Which of the following statement is not correct ?

Options

A. generally Tollen's reagent is used in detection of unsaturation
B. Fehling solution is used in detection of glucose
C. neutral `FeCl_3` is used in detection of phenol
D. `NaHSO_3` is used in detection of carbonyl compound

Answer

To solve the question of which statement is not correct, we will analyze each of the given statements one by one.

### Step 1: Analyze the first statement
**Statement:** Tollen's reagent is used in the detection of unsaturation (double bonds and triple bonds).

**Analysis:** Tollen's reagent is specifically used to detect aldehydes, not unsaturation. Therefore, this statement is incorrect.

### Step 2: Analyze the second statement
**Statement:** Fehling's solution is used in the detection of glucose.

**Analysis:** Fehling's solution is indeed used to detect reducing sugars, including glucose. This statement is correct.

### Step 3: Analyze the third statement
**Statement:** Neutral FeCl3 is used in the detection of phenol.

**Analysis:** Neutral FeCl3 reacts with phenols to form a colored complex (often violet), indicating the presence of phenol. This statement is correct.

### Step 4: Analyze the fourth statement
**Statement:** NaHSO3 is used in the detection of carbonyl compounds.

**Analysis:** Sodium bisulfite (NaHSO3) reacts with carbonyl compounds (both aldehydes and ketones) to form bisulfite adducts, indicating the presence of carbonyl groups. This statement is correct.

### Conclusion
After analyzing all the statements, the only incorrect statement is the first one regarding Tollen's reagent. Thus, the answer to the question is:

**Answer:** The statement that is not correct is the first one: "Tollen's reagent is used in the detection of unsaturation."

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