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

10:06 minutes

Problem 45

Textbook Question

How can this transformation be carried out using only heat or light?

Verified step by step guidance

Analyze the given chemical structures: The starting material is a cis-stilbene derivative, and the product is a trans-stilbene derivative. This transformation involves the isomerization of the double bond from cis to trans configuration.

Understand the mechanism: This isomerization can be achieved using either heat or light. Heat promotes thermal isomerization, while light induces photochemical isomerization. Both methods involve breaking the π-bond temporarily to allow rotation around the double bond.

For thermal isomerization: Apply heat to the molecule. The energy provided by heat can overcome the activation barrier, allowing the molecule to transition from the cis to the trans configuration.

For photochemical isomerization: Expose the molecule to UV light. The light excites the π-electrons of the double bond to a higher energy state, creating a singlet or triplet excited state. This excited state allows free rotation around the double bond, leading to the trans configuration upon relaxation.

Ensure proper conditions: If using heat, maintain a controlled temperature to avoid decomposition. If using light, use a UV lamp with the appropriate wavelength to excite the π-electrons effectively.

Verified video answer for a similar problem:

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

Video duration:

10m

Play a video:

Was this helpful?

Key Concepts

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

Photochemical Reactions

Photochemical reactions are chemical processes that are initiated by the absorption of light. In organic chemistry, these reactions often involve the excitation of electrons, leading to the formation of reactive intermediates. Understanding how light energy can drive transformations is crucial for predicting the outcomes of reactions that rely on light as a catalyst.

Thermal Reactions

Thermal reactions are chemical reactions that occur due to the application of heat. Heat can provide the necessary energy to overcome activation barriers, allowing reactants to convert into products. In organic chemistry, recognizing how temperature influences reaction rates and mechanisms is essential for understanding transformations that occur solely through thermal energy.

Reaction Mechanisms

Reaction mechanisms describe the step-by-step sequence of elementary reactions that lead to the overall transformation of reactants into products. Understanding the mechanism is vital for predicting how heat or light can facilitate a reaction, as it reveals the intermediates and transition states involved. This knowledge helps chemists design conditions that favor desired pathways in organic transformations.