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

Constitutional Isomers vs. Stereoisomers

Organic Chemistry

5. Chirality

Constitutional Isomers vs. Stereoisomers

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5:13 minutes

Problem 5

Textbook Question

Make a model and draw a three-dimensional structure for each compound. Then draw the mirror image of your original structure and determine whether the mirror image is the same compound. Label each structure as being chiral or achiral, and label pairs of enantiomers.a. cis-1,2-dimethylcyclobutaneb. trans-1,2-dimethylcyclobutane

Verified step by step guidance

Start by drawing the basic cyclobutane ring structure for both compounds. Cyclobutane is a four-membered ring, so sketch a square to represent this.

For cis-1,2-dimethylcyclobutane, place the two methyl groups (CH₃) on adjacent carbon atoms (1 and 2) on the same side of the ring. This means both methyl groups will be either both above or both below the plane of the ring.

For trans-1,2-dimethylcyclobutane, place the two methyl groups on adjacent carbon atoms (1 and 2) on opposite sides of the ring. One methyl group will be above the plane of the ring, and the other will be below.

Draw the mirror image of each structure. For the cis isomer, the mirror image will have the methyl groups still on the same side, while for the trans isomer, the mirror image will have the methyl groups on opposite sides.

Determine chirality: cis-1,2-dimethylcyclobutane is achiral because it has a plane of symmetry. Trans-1,2-dimethylcyclobutane is also achiral because it has a center of symmetry. Therefore, neither compound has enantiomers.

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Key Concepts

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

Chirality

Chirality refers to the geometric property of a molecule that makes it non-superimposable on its mirror image. A chiral molecule typically has at least one carbon atom bonded to four different substituents, resulting in two distinct forms known as enantiomers. Understanding chirality is crucial for determining the optical activity and biological interactions of compounds.

Enantiomers

Enantiomers are a pair of chiral molecules that are mirror images of each other. They possess identical physical properties, such as melting and boiling points, but differ in their interaction with polarized light and in their reactivity in chiral environments. Identifying enantiomers is essential in organic chemistry, especially in pharmaceuticals, where different enantiomers can have vastly different biological effects.

Cis-Trans Isomerism

Cis-trans isomerism, also known as geometric isomerism, occurs in compounds with restricted rotation around a double bond or a ring structure. In the context of cyclobutane derivatives, 'cis' indicates that substituents are on the same side of the ring, while 'trans' indicates they are on opposite sides. This distinction is important for determining the overall symmetry and potential chirality of the molecule.

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Related Practice

Textbook Question

Define the relationship between each set of two molecules as chain isomers, positional isomers, functional group isomers, enantiomers, diastereomers, conformational isomers, or identical.

(c)

Textbook Question

If the carbon atom in CH₂Cl₂ were flat, there would be two stereoisomers. The carbon atom in CH₂Cl₂is actually tetrahedral. Make a model of this compound, and determine whether there are any stereoisomers of CH₂Cl₂.

Textbook Question

Which of the following compounds are capable of being resolved into enantiomers?

(g)

(h)

Textbook Question

Make a model and draw a three-dimensional structure for each compound. Then draw the mirror image of your original structure and determine whether the mirror image is the same compound. Label each structure as being chiral or achiral, and label pairs of enantiomers.

(a) cis-1,2-dimethylcyclobutane

(b) trans-1,2-dimethylcyclobutane

Textbook Question

For the molecules shown,

(i) count the number of stereocenters present and

(ii) draw all possible stereoisomers.

(iii) Identify the relationships between stereoisomers as enantiomers or diastereomers.

(c)

Textbook Question

Which of the following compounds are capable of being resolved into enantiomers?

(a) N-ethyl-N-methylaniline

(b) 2-methylpiperidine