Specific Rotation Formula:
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Definition: Specific rotation is a property of optically active compounds that measures how much they rotate plane-polarized light.
Purpose: It helps identify and characterize chiral compounds and determine their purity or concentration.
The calculator uses the formula:
Where:
Explanation: The observed rotation is divided by the product of the path length and concentration to give the standardized specific rotation.
Details: Specific rotation is crucial in chemistry for identifying chiral molecules, determining enantiomeric excess, and characterizing substances.
Tips: Enter the observed rotation in degrees, path length in decimeters (dm), and concentration in grams per milliliter (g/mL). Length and concentration must be > 0.
Q1: What does the D subscript mean in [α]D?
A: It indicates the measurement was taken using the D-line of sodium (589 nm wavelength).
Q2: What are typical specific rotation values?
A: Values range from -180° to +180° depending on the compound. For example, sucrose is +66.5° and camphor is +44.3°.
Q3: Why is path length measured in decimeters?
A: This is the standard unit for polarimetry measurements, making specific rotation values comparable across different experiments.
Q4: How does temperature affect specific rotation?
A: Specific rotation is temperature-dependent, so measurements should include temperature (usually 20°C or 25°C).
Q5: What if my compound is in a solvent other than water?
A: The solvent should be specified (e.g., [α]D20 (c=1, CHCl3)) as it can affect the rotation.