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

5:08 minutes

Problem 12b

Textbook Question

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

Verified step by step guidance

Step 1: Understand the E/Z nomenclature. E (entgegen) and Z (zusammen) are used to describe the relative positions of the substituents on either side of a double bond. E means the higher-priority groups are on opposite sides, while Z means they are on the same side.

Step 2: Assign priorities to the substituents on each carbon of the double bond using the Cahn-Ingold-Prelog priority rules. The priority is determined based on atomic number; the higher the atomic number, the higher the priority.

Step 3: For the left carbon of the double bond, the substituents are Cl₃C (trichloromethyl group) and a hydrogen atom. Cl₃C has a higher priority because chlorine has a higher atomic number than hydrogen.

Step 4: For the right carbon of the double bond, the substituents are a methyl group (-CH₃) and a carbonyl group (-C=O). The carbonyl group has a higher priority because the oxygen atom bonded to the carbon has a higher atomic number than the hydrogen atoms in the methyl group.

Step 5: Determine the relative positions of the higher-priority groups (Cl₃C and -C=O). If they are on opposite sides of the double bond, the alkene is E. If they are on the same side, the alkene is Z.

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.

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 distinction is crucial for understanding the geometric arrangement of substituents in alkenes.

Cahn-Ingold-Prelog Priority Rules

The Cahn-Ingold-Prelog priority rules are used to determine the priority of substituents attached to the double-bonded carbons in alkenes. According to these rules, the substituent with the higher atomic number is given higher priority. If the first atoms are the same, one must consider the next atoms in the substituent chains until a difference is found, which is essential for correctly identifying E or Z configurations.

Substituent Analysis

Substituent analysis involves examining the groups attached to the double-bonded carbons to determine their relative positions. In the context of E/Z isomerism, it is important to identify the substituents on each carbon of the double bond and assess their priority. This analysis helps in visualizing the spatial arrangement of the groups, which is key to classifying the alkene as either E or Z.

Watch next

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

Start learning