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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6:45 minutes

Problem 6c,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.
c. hexa-2,4-diene
d. 3-methylpent-2-ene

Verified step by step guidance

Step 1: Understand the concept of cis-trans isomerism, also known as geometric isomerism. This occurs in alkenes where there is restricted rotation around the double bond, and each carbon in the double bond has two different groups attached.

Step 2: Analyze compound c, hexa-2,4-diene. This compound has two double bonds. Check each double bond to see if it can exhibit cis-trans isomerism. For cis-trans isomerism to occur, each carbon in the double bond must have two different substituents.

Step 3: Analyze compound d, 3-methylpent-2-ene. Look at the double bond between the second and third carbon atoms. Determine if each carbon in the double bond has two different groups attached, which is necessary for cis-trans isomerism.

Step 4: For compounds that exhibit cis-trans isomerism, draw the structural formulas for both the cis and trans isomers. In cis isomers, similar groups are on the same side of the double bond, while in trans isomers, they are on opposite sides.

Step 5: Name the isomers using the IUPAC naming system. For compounds with more complex substituents, use the E/Z nomenclature, where Z (zusammen) indicates the higher priority groups are on the same side, and E (entgegen) indicates they are on opposite sides.

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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. It requires two different groups attached to each carbon of the double bond. Cis isomers have similar groups on the same side, while trans isomers have them on opposite sides.

Z and E Nomenclature

Z and E nomenclature is used to describe the stereochemistry of double bonds when there are more than two substituents. Z (zusammen) indicates that the higher priority groups are on the same side, while E (entgegen) indicates they are on opposite sides. Priority is determined using Cahn-Ingold-Prelog rules.

Identifying Isomerism in Alkenes

To determine if an alkene can exhibit cis-trans isomerism, check for a double bond with two different substituents on each carbon. In hexa-2,4-diene, the double bonds allow for potential isomerism, while in 3-methylpent-2-ene, the substituents on the double bond carbons must be evaluated for differences.

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Related Practice

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)

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.

e. 3-ethyl-5-methyloct-3-ene

f. 3,7-dichloroocta-2,5-diene

Textbook Question

Give a correct name for each compound.

(c)

(d)

Textbook Question

What is each compound's systematic name?

Textbook Question

The following names are all incorrect. Draw the structure represented by the incorrect name (or a consistent structure if the name is ambiguous), and give your drawing the correct name.

a. cis-dimethylpent-2-ene

b. 3-vinylhex-4-ene

Textbook Question

Give a correct name for each compound.

(e)

(f)

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