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

4. Alkanes and Cycloalkanes

Cis vs Trans

Organic Chemistry

4. Alkanes and Cycloalkanes

Cis vs Trans

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3:05 minutes

Problem 17a

Textbook Question

Which of the following cycloalkanes are capable of geometric (cis-trans) isomerism? Draw the cis and trans isomers.
a. 3-ethyl-1,1-dimethylcyclohexane

Verified step by step guidance

Understand the concept of geometric (cis-trans) isomerism: Geometric isomerism occurs in cycloalkanes when there are two substituents on different carbon atoms of the ring, and these substituents can be positioned on the same side (cis) or opposite sides (trans) of the ring.

Identify the structure of 3-ethyl-1,1-dimethylcyclohexane: The cyclohexane ring has six carbon atoms. The substituents are located at the 1st and 3rd positions. At the 1st position, there are two methyl groups, and at the 3rd position, there is an ethyl group.

Determine if geometric isomerism is possible: For geometric isomerism to occur, the substituents must be on different carbon atoms and not on the same carbon atom. In this case, the substituents are on different carbon atoms (1st and 3rd), which allows for cis-trans isomerism.

Draw the cis isomer: In the cis isomer, the ethyl group at the 3rd position and one of the methyl groups at the 1st position are on the same side of the cyclohexane ring. Use wedge and dash bonds to represent the 3D orientation of the substituents.

Draw the trans isomer: In the trans isomer, the ethyl group at the 3rd position and one of the methyl groups at the 1st position are on opposite sides of the cyclohexane ring. Again, use wedge and dash bonds to show the 3D orientation.

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Key Concepts

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

Geometric Isomerism

Geometric isomerism, also known as cis-trans isomerism, occurs in compounds with restricted rotation around a bond, typically a double bond or a ring structure. In cycloalkanes, this isomerism arises when two substituents are attached to different sides of the ring, leading to distinct spatial arrangements known as cis (same side) and trans (opposite sides) isomers.

Cycloalkanes

Cycloalkanes are saturated hydrocarbons with carbon atoms arranged in a ring structure. They have the general formula CnH2n and can exhibit geometric isomerism if they have substituents that allow for different spatial arrangements. The rigidity of the ring structure restricts rotation, making it possible for cis and trans configurations to exist.

Substituent Positioning in Cycloalkanes

The positioning of substituents on a cycloalkane ring is crucial for determining the possibility of geometric isomerism. For isomerism to occur, the ring must have at least two substituents on different carbon atoms. The spatial arrangement of these substituents, either on the same side (cis) or opposite sides (trans) of the ring, defines the isomeric form.

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Imines can exist as stereoisomers. The isomers are named using the E,Z system of nomenclature (Section 4.2 ). The lone pair has the lowest priority.

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Draw the structure of each of the following compounds:

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Draw and name all stereoisomers of 3-chlorohepta-2,4-diene

a. using the cis-trans nomenclature.

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c. 1-ethyl-3-methylcyclopentane

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Which of the following cycloalkanes are capable of geometric (cis-trans) isomerism? Draw the cis and trans isomers.

b. 1-ethyl-3-methylcycloheptane

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