Optical Activity and Chiral Molecules

The video tutorial covers optical activity, explaining how to determine if a molecule is optically active or inactive. It discusses enantiomers, their configurations, and how they affect plane polarized light. The tutorial also explains specific rotation, optical purity, and enantiomeric excess, providing formulas and a practice problem to calculate specific rotation.

What is the term used to describe a molecule that can rotate plane-polarized light?

• Optically active

• Symmetrical

• Optically inactive

• Achiral

Which of the following is true about enantiomers?

• They have different solubilities.

• They have identical optical properties.

• They have different boiling points.

• They are mirror images of each other.

What does the R/S configuration of a chiral center indicate?

• The physical properties of the molecule

• The direction of light rotation

• The solubility of the molecule

• The configuration at the chiral center

What happens to plane-polarized light when it passes through an achiral molecule?

• It remains unchanged.

• It rotates to the right.

• It rotates to the left.

• It is absorbed completely.

How is specific rotation calculated?

• By dividing the observed rotation by the path length and concentration

• By multiplying the observed rotation by the path length

• By adding the observed rotation to the path length

• By dividing the observed rotation by the concentration

What is the relationship between enantiomeric excess and optical purity?

• Optical purity is twice the enantiomeric excess.

• They are unrelated.

• Enantiomeric excess is the square of optical purity.

• They are equivalent in decimal form.

Which of the following is NOT a factor in determining specific rotation?

• Temperature

• Observed rotation

• Path length

• Concentration

What is the significance of the sodium D line in specific rotation calculations?

• It determines the temperature.

• It provides a standard wavelength.

• It measures the concentration.

• It indicates the path length.

If a sample has 80% R and 20% S enantiomers, what is the enantiomeric excess?

• 100%

• 20%

• 80%

• 60%

What unit is used to measure the path length in specific rotation calculations?

• Millimeters

• Decimeters

• Meters

• Centimeters