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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5:37 minutes

Problem 42c,d

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

Verified step by step guidance

Step 1: Understand the concept of cis-trans isomerism. Cis-trans isomerism occurs in alkenes where there are two different groups attached to each carbon of the double bond. The 'cis' isomer has the same groups on the same side of the double bond, while the 'trans' isomer has them on opposite sides.

Step 2: Analyze hex-3-ene. Hex-3-ene is an alkene with a double bond between the third and fourth carbon atoms in a six-carbon chain. Check if the groups attached to the double-bonded carbons allow for cis-trans isomerism. Use MathML to represent the structure:

C_{3} = C_{4}

Step 3: Draw and label the isomers for hex-3-ene. If cis-trans isomerism is possible, draw the 'cis' isomer with similar groups on the same side and the 'trans' isomer with similar groups on opposite sides. Use E-Z nomenclature if the groups are different in priority according to Cahn-Ingold-Prelog rules.

Step 4: Analyze 1,1-dibromopropene. This compound has a double bond between the first and second carbon atoms, with two bromine atoms attached to the first carbon. Since both bromine atoms are on the same carbon, cis-trans isomerism is not possible. Use MathML to represent the structure:

C_{1} = C_{2}

Step 5: Conclude which compounds show cis-trans isomerism. Hex-3-ene can exhibit cis-trans isomerism due to the different groups attached to the double-bonded carbons, while 1,1-dibromopropene cannot due to identical groups on one carbon.

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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 alkenes where two different groups are attached to each carbon of the double bond. In the 'cis' isomer, similar groups are on the same side, while in the 'trans' isomer, they are on opposite sides. This type of isomerism is crucial for understanding the spatial arrangement of molecules and their chemical properties.

E-Z Nomenclature

E-Z nomenclature is a more comprehensive system for describing the stereochemistry of double bonds, especially when more than two different substituents are present. 'E' (from the German 'entgegen') indicates that the higher priority groups are on opposite sides, while 'Z' (from 'zusammen') means they are on the same side. Priority is determined by the Cahn-Ingold-Prelog rules, which consider atomic number and connectivity.

Alkene Structure and Substitution

The structure of alkenes, characterized by a carbon-carbon double bond, is pivotal in determining their ability to exhibit isomerism. For cis-trans isomerism to occur, each carbon in the double bond must have two different substituents. In hex-3-ene, the double bond is between the third and fourth carbon, allowing for isomerism, while in 1,1-dibromopropene, the substituents on one carbon are identical, preventing cis-trans isomerism.

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Related Practice

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.

e. 2,3-dimethylpent-2-ene

f. 3,4-dibromocyclopentene

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

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

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

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