The specific rotation of +12.0 for tartaric acid indicates that the substance is optically active and rotates the plane of plane-polarized light in the clockwise direction (dextrorotatory).
Explanation:
- Specific rotation is a measure of how much a chiral substance rotates plane-polarized light.
- A positive (+) value means the rotation is toward the right (clockwise), known as dextrorotation.
- A negative (−) value would indicate left (anticlockwise) rotation, known as levorotation.
Key Points:
- Tartaric acid contains chiral carbon atoms, which cause optical activity
- The value +12.0 represents the degree of rotation under specific conditions (temperature, wavelength, concentration)
- Optical activity confirms that the compound is not a racemic mixture
Conclusion:
A specific rotation of +12.0 indicates that tartaric acid is optically active and dextrorotatory, meaning it rotates plane-polarized light to the right.