Assertion: Hydrolysis of sucrose brings about a change in sign of rotation from dextro to laevo.
Reason: Hydrolysis always changes the optical rotation of a compound.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are true but reason is not the correct explanation of assertion.
C. If assertion is true but reason is false.
D. If both assertion and reason are false.

Explanation

To solve the assertion and reason question regarding the hydrolysis of sucrose, we will analyze both statements step by step.

### Step 1: Understand the Assertion
The assertion states that hydrolysis of sucrose brings about a change in sign of rotation from dextro to laevo.

- **Explanation**: Sucrose is a disaccharide composed of glucose and fructose. In its original form, sucrose is dextrorotatory, meaning it rotates plane-polarized light to the right (positive rotation). Upon hydrolysis, sucrose breaks down into its constituent monosaccharides: alpha-glucose (which is also dextrorotatory) and beta-fructose (which is levorotatory).

### Step 2: Analyze the Optical Rotation
- **Dextrorotatory Glucose**: +52.5 degrees
- **Levorotatory Fructose**: -92.4 degrees

When these two sugars are mixed after hydrolysis, the overall optical rotation will depend on the relative contributions of each sugar's rotation.

### Step 3: Calculate the Overall Rotation
- The rotation from glucose is positive, while the rotation from fructose is negative. Since the absolute value of the rotation from fructose is greater than that of glucose, the overall rotation after hydrolysis will be negative (levo).

### Conclusion for Assertion
Thus, the assertion is correct: hydrolysis of sucrose does indeed change the sign of rotation from dextrorotatory to levorotatory.

### Step 4: Understand the Reason
The reason states that hydrolysis always changes the optical rotation of a compound.

- **Explanation**: While hydrolysis can change the optical rotation of some compounds, it is not a universal rule that it will change the optical rotation for all compounds. Therefore, the reason is not necessarily true in all cases.

### Conclusion for Reason
Thus, the reason is incorrect: hydrolysis does not always change the optical rotation of every compound.

### Final Answer
- The assertion is correct, while the reason is incorrect. Therefore, the answer to the question is option C.

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