Pericyclic reactions, electrocyclisation, cycloaddition and sigmatropic rearrangements - One Line Questions

1. Which type of sigmatropic rearrangement involves the migration of a hydrogen atom? — All of the above
2. Which type of pericyclic reaction involves a 'two-atom' component adding to a 'four-atom' pi system? — [4+2] Cycloaddition
3. 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? — [n,m]-sigmatropic
4. What is the minimum number of atoms that must rearrange in a sigmatropic rearrangement? — 2
5. The term 'homo-sigmatropic rearrangement' refers to a sigmatropic rearrangement where the migration occurs across how many atoms, including the migrating group? — 4
6. What is the minimum number of atoms required to form a cyclic system in an electrocyclisation reaction? — 3
7. Which type of electrocyclisation involves the formation of a three-membered ring from a conjugated system? — 2 pi electron system
8. A [1,5]-sigmatropic rearrangement involves the migration of a sigma bond and a pi bond across how many atoms? — 5
9. Thermal electrocyclisation of a 4 pi electron system typically results in the formation of a ring with how many members? — 4
10. Photochemical electrocyclisation of a 4 pi electron system typically results in the formation of a ring with how many members? — 5
11. The thermal electrocyclisation of a 1,3,5-hexatriene (6 pi electrons) leads to the formation of which ring size? — 4-membered ring
12. In a [4+2] cycloaddition reaction, how many pi electrons are involved in the transition state? — 6
13. 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? — 6
14. Which of the following is a thermal electrocyclisation that results in a 5-membered ring? — 6 pi electron system
15. The Wessely-Moser rearrangement is an example of a sigmatropic rearrangement often seen in which class of compounds? — Steroids
16. The Claisen rearrangement is a specific type of [3,3]-sigmatropic rearrangement involving which functional groups? — Allylic vinyl ethers
17. Which term describes the face selectivity in a pericyclic reaction where both components react on the same face? — Suprafacial
18. Which of the following is a characteristic of the suprafacial approach in cycloaddition reactions? — Bond formation on the same face of the pi system
19. In the context of cycloadditions, what does the term 'antarafacial' refer to? — Bond formation on opposite faces of both reacting components
20. The stereochemical outcome of a photochemical electrocyclisation of a 6 pi electron system is typically: — Disrotatory
21. What is the characteristic motion for a thermal electrocyclisation of a 6 pi electron system according to the Woodward-Hoffmann rules? — Disrotatory opening and disrotatory closing
22. A [3,3]-sigmatropic rearrangement is also known as which reaction? — Cope rearrangement
23. Which of the following is an example of a [1,5]-sigmatropic rearrangement? — Prototropic shift
24. Which of the following is a [2,3]-sigmatropic rearrangement? — Wittig rearrangement
25. Which term describes the movement of atoms or groups across a pi system in a concerted manner? — Sigmatropic rearrangement
26. Which type of pericyclic reaction involves the simultaneous formation of two new sigma bonds from a single molecule? — Cheletropic reaction
27. Which of the following is NOT a pericyclic reaction? — SN2 reaction
28. In a [2+2] cycloaddition reaction, what is the typical stereochemical outcome under thermal conditions? — Disrotatory
29. According to the Woodward-Hoffmann rules, a thermal electrocyclisation of a 6 pi electron system proceeds via which motion? — Disrotatory
30. Photochemical [2+2] cycloaddition reactions typically proceed via which motion? — Suprafacial
31. 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? — Conrotatory
32. In a [2+2] cycloaddition, the photochemical reaction typically favors which motion? — Disrotatory
33. The photochemical [4+2] cycloaddition reaction typically proceeds via which motion? — Conrotatory
34. According to the Woodward-Hoffmann rules, a photochemical electrocyclisation of a 4 pi electron system proceeds via which motion? — Conrotatory
35. Which type of pericyclic reaction involves the formation of a new cyclic system from two or more unsaturated molecules? — Cycloaddition
36. The Diels-Alder reaction is a classic example of which type of pericyclic reaction? — [4+2] Cycloaddition
37. The Moebius strip analogy is used to explain the orbital symmetry rules for which type of pericyclic reaction? — Sigmatropic rearrangement
38. The thermal opening of a cyclobutene (4 pi electron system) is an example of which type of pericyclic reaction? — Electrocyclisation
39. 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? — Both A and C
40. What is the primary driving force for many pericyclic reactions? — Preservation of orbital symmetry
41. 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? — HOMO(diene)/LUMO(dienophile)
42. Which of the following is a feature of cheletropic reactions? — Involves a single atom or group coordinating to a pi system
43. Which term describes the movement of a sigma bond across a pi system in a sigmatropic rearrangement? — Migration
44. Which of the following is a characteristic of a [1,2]-sigmatropic rearrangement? — Migration of a sigma bond over 2 atoms
45. The Woodward-Hoffmann rules predict the stereochemistry of pericyclic reactions based on which principle? —
46. Which of the following is a key feature of the Woodward-Hoffmann rules? — Relates the symmetry of molecular orbitals in the ground and excited states to the reaction pathway
47. Which of the following is a requirement for a concerted mechanism in pericyclic reactions? — Continuous overlap of orbitals
48. Which of the following is a characteristic feature of pericyclic reactions? — Concerted mechanism
49. In a [4+2] cycloaddition, the diene must be able to adopt which conformation for the reaction to occur? — S-cis
50. Which term describes the simultaneous formation and breaking of sigma and pi bonds in a pericyclic reaction? — Concerted process
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