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

16. Conjugated Systems

Cumulative Electrocyclic Problems

Organic Chemistry

16. Conjugated Systems

Cumulative Electrocyclic Problems

Previous problemNext problem

7:08 minutes

Problem 7a

Textbook Question

Which of the following are correct? Correct any false statements.
a. A conjugated diene with an even number of double bonds undergoes conrotatory ring closure under thermal conditions.

Verified step by step guidance

Step 1: Understand the concept of conrotatory and disrotatory ring closure. These terms describe the stereochemical outcome of electrocyclic reactions, which are governed by the Woodward-Hoffmann rules. Conrotatory means that the substituents on the termini of the conjugated system rotate in the same direction during the ring closure, while disrotatory means they rotate in opposite directions.

Step 2: Recall the Woodward-Hoffmann rules for electrocyclic reactions. These rules state that the stereochemical outcome (conrotatory or disrotatory) depends on the number of π-electrons in the conjugated system and whether the reaction occurs under thermal or photochemical conditions.

Step 3: Apply the rule for thermal conditions. For a conjugated diene (4 π-electrons, an even number), the reaction undergoes conrotatory ring closure under thermal conditions. This is consistent with the Woodward-Hoffmann rules, which predict conrotatory closure for systems with 4n π-electrons (where n is an integer) under thermal conditions.

Step 4: Verify the statement in the problem. The statement claims that a conjugated diene with an even number of double bonds undergoes conrotatory ring closure under thermal conditions. Since a conjugated diene has 4 π-electrons (2 double bonds), the statement is correct as per the rules.

Step 5: Conclude that the statement is correct and does not require any correction. If there were any false statements, you would need to identify the error and provide the corrected version based on the rules.

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.

Conjugated Dienes

Conjugated dienes are compounds that contain two double bonds separated by a single bond, allowing for delocalization of π electrons. This delocalization enhances stability and reactivity, making conjugated systems important in organic reactions, particularly in cycloaddition and polymerization processes.

Electrocyclic Reactions

Electrocyclic reactions involve the conversion of a conjugated system into a cyclic structure through the breaking and forming of σ and π bonds. The stereochemistry of these reactions is influenced by the number of π bonds and the reaction conditions, with conrotatory and disrotatory mechanisms being key concepts in determining the outcome.

Thermal vs. Photochemical Conditions

The conditions under which a reaction occurs significantly affect its mechanism. Under thermal conditions, electrocyclic reactions involving conjugated dienes with an even number of π bonds typically proceed via a conrotatory mechanism, while photochemical conditions favor a disrotatory mechanism. Understanding these conditions is crucial for predicting the correct reaction pathway.

Watch next

Master Two Steps to Predicting Any Electrocyclic Products with a bite sized video explanation from Johnny

Start learning