Primary alcohols can be obtained can be obtained from the reaction of the RMgX with

Options

A. `CO_(2)`
B. HCHO
C. `CH_(3) CHO`
D. `H_(2) O`

Answer

To determine how primary alcohols can be obtained from the reaction of RMgX (a Grignard reagent), we need to analyze the possible reactants and their reactions with RMgX.

### Step-by-Step Solution:

1. **Understanding Grignard Reagents (RMgX)**:
- RMgX is a Grignard reagent where R is an alkyl or aryl group, and X is a halogen (like Cl, Br, or I).
- Grignard reagents are strong nucleophiles, meaning they have a high tendency to donate electrons.

2. **Identifying Primary Alcohols**:
- A primary alcohol is characterized by the hydroxyl group (-OH) being attached to a carbon that is connected to only one other carbon atom (i.e., it is bonded to one alkyl group).
- Example: Ethanol (CH3CH2OH) is a primary alcohol.

3. **Analyzing the Given Options**:
- We need to evaluate the reactions of RMgX with the provided compounds to see which one yields a primary alcohol.

4. **Option 1: CO2**:
- When RMgX reacts with CO2, the nucleophile (R-) attacks the carbon of CO2, leading to the formation of a carboxylic acid after hydrolysis.
- **Conclusion**: This does not yield a primary alcohol.

5. **Option 2: HCHO (Formaldehyde)**:
- When RMgX reacts with HCHO, the R- attacks the carbon of the aldehyde.
- The product formed is RCH2OH after hydrolysis, which is a primary alcohol because the carbon with the -OH group is attached to only one alkyl group.
- **Conclusion**: This yields a primary alcohol.

6. **Option 3: Acetaldehyde (CH3CHO)**:
- In this reaction, R- will attack the carbon of the acetaldehyde.
- The resulting product after hydrolysis will be a secondary alcohol (RCH(OH)CH3) since the carbon with the -OH group is attached to two alkyl groups.
- **Conclusion**: This does not yield a primary alcohol.

7. **Option 4: Water**:
- When RMgX reacts with water, it forms an alkane (RH) and a magnesium hydroxide compound (MgXOH).
- **Conclusion**: This does not yield a primary alcohol.

8. **Final Conclusion**:
- The only option that results in a primary alcohol when reacted with RMgX is option 2 (HCHO).

### Final Answer:
**Primary alcohols can be obtained from the reaction of RMgX with HCHO (formaldehyde).**

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