How many of these compounds can reduce Tollen's reagent here?
`HCHO, Ph-CHO, Ph-COCH_(3), CH_(3)COCH_(3), CH_(3)-underset(O)underset(||)CH_(2)OH`
Glucose, `CH_(3)CH_(2)OH`

Answer

To determine how many of the given compounds can reduce Tollen's reagent, we need to identify which of these compounds are either aldehydes or can be tautomerized to form aldehydes, as Tollen's reagent is known to react with aldehydes and certain α-hydroxy ketones.

Let's analyze each compound:

1. **HCHO (Formaldehyde)**: This is an aldehyde and can reduce Tollen's reagent.

2. **Ph-CHO (Benzaldehyde)**: This is also an aldehyde and can reduce Tollen's reagent.

3. **Ph-COCH₃ (Acetophenone)**: This is a ketone and does not reduce Tollen's reagent directly. However, it can tautomerize to form an α-hydroxy ketone (which can be considered as a compound with a carbonyl group adjacent to a hydroxyl group), but it does not have the necessary structure to reduce Tollen's reagent.

4. **CH₃COCH₃ (Acetone)**: This is a ketone and does not reduce Tollen's reagent.

5. **CH₃-CO-CH₂OH (Hydroxyacetone)**: This is an α-hydroxy ketone and can tautomerize to form an aldehyde (specifically, it can form an enol that can be converted to an aldehyde), thus it can reduce Tollen's reagent.

6. **Glucose (C₆H₁₂O₆)**: Glucose has an aldehyde group in its structure (the carbonyl group at one end), so it can reduce Tollen's reagent.

7. **CH₃CH₂OH (Ethanol)**: This is an alcohol and does not reduce Tollen's reagent.

Now, summarizing the findings:
- HCHO: Yes (aldehyde)
- Ph-CHO: Yes (aldehyde)
- Ph-COCH₃: No (ketone)
- CH₃COCH₃: No (ketone)
- CH₃-CO-CH₂OH: Yes (α-hydroxy ketone)
- Glucose: Yes (aldehyde)
- CH₃CH₂OH: No (alcohol)

The compounds that can reduce Tollen's reagent are:
1. HCHO
2. Ph-CHO
3. CH₃-CO-CH₂OH
4. Glucose

Thus, the total number of compounds that can reduce Tollen's reagent is **4**.

### Summary of the Solution Steps:
1. Identify each compound and determine if it is an aldehyde or can tautomerize to form an aldehyde.
2. List the compounds that can reduce Tollen's reagent.
3. Count the total number of compounds that can reduce Tollen's reagent.