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Chapter 4: Q-81P (page 183)

Question:A solution of an unknown compound (3.0 g of the compound in 200 mL of solution), when placed in a polarimeter tube 2.0 dm long, was found to rotate

the plane of polarized light 18° in a counterclockwise direction. What is the specific rotation of the compound?

Short Answer

Expert verified

Specific rotation of the compound is -60.

Step by step solution

01

Explanation of formula

The specific rotation at aspecified temperature and wavelength can be calculated from the observed rotation using the formula,

Where,

[𝜶] = the specific rotation,

T= temperature in degrees Celsius,

l =is the wavelength of theincident light (when the sodium D-line is used,lis indicated as D),

𝜶= The observed rotation,

02

Calculation

Concentration of the compound (c) = = 0.015 g/ml.

Observed rotation (𝜶) = -18° as rotation is counter-clockwise.

Length of the polarimeter = 20cm.

So, the specific rotation = = -60.

The specific rotation of the compound is -60.

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Most popular questions from this chapter

For many centuries, the Chinese have used extracts from a group of herbs known as ephedra to treat asthma. A compound named ephedrine has been isolated from these herbs and found to be a potent dilator of air passages in the lungs.

a. How many stereoisomers does ephedrine have?

b. The stereoisomer shown here is the one that is pharmacologically active. What is the configuration of each of the asymmetric centers?

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

The following compound has only one asymmetric centre. Why then does it have four stereoisomers?

Question:Are the following pairs identical, enantiomers, diastereomers, or constitutional isomers?

Question: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 polarimetertube 10 cm long. What is the percent of each enantiomer in the solution?
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