Pericyclic reactions, electrocyclisation, cycloaddition and sigmatropic rearrangements - Question Bank
1. Which of the following is a [2,3]-sigmatropic rearrangement?
2. The thermal opening of a cyclobutene (4 pi electron system) is an example of which type of pericyclic reaction?
3. Which term describes the face selectivity in a pericyclic reaction where both components react on the same face?
4. Which of the following is a feature of cheletropic reactions?
5. According to the Woodward-Hoffmann rules, a photochemical electrocyclisation of a 4 pi electron system proceeds via which motion?
6. The Wessely-Moser rearrangement is an example of a sigmatropic rearrangement often seen in which class of compounds?
7. Which of the following is a characteristic of a [1,2]-sigmatropic rearrangement?
8. The photochemical [4+2] cycloaddition reaction typically proceeds via which motion?
9. Which type of pericyclic reaction involves a 'two-atom' component adding to a 'four-atom' pi system?
10. What is the minimum number of atoms required to form a cyclic system in an electrocyclisation reaction?
11. In the Diels-Alder reaction, the regioselectivity is often explained by considering the interaction between the HOMO of one component and the LUMO of the other. Which is typically the HOMO/LUMO pairing?
12. Which of the following is a key feature of the Woodward-Hoffmann rules?
13. The term 'homo-sigmatropic rearrangement' refers to a sigmatropic rearrangement where the migration occurs across how many atoms, including the migrating group?
14. Which of the following is a thermal electrocyclisation that results in a 5-membered ring?
15. In the context of cycloadditions, what does the term 'antarafacial' refer to?
16. What is the primary driving force for many pericyclic reactions?
17. Which type of pericyclic reaction involves the simultaneous formation of two new sigma bonds from a single molecule?
18. The stereochemical outcome of a photochemical electrocyclisation of a 6 pi electron system is typically:
19. Which of the following is an example of a [1,5]-sigmatropic rearrangement?
20. In a [4+2] cycloaddition, the diene must be able to adopt which conformation for the reaction to occur?
21. Which term describes the movement of atoms or groups across a pi system in a concerted manner?
22. The thermal electrocyclisation of a 1,3,5-hexatriene (6 pi electrons) leads to the formation of which ring size?
23. Which of the following is a characteristic of the suprafacial approach in cycloaddition reactions?
24. The Moebius strip analogy is used to explain the orbital symmetry rules for which type of pericyclic reaction?
25. What is the designation for a sigmatropic rearrangement where a substituent migrates across a pi system, and the sigma bond breaks and forms between atoms separated by 'n' atoms in the pi system?
26. In a [2+2] cycloaddition, the photochemical reaction typically favors which motion?
27. Which term describes the simultaneous formation and breaking of sigma and pi bonds in a pericyclic reaction?
28. The stereochemistry of photochemical reactions is often governed by excited states. For a photochemical electrocyclisation of a 4 pi electron system, which motion is favored?
29. Which type of sigmatropic rearrangement involves the migration of a hydrogen atom?
30. What is the characteristic motion for a thermal electrocyclisation of a 6 pi electron system according to the Woodward-Hoffmann rules?
31. In a [4+2] cycloaddition, the diene is considered the '4 pi electron' component and the dienophile is the '2 pi electron' component. What is the total number of pi electrons in the transition state?
32. Which of the following is NOT a pericyclic reaction?
33. The Ene reaction is a type of pericyclic reaction that involves the transfer of a hydrogen atom and the formation of a new sigma bond. What is another key feature?
34. Photochemical [2+2] cycloaddition reactions typically proceed via which motion?
35. Which term describes the movement of a sigma bond across a pi system in a sigmatropic rearrangement?
36. The Claisen rearrangement is a specific type of [3,3]-sigmatropic rearrangement involving which functional groups?
37. A [3,3]-sigmatropic rearrangement is also known as which reaction?
38. According to the Woodward-Hoffmann rules, a thermal electrocyclisation of a 6 pi electron system proceeds via which motion?
39. Which of the following is a requirement for a concerted mechanism in pericyclic reactions?
40. In a [2+2] cycloaddition reaction, what is the typical stereochemical outcome under thermal conditions?
41. The Diels-Alder reaction is a classic example of which type of pericyclic reaction?
42. Photochemical electrocyclisation of a 4 pi electron system typically results in the formation of a ring with how many members?
43. Thermal electrocyclisation of a 4 pi electron system typically results in the formation of a ring with how many members?
44. Which type of electrocyclisation involves the formation of a three-membered ring from a conjugated system?
45. A [1,5]-sigmatropic rearrangement involves the migration of a sigma bond and a pi bond across how many atoms?
46. What is the minimum number of atoms that must rearrange in a sigmatropic rearrangement?
47. The Woodward-Hoffmann rules predict the stereochemistry of pericyclic reactions based on which principle?
48. Which of the following is a characteristic feature of pericyclic reactions?
49. In a [4+2] cycloaddition reaction, how many pi electrons are involved in the transition state?
50. Which type of pericyclic reaction involves the formation of a new cyclic system from two or more unsaturated molecules?