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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3:43 minutes

Problem 12c

Textbook Question

Which of the following alkenes are E and which are Z?
(c)

Verified step by step guidance

Step 1: Understand the E/Z nomenclature. E/Z isomerism is based on the relative positions of the highest-priority substituents on each carbon of the double bond. The priority is determined using the Cahn-Ingold-Prelog (CIP) rules.

Step 2: Identify the substituents attached to the two carbons of the double bond. In the given structure, one carbon of the double bond is attached to a hydrogen and a hydroxymethyl group (-CH2OH). The other carbon is attached to a methoxy group (-OCH3) and a cyclohexane ring.

Step 3: Assign priorities to the substituents on each carbon using the CIP rules. The substituent with the higher atomic number at the first point of difference gets higher priority. For the first carbon, hydroxymethyl (-CH2OH) has higher priority than hydrogen. For the second carbon, the cyclohexane ring has higher priority than the methoxy group (-OCH3).

Step 4: Determine the relative positions of the higher-priority substituents. If the higher-priority groups are on opposite sides of the double bond, the configuration is E (entgegen, German for 'opposite'). If they are on the same side, the configuration is Z (zusammen, German for 'together').

Step 5: Analyze the structure visually. In the given structure, the hydroxymethyl group and the cyclohexane ring (the higher-priority groups) are on opposite sides of the double bond. Therefore, the configuration of the alkene is E.

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Key Concepts

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

E/Z Isomerism

E/Z isomerism is a type of stereoisomerism that occurs in alkenes due to the restricted rotation around the double bond. The 'E' (entgegen) configuration indicates that the highest priority substituents on each carbon of the double bond are on opposite sides, while the 'Z' (zusammen) configuration indicates they are on the same side. This classification is determined using the Cahn-Ingold-Prelog priority rules.

Cahn-Ingold-Prelog Priority Rules

The Cahn-Ingold-Prelog priority rules are a set of guidelines used to assign priority to substituents attached to the double-bonded carbons in alkenes. The priority is based on the atomic number of the atoms directly attached to the double bond; higher atomic numbers receive higher priority. If the first atoms are the same, the comparison continues along the chain until a difference is found.

Alkene Structure and Geometry

Alkenes are hydrocarbons that contain at least one carbon-carbon double bond, which introduces a planar geometry around the double bond. This planar structure allows for the possibility of different spatial arrangements of substituents, leading to the formation of E/Z isomers. Understanding the geometry of alkenes is crucial for determining their stereochemical configurations.

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