A compound has a specific rotation of -39.0. A solution of the compound (0.187 g/100 mL) has an observed rotation of -6.52° when placed in a polarimeter tube 10 cm long. What is the percent of each enantiomer in the solution?

The specific rotation of (S)-2-iodobutane is +15.90°.

a. Draw the structure of (S)-2-iodobutane.

b. Predict the specific rotation of (R)-2-iodobutane.

c. Determine the percentage composition of a mixture of (R)- and (S)-2-iodobutane with a specific rotation of –7.95°.

The specific rotation of (R)-(+)-glyceraldehyde is +8.7. If the observed specific rotation of a mixture of (R)-glyceraldehyde and (S)-glyceraldehyde is +1.4, what percent of glyceraldehyde is present as the R enantiomer?

The [α] of pure S-epinephrine is +50°. Calculate the ee of a solution with an observed value of -40°. Calculate percent of each enantiomer. Then sketch the approximate mixture in our sample polarimeter tube.

A sample of (S)-(+)-lactic acid was found to have an enantiomeric excess of 72%. How much R isomer is present in the sample?

Naproxen, a nonsteroidal anti-inflammatory drug that is the active ingredient in Aleve (p. 115), has a specific rotation of +66. One commercial preparation results in a mixture with a 97% enantiomeric excess.

a. Does naproxen have the R or the S configuration?

b. What percent of each enantiomer is obtained from the commercial preparation?

A solution of pure (S)-2-iodobutane ([α] = +15.90°) in acetone is allowed to react with radioactive iodide, ¹³¹I^–, until 1.0% of the iodobutane contains radioactive iodine. The specific rotation of this recovered iodobutane is found to be +15.58°.

a. Determine the percentages of (R)- and (S)-2-iodobutane in the product mixture.

(S)-Propranolol, a drug used for the treatment of anxiety, has a specific rotation of -25.5° . Attempting to prepare it in enantiopure form, a chemist produced a compound that gave a specific rotation of -18.3° . What is the ratio of (S)- to (R)-propranolol produced by the chemist?