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

Previous problemNext problem

2:47 minutes

Problem 2a

Textbook Question

Identify the following alkenes as E or Z, if appropriate.
(a)

Verified step by step guidance

Step 1: Understand the E/Z nomenclature. The E/Z system is used to describe the stereochemistry of alkenes. It is based on the Cahn-Ingold-Prelog priority rules, which assign priorities to the groups attached to the double-bonded carbons.

Step 2: Identify the two groups attached to each carbon of the double bond. For each carbon, determine the priority of the groups based on atomic number. The group with the higher atomic number gets the higher priority.

Step 3: Compare the positions of the higher-priority groups on each side of the double bond. If the higher-priority groups are on the same side of the double bond, the alkene is classified as Z (from the German word 'zusammen,' meaning 'together'). If the higher-priority groups are on opposite sides, the alkene is classified as E (from the German word 'entgegen,' meaning 'opposite').

Step 4: Apply the priority rules to the specific alkene in question. Carefully analyze the substituents on each carbon of the double bond and assign priorities.

Step 5: Based on the relative positions of the higher-priority groups, determine whether the alkene is E or Z. Ensure that you clearly document your reasoning for the assignment.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above

Video duration:

Play a video:

Was this helpful?

Key Concepts

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

Alkene Geometry

Alkenes are hydrocarbons that contain at least one carbon-carbon double bond (C=C). The geometry around the double bond is planar, leading to two possible configurations: E (entgegen) and Z (zusammen). These configurations depend on the relative positions of the substituents attached to the double-bonded carbons.

Cahn-Ingold-Prelog Priority Rules

To determine whether an alkene is E or Z, the Cahn-Ingold-Prelog priority rules are applied. These rules assign priority to substituents based on atomic number; the higher the atomic number, the higher the priority. If the highest priority groups on each carbon are on the same side, the configuration is Z; if they are on opposite sides, it is E.

Stereoisomerism

Stereoisomerism refers to the phenomenon where compounds have the same molecular formula and connectivity but differ in the spatial arrangement of atoms. In alkenes, stereoisomers can exist as E/Z isomers due to the restricted rotation around the double bond, making it essential to analyze their configurations for proper identification.

Watch next

Master How to name different types of double bonds or rings with a bite sized video explanation from Johnny

Start learning