Question

Polarimetry and the Optical Activity of Sucrose

1. What kind of molecules will exhibit the property of optical activity?

2. How many chiral centers does sucrose have?

3. The LD-50 (acute oral toxicity for a rat) is 29,700 mg/kg. What mass, in grams, of sucrose would be needed to kill 50% of the population of 150-lb rats?

Answer 1

1) Optical activity is the rotation of plane polarised ligh in the clockwise or counter clockwise direction shown by chiral molecules. These molecules have an symmetric carbon center i.e. where the carbon atom is attached to four different group.

2) Sucrose is a combination of glucose + fructose and has 9 chiral centers.

3) Total mass of the rat population = 150 lb = 68 kg

Mass of 50% of population = 50/100*68 = 34 kg

Lethal dose needed to kill 50% of population = LD-50 = 34 * 29700 = 1009,800 mg = 1009.8 g

Lethal dose LD-50