Which of the following species will give aldol condensation?

Options

A. HCHO
B. Salicyldehyde
C. `(CH_(3))_(3)C CHO`
D. `PhCH_(2)CHO`

Answer

To determine which species will undergo aldol condensation, we need to follow these steps:

### Step 1: Understand the Requirements for Aldol Condensation
Aldol condensation requires:
- The presence of at least one aldehyde or ketone.
- The presence of at least one alpha hydrogen (hydrogens attached to the carbon adjacent to the carbonyl group).

### Step 2: Analyze Each Given Option
We will evaluate each option to see if it meets the criteria for aldol condensation.

#### Option A: HCHO (Formaldehyde)
- **Type**: Aldehyde
- **Alpha Hydrogen**: No alpha hydrogen is present because there is no alpha carbon (the carbon attached to the carbonyl carbon).
- **Conclusion**: Does not undergo aldol condensation.

#### Option B: Salicylic Aldehyde
- **Structure**: Contains a benzene ring with an -OH group and an -CHO group.
- **Alpha Hydrogen**: There are no alpha hydrogens because the carbon adjacent to the carbonyl is fully bonded (no hydrogens available).
- **Conclusion**: Does not undergo aldol condensation.

#### Option C: CH3CHO (Acetaldehyde)
- **Type**: Aldehyde
- **Alpha Hydrogen**: There is one alpha hydrogen present (the methyl group has three hydrogens).
- **Conclusion**: Undergoes aldol condensation.

#### Option D: pH-CH2-CHO
- **Structure**: Contains a phenyl group (pH) and an aldehyde group (CHO).
- **Alpha Hydrogen**: The CH2 group has two alpha hydrogens.
- **Conclusion**: Undergoes aldol condensation.

### Final Conclusion
Among the given options:
- **Option C (CH3CHO)** and **Option D (pH-CH2-CHO)** will undergo aldol condensation.
- **Options A (HCHO)** and **B (Salicylic Aldehyde)** will not.

### Summary of Results
- **Aldol Condensation Possible**: CH3CHO, pH-CH2-CHO
- **Aldol Condensation Not Possible**: HCHO, Salicylic Aldehyde

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