Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

5. Chirality

Optical Activity

Organic Chemistry

5. Chirality

Optical Activity

Previous problemNext problem

6:33 minutes

Problem 11

Textbook Question

If you had the two enantiomers of carvone in unmarked bottles, could you use just your nose and a polarimeter to determine
a. whether it is the (+) or (−) enantiomer that smells like spearmint
b. whether it is the (R) or (S) enantiomer that smells like spearmint?
c. With the information given in the drawings of carvone above, what can you add to your answers to (a) and (b)?

Verified step by step guidance

Step 1: Analyze the given information about carvone enantiomers. The (+)-carvone enantiomer smells like caraway seed, while the (−)-carvone enantiomer smells like spearmint. This indicates that the smell is directly related to the enantiomeric form.

Step 2: Use a polarimeter to determine the optical activity of the carvone enantiomers. A polarimeter measures the direction and degree of rotation of plane-polarized light. The (+)-enantiomer rotates light clockwise (dextrorotatory), while the (−)-enantiomer rotates light counterclockwise (levorotatory). This will help identify whether the sample is (+) or (−).

Step 3: Relate the smell to the optical activity. Based on the information provided, the (−)-carvone enantiomer smells like spearmint, and the (+)-carvone enantiomer smells like caraway seed. By combining the polarimeter data and the smell, you can determine which enantiomer corresponds to spearmint.

Step 4: Determine the absolute configuration (R or S) of the enantiomers. The drawings provided show that the (+)-carvone enantiomer has the R configuration, while the (−)-carvone enantiomer has the S configuration. This means the spearmint smell corresponds to the (S)-carvone enantiomer.

Step 5: Summarize the findings. Using both the polarimeter and the smell, you can identify the enantiomer as either (+)-carvone (R configuration, caraway seed smell) or (−)-carvone (S configuration, spearmint smell). The drawings confirm the relationship between optical activity, absolute configuration, and smell.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above

Video duration:

Play a video:

Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Enantiomers

Enantiomers are a type of stereoisomer that are non-superimposable mirror images of each other. They have the same molecular formula and connectivity but differ in the spatial arrangement of atoms. This difference can lead to distinct physical properties, such as smell, as seen with (+)-carvone and (−)-carvone, which smell like caraway seed and spearmint, respectively.

Optical Activity

Optical activity refers to the ability of chiral compounds to rotate the plane of polarized light. This property is measured using a polarimeter, which quantifies the angle of rotation. Each enantiomer will rotate light in opposite directions; thus, a polarimeter can help distinguish between the (+) and (−) forms of carvone based on their specific rotations.

Chirality and R/S Nomenclature

Chirality is a property of a molecule that has a non-superimposable mirror image, often due to the presence of a chiral center, typically a carbon atom bonded to four different groups. The R/S nomenclature system is used to assign configurations to these chiral centers, helping to identify the specific enantiomer. Understanding this system is crucial for determining whether the enantiomer that smells like spearmint is (R) or (S) carvone.

Watch next

Master Specific rotation vs. observed rotation. with a bite sized video explanation from Johnny

Start learning

Related Videos

Related Practice

Textbook Question

Draw the structure for a compound with molecular formula C₂H₂I₂F₂

c. that is optically active.

Textbook Question

A solution of 0.50 g of (−)-epinephrine (see Figure 5-16) dissolved in 10.0 mL of dilute aqueous HCl was placed in a 20-cm polarimeter tube. Using the sodium D line, the rotation was found to be −5.1° at 25 °C. Determine the specific rotation of epinephrine.

<IMAGE>

Textbook Question

Calculate the specific rotations of the following samples taken at 25 °C using the sodium D line.

a. 1.00 g of sample is dissolved in 20.0 mL of ethanol. Then 5.00 mL of this solution is placed in a 20.0-cm polarimeter tube. The observed rotation is 1.25° counterclockwise.

Textbook Question

Calculate the specific rotations of the following samples taken at 25 °C using the sodium D line.

b. 0.050 g of sample is dissolved in 2.0 mL of ethanol, and this solution is placed in a 2.0-cm polarimeter tube. The observed rotation is clockwise 0.043°.

Textbook Question

Draw the mirror images of glucose and fructose. Are glucose and fructose chiral? Do you expect them to be optically active?

Textbook Question

Draw the mirror images of glucose and fructose. Are glucose and fructose chiral? Do you expect them to be optically active?

Textbook Question

Explain how R and S are related to (+) and (-).

Textbook Question

The reaction of (R)-1-iodo-2-methylbutane with hydroxide ion forms an alcohol without breaking any bonds to the asymmetric center. The alcohol rotates the plane of polarization of plane-polarized light counterclockwise. What is the configuration of (+)-2-methyl-1-butanol?

Show more practices

Download the Mobile app

Privacy

Do not sell my personal information

Accessibility

Patent notice

Sitemap