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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4:04 minutes

Problem 6e,f

Textbook Question

1. Determine which of the following compounds show cis-trans isomerism.
2. Draw and name the cis and trans (or Z and E) isomers of those that do.
e. 2,3-dimethylpent-2-ene
f. 3,4-dibromocyclopentene

Verified step by step guidance

Identify the structural features necessary for cis-trans isomerism: For alkenes, look for a double bond with different groups attached to each carbon of the double bond. For cyclic compounds, look for substituents on different carbons that can be positioned above or below the plane of the ring.

Examine compound e, 2,3-dimethylpent-2-ene: This compound has a double bond between the second and third carbon atoms. Check if the groups attached to these carbons are different, which is necessary for cis-trans isomerism.

For 2,3-dimethylpent-2-ene, the groups attached to the double-bonded carbons are: on C2, a methyl group and a hydrogen; on C3, a methyl group and the rest of the carbon chain. Since there are different groups on each carbon, this compound can exhibit cis-trans isomerism.

Examine compound f, 3,4-dibromocyclopentene: This is a cyclic compound with a double bond. Check if the bromine atoms are on different carbons and can be positioned above or below the plane of the ring, which allows for cis-trans isomerism.

For 3,4-dibromocyclopentene, the bromine atoms are on C3 and C4. Since these can be positioned differently relative to the plane of the ring, this compound can also exhibit cis-trans isomerism. Draw the structures for both compounds, labeling the isomers as 'cis' (same side) and 'trans' (opposite sides) for alkenes, or 'Z' and 'E' for more complex cases.

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Key Concepts

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

Cis-Trans Isomerism

Cis-trans isomerism, also known as geometric isomerism, occurs in compounds with restricted rotation around a bond, typically a double bond or a ring structure. It involves the arrangement of substituents around the bond, where 'cis' indicates substituents on the same side and 'trans' indicates substituents on opposite sides. This isomerism affects the physical and chemical properties of the compounds.

E-Z Nomenclature

E-Z nomenclature is a system used to describe the stereochemistry of double bonds in organic compounds. It is based on the Cahn-Ingold-Prelog priority rules, where 'E' (from German 'entgegen') indicates that the highest priority groups are on opposite sides of the double bond, and 'Z' (from German 'zusammen') indicates they are on the same side. This system is particularly useful for complex molecules where cis-trans terminology is insufficient.

Double Bond and Ring Structures

Double bonds and ring structures are key features that can lead to cis-trans isomerism. A double bond restricts rotation, creating a fixed spatial arrangement of substituents, while ring structures can also prevent rotation due to their cyclic nature. Understanding these structural elements is crucial for identifying potential geometric isomers in organic compounds.

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Related Practice

Textbook Question

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

b. using the E-Z nomenclature.

Textbook Question

Some of the following examples can show geometric isomerism, and some cannot. For the ones that can, draw all the geometric isomers, and assign complete names using the E-Z system.

c. 3-bromo-2-methylhex-3-ene

d. penta-1,3-diene

Textbook Question

Some of the following examples can show geometric isomerism, and some cannot. For the ones that can, draw all the geometric isomers, and assign complete names using the E-Z system.

a. 3-bromo-2-chloropent-2-ene

b. 3-ethylhexa-2,4-diene

Textbook Question

Label each structure as Z, E, or neither.

(a)

(b)

(c)

(d)

Textbook Question

1. Determine which of the following compounds show cis-trans isomerism.

2. Draw and name the cis and trans (or Z and E) isomers of those that do.

a. hex-3-ene

b.buta-1,3-diene

Textbook Question

Determine which compounds show cis-trans isomerism. Draw and label the isomers, using both the cis-trans and E-Z nomenclatures where applicable.

c. hex-3-ene

d. 1,1-dibromopropene

Textbook Question

Some of the following examples can show geometric isomerism, and some cannot. For the ones that can, draw all the geometric isomers, and assign complete names using the E-Z system.

(i)

Textbook Question

Some of the following examples can show geometric isomerism, and some cannot. For the ones that can, draw all the geometric isomers, and assign complete names using the E-Z system.

(g)

(h)

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1. Determine which of the following compounds show cis-trans isomerism. 2. Draw and name the cis and trans (or Z and E) isomers of those that do.e. 2,3-dimethylpent-2-ene f. 3,4-dibromocyclopentene

Key Concepts

Cis-Trans Isomerism

E-Z Nomenclature

Double Bond and Ring Structures

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1. Determine which of the following compounds show cis-trans isomerism.
2. Draw and name the cis and trans (or Z and E) isomers of those that do.
e. 2,3-dimethylpent-2-ene
f. 3,4-dibromocyclopentene