A carbonyl compound gives a positive lodoform test but but does
not reduce Tollen's reagent or Fehling's solution. It forms a cyanohydrin with HCN, which on hydrolysis gives a hydroxy acid
with a methyl side chain. The compound :-

Options

A. Acetaldehyde
B. Propionaldehyde
C. Acetone
D. Crotonaldehyde

Answer

To solve the problem, we need to analyze the information given about the carbonyl compound step by step.

### Step 1: Identify the characteristics of the carbonyl compound
The compound gives a positive iodoform test, does not reduce Tollen's reagent or Fehling's solution, and forms a cyanohydrin with HCN which on hydrolysis gives a hydroxy acid with a methyl side chain.

### Step 2: Understand the iodoform test
The iodoform test is positive for methyl ketones (compounds of the form RCOCH3) and some aldehydes. Since the compound does not reduce Tollen's reagent or Fehling's solution, it suggests that the compound is likely a ketone rather than an aldehyde.

### Step 3: Analyze the reduction tests
- **Tollen's reagent**: This reagent is used to test for aldehydes. Aldehydes reduce Tollen's reagent to silver, while ketones do not. Since the compound does not reduce Tollen's reagent, it cannot be an aldehyde.
- **Fehling's solution**: Similar to Tollen's reagent, Fehling's solution is also used to test for aldehydes. Ketones do not reduce Fehling's solution either.

### Step 4: Determine the type of carbonyl compound
Given that the compound gives a positive iodoform test and does not reduce Tollen's or Fehling's reagents, we conclude that the compound is a methyl ketone.

### Step 5: Forming a cyanohydrin
The compound forms a cyanohydrin with HCN. The general reaction for a ketone with HCN is:
\[ RCOCH_3 + HCN \rightarrow RCOH(CN)CH_3 \]
This indicates that the carbonyl carbon is bonded to a cyanide group.

### Step 6: Hydrolysis of the cyanohydrin
Upon hydrolysis, the cyanohydrin will convert to a hydroxy acid. The hydrolysis reaction can be represented as:
\[ RCOH(CN)CH_3 + H_2O \rightarrow RCOOH + CH_3OH \]
This gives a hydroxy acid with a methyl side chain.

### Step 7: Identify the specific compound
The only methyl ketone that fits all these criteria is acetone (CH3COCH3). When acetone reacts with HCN, it forms acetone cyanohydrin, which upon hydrolysis yields 2-hydroxy-2-methylpropanoic acid (a hydroxy acid with a methyl side chain).

### Conclusion
The carbonyl compound in question is **acetone (CH3COCH3)**.

---