Covalent bond fission homolytic and heterolytic species stability electrophiles nucleophiles and common reaction types - Question Bank

1. Which type of cleavage is more common in polar protic solvents?
A) Homolytic cleavage
B) Heterolytic cleavage
C) Radical cleavage
D) Sigma cleavage
2. Which type of cleavage is more common in non-polar solvents?
A) Homolytic cleavage
B) Heterolytic cleavage
C) Ionic cleavage
D) Polar cleavage
3. The stability of a molecule or ion is inversely proportional to its:
A) Reactivity
B) Inertness
C) Bond strength
D) Electronegativity
4. A species that can act as both an electrophile and a nucleophile is:
A) Carbocation
B) Carbanion
C) Free radical
D) Carbonyl compound (e.g., RCHO)
5. Which of the following is a common type of reaction in organic chemistry?
A) Oxidative cleavage
B) Reductive cleavage
C) Addition
D) Decarboxylation
6. The stability of resonance structures is related to the:
A) Number of lone pairs
B) Number of pi electrons
C) Number of covalent bonds
D) Number of contributing structures and their energy
7. Which of the following is an example of a nucleophilic addition reaction?
A) Bromination of benzene
B) Addition of HCN to propanal
C) Chlorination of methane
D) Esterification
8. Which of the following is an example of an electrophilic aromatic substitution reaction?
A) Addition of HBr to ethene
B) Nitration of benzene
C) Saponification of an ester
D) Dehydration of ethanol
9. Which factor contributes to the stability of a free radical?
A) Presence of electronegative atoms
B) Delocalization of the unpaired electron
C) High positive charge density
D) Inductive withdrawal
10. A species with a negative charge and a complete octet is generally:
A) Stable
B) Unstable
C) Neutral
D) An electrophile
11. A species with a positive charge and a complete octet is generally:
A) Stable
B) Unstable
C) Neutral
D) A radical
12. The breaking of a bond where both electrons go to one atom is called:
A) Homolysis
B) Heterolysis
C) Photolysis
D) Thermolysis
13. Consider the reaction: R-OH + H+ → R-OH2+. What is the role of H+?
A) Nucleophile
B) Electrophile
C) Base
D) Reducing agent
14. Consider the reaction: CH3Cl + OH- → CH3OH + Cl-. What is the role of OH-?
A) Electrophile
B) Nucleophile
C) Leaving group
D) Catalyst
15. Which type of species is typically a Lewis base?
A) Carbocation
B) Electrophile
C) Nucleophile
D) Proton
16. Which type of species is typically a Lewis acid?
A) Nucleophile
B) Electrophile
C) Carbanion
D) Alkoxide
17. The stability order of tertiary, secondary, and primary carbanions is:
A) Primary > Secondary > Tertiary
B) Tertiary > Secondary > Primary
C) Secondary > Tertiary > Primary
D) Primary > Tertiary > Secondary
18. The stability order of tertiary, secondary, and primary carbocations is:
A) Primary > Secondary > Tertiary
B) Tertiary > Secondary > Primary
C) Secondary > Tertiary > Primary
D) Tertiary > Primary > Secondary
19. Which of the following is a characteristic feature of nucleophilic substitution reactions?
A) Attack by an electron-deficient species
B) Formation of carbocations
C) Attack by an electron-rich species
D) Loss of a leaving group
20. The reaction of methane with chlorine in the presence of sunlight is an example of:
A) Electrophilic substitution
B) Nucleophilic substitution
C) Free radical substitution
D) Addition reaction
21. A reaction where the carbon skeleton of a molecule is rearranged is called a:
A) Addition reaction
B) Substitution reaction
C) Elimination reaction
D) Rearrangement reaction
22. In a substitution reaction, one atom or group is replaced by another. This can be initiated by:
A) Nucleophiles only
B) Electrophiles only
C) Both nucleophiles and electrophiles
D) Free radicals
23. Which type of reaction involves the removal of atoms or groups from adjacent carbon atoms?
A) Addition
B) Substitution
C) Elimination
D) Rearrangement
24. The reaction of an alkyl halide with a strong base like KOH is typically an example of:
A) Electrophilic substitution
B) Nucleophilic substitution
C) Electrophilic addition
D) Elimination
25. The reaction of an alkene with Br2 in CCl4 is an example of which type of reaction?
A) Electrophilic addition
B) Nucleophilic addition
C) Free radical substitution
D) Electrophilic substitution
26. Which of the following is NOT a nucleophile?
A) H2O
B) NH3
C) SO3
D) Cl-
27. Which of the following is NOT an electrophile?
A) H+
B) AlCl3
C) R-OH
D) NO2+
28. A nucleophile can be:
A) An electron-deficient species
B) A species with a positive charge
C) A species with a lone pair of electrons
D) A Lewis acid
29. An electrophile can be:
A) An electron-rich species
B) A species with a vacant p-orbital
C) A species with a lone pair of electrons
D) An anion
30. Hyperconjugation is most significant in stabilizing:
A) Carbanions
B) Carbocations
C) Free radicals
D) Anions
31. Hyperconjugation is a stabilizing effect that involves:
A) Delocalization of sigma electrons from adjacent C-H or C-C bonds into an empty p-orbital
B) Delocalization of pi electrons
C) Donation of electron pairs
D) Withdrawal of electron density
32. Which of the following species is stabilized by resonance?
A) CH3+
B) CH3-
C) C6H5- (phenyl carbanion)
D) CH3•
33. Resonance stabilization generally leads to:
A) Decreased stability
B) Increased stability
C) No change in stability
D) Decreased reactivity
34. Which of the following free radicals is the most stable?
A) Methyl radical (CH3•)
B) Ethyl radical (CH3CH2•)
C) Isopropyl radical ((CH3)2CH•)
D) Vinyl radical (CH2=CH•)
35. Free radicals are stabilized by:
A) Electron-withdrawing groups
B) Electron-donating groups
C) Increasing positive charge
D) Decreasing number of unpaired electrons
36. Which of the following carbanions is the most stable?
A) Methyl carbanion (CH3-)
B) Ethyl carbanion (CH3CH2-)
C) Phenyl carbanion (C6H5-)
D) Propargyl carbanion (HC≡C-CH2-)
37. Stability of carbanions generally increases with:
A) Electron-donating inductive effect
B) Electron-withdrawing inductive effect
C) Decreasing number of alkyl groups
D) Increasing positive charge density
38. Which of the following carbocations is the most stable?
A) Methyl carbocation (CH3+)
B) Ethyl carbocation (CH3CH2+)
C) Isopropyl carbocation ((CH3)2CH+)
D) tert-Butyl carbocation ((CH3)3C+)
39. Stability of carbocations generally increases with:
A) Decreasing number of alkyl groups
B) Increasing positive charge density
C) Electron-donating inductive effect
D) Electron-withdrawing inductive effect
40. Consider the species R-Br. If treated with a Lewis acid like AlBr3, this bond might undergo heterolytic cleavage. What is likely formed?
A) R• and Br•
B) R- and Br+
C) R+ and Br-
D) R and Br
41. Consider the species R-Br. Under UV light, this bond undergoes homolytic cleavage. What is formed?
A) R+ and Br-
B) R- and Br+
C) R• and Br•
D) R and Br
42. Which of the following is a common nucleophile?
A) AlCl3
B) FeBr3
C) CN-
D) SO3
43. Which of the following is an example of an electrophile?
A) NH3
B) H2O
C) BF3
D) CH3COO-
44. A species that donates an electron pair to form a covalent bond is called a:
A) Electrophile
B) Nucleophile
C) Carbocation
D) Free radical
45. What term describes a species that accepts an electron pair to form a covalent bond?
A) Nucleophile
B) Electrophile
C) Carbanion
D) Radical
46. Which of the following is a characteristic of homolytic cleavage?
A) Formation of ions
B) Formation of free radicals
C) Requires polar solvents
D) Involves electronegativity difference
47. In heterolytic cleavage of a C-X bond (where X is more electronegative than C), which species will carry the negative charge?
A) The carbon atom
B) The atom X
C) Both carbon and X
D) Neither carbon nor X
48. Which type of bond cleavage results in the formation of two neutral radicals, each with an unpaired electron?
A) Homolytic cleavage
B) Heterolytic cleavage
C) Ionic cleavage
D) Polar cleavage
49. What type of bond cleavage occurs when a shared pair of electrons goes entirely to one of the bonded atoms?
A) Homolytic cleavage
B) Heterolytic cleavage
C) Sigma cleavage
D) Pi cleavage