ethanol with itself under acidic conditions (C2H5OH + C2H5OH). This will yield C2H5-O-C2H5 (diethyl ether), which is not a mixed ether.
- **Option 4:** Reaction of ethanol with a strong acid at high temperature (413K) will lead to the formation of an ether, but since both groups are ethyl, it will not be a mixed ether.

5. **Conclusion:**
- The reactions that do not yield mixed ethers are those where both alkyl groups are the same. Therefore, the correct answer is the one where the same alkyl group is used on both sides of the ether linkage.

### Final Answer:
The reaction that will not form a mixed ether is the one where both alkyl groups are the same, such as the reaction of ethanol with itself or with a reagent that leads to the same alkyl groups on both sides of the ether. Thus, the answer is **Option 4**.