A compound of molecular formula ` C_(8)H_(8)O_(2)` reacts with acetophenone is form a single cross-aldol product in the presence of base. The same compound on reaction with conc. NaOH forms benzyl alcohol as one of the products. The structure of the compounds is :

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Answer

To solve the problem, we need to determine the structure of a compound with the molecular formula C8H8O2 that reacts with acetophenone to form a single cross-aldol product and also yields benzyl alcohol when reacted with concentrated NaOH.

### Step-by-Step Solution:

1. **Identify the Molecular Formula**:
The compound has the molecular formula C8H8O2. This indicates that it contains 8 carbon atoms, 8 hydrogen atoms, and 2 oxygen atoms.

2. **Understand the Reaction Conditions**:
The compound reacts with acetophenone (which has the structure C6H5C(O)CH3) in the presence of a base to form a single cross-aldol product. This suggests that the compound does not have an alpha hydrogen atom, which is necessary for self-condensation.

3. **Consider the Aldehyde Group**:
The compound must contain an aldehyde group (-CHO) because it undergoes a cross-aldol reaction. In addition, it should not have any alpha hydrogen atoms to prevent self-condensation.

4. **Analyze the Canizaro Reaction**:
The compound also reacts with concentrated NaOH to form benzyl alcohol, indicating that it undergoes a Canizaro reaction. For a compound to undergo this reaction, it must have an aldehyde group and no alpha hydrogens.

5. **Propose Possible Structures**:
Given the requirements, we can propose the structure of the compound. The structure that fits all the criteria is 4-methoxybenzaldehyde (4-methoxybenzylaldehyde), which has the structure:
- A benzene ring with a methoxy group (-OCH3) at the para position and an aldehyde group (-CHO).

6. **Verify the Structure**:
- The structure of 4-methoxybenzaldehyde is C8H8O2.
- It does not have alpha hydrogens, satisfying the condition for a single cross-aldol product.
- It can undergo the Canizaro reaction, yielding benzyl alcohol as one of the products.

7. **Write the Reactions**:
- **Cross-Aldol Reaction**:
4-methoxybenzaldehyde + acetophenone → Cross-aldol product.
- **Canizaro Reaction**:
4-methoxybenzaldehyde + NaOH → Benzyl alcohol + Sodium salt of 4-methoxybenzaldehyde.

### Conclusion:
The structure of the compound is **4-methoxybenzaldehyde**.