Reactive intermediates: carbocations, carbanions, free radicals, carbenes and nitrenes - One Line Questions

1. Which of the following is an example of a tertiary carbocation? — (CH3)3C+
2. The Hofmann rearrangement is initiated by the formation of: — A nitrene
3. The Fischer indole synthesis involves the cyclization of a phenylhydrazone, which can be thought of as involving: — A nitrene intermediate
4. Free radicals are characterized by the presence of: — An unpaired electron
5. Dichlorocarbene (:CCl2) is an example of: — A singlet carbene
6. A carbene with two identical substituents on the carbon atom is called: — A symmetrical carbene
7. Carbanions are typically formed by the abstraction of which type of hydrogen atom? — Acidic hydrogen
8. The Kolbe electrolysis of carboxylic acids produces: — Alkanes
9. The Wolff rearrangement converts an alpha-diazoketone into: — An ester or amide
10. Which reaction involves the generation of a free radical from an azo compound? — AIBN decomposition
11. Which carbocation is least stable? — Methyl carbocation
12. Which of the following is an electrophile? — Carbocation
13. Which intermediate is planar and has an empty p orbital? — Carbocation
14. The addition of halogens to alkenes often proceeds via a: — Carbocation intermediate
15. The Curtius rearrangement involves the formation of which reactive intermediate? — Nitrene
16. Which of the following is a strong nucleophile and a strong base? — Carbanion
17. Which reactive intermediate is involved in the Wurtz reaction? — Free radical
18. In organic synthesis, which intermediate is often generated using organometallic reagents? — Carbanion
19. The nucleophilic addition to carbonyl compounds often involves the formation of: — Carbanion
20. Which reactive intermediate is characterized by a carbon atom with a lone pair and two bonds? — Carbanion
21. Which reactive intermediate has a pyramidal geometry at the central carbon atom? — Carbanion
22. The Hunt-Shorter rearrangement is a type of: — Free radical rearrangement
23. The Tiffeneau-Demjanov rearrangement is a type of: — Carbocation rearrangement
24. Nitrenes are the nitrogen analogues of: — Carbenes
25. Homolytic cleavage of a covalent bond leads to the formation of: — Free radicals
26. The stability order of free radicals is generally similar to that of: — Carbocations
27. Which of the following would most readily undergo homolytic cleavage? — CH3-CH3
28. Which of the following is an example of a carbanion? — CH3-
29. Which of the following is a triplet carbene? — Methylene (CH2)
30. The stability of carbanions decreases with the introduction of: — Electron-donating groups
31. The stability of a carbanion is increased by: — Electron-withdrawing groups
32. The term 'radical scavenger' refers to a substance that: — Reacts with and neutralizes free radicals
33. The Schmidt reaction involves the reaction of a ketone or aldehyde with: — Hydrazoic acid
34. The geometry around the carbon atom in a carbene is typically: — Trigonal planar
35. Which of the following is a resonance-stabilized carbanion? — Acetylide anion
36. Which of the following is the most stable carbocation? — tert-Butyl carbocation
37. Which of the following is a resonance-stabilized carbocation? — Allyl carbocation
38. Which of the following is a common method for generating free radicals? — Homolysis induced by heat or light
39. The insertion reactions of carbenes into C-H bonds are characteristic of: — Singlet carbenes
40. The hybridization of the carbon atom in a methyl carbocation (CH3+) is: — sp2
41. The carbon atom in a carbanion is typically hybridized: — sp3
42. Which reagent is commonly used to generate free radicals from peroxides? — Heat or light
43. The stability of carbanions follows the order: — tert-Butyl < Isopropyl < Ethyl < Methyl
44. The stability order of carbocations from least to most stable is: — Methyl < Ethyl < Isopropyl < tert-Butyl
45. Which species is resonance stabilized? — Allyl carbocation
46. The negative charge in a carbanion is localized on: — The carbon atom
47. Which statement about carbocations is FALSE? — They are hybridized sp3.
48. Which statement about triplet carbenes is correct? — They have unpaired electrons with parallel spins.
49. Carbenes are neutral molecules with a carbon atom having: — Two bonding electrons and a lone pair
50. Singlet carbenes have their two non-bonding electrons in: — The same orbital with opposite spins
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