NEET UG - Covalent bond fission homolytic and heterolytic species stability electrophiles nucleophiles and common reaction types Online Test (MCQ Quiz)

1. 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

2. 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

3. 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

4. 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

5. What term describes a species that accepts an electron pair to form a covalent bond?

A) Nucleophile B) Electrophile C) Carbanion D) Radical

6. A species that donates an electron pair to form a covalent bond is called a:

A) Electrophile B) Nucleophile C) Carbocation D) Free radical

7. Which of the following is an example of an electrophile?

A) NH3 B) H2O C) BF3 D) CH3COO-

8. Which of the following is a common nucleophile?

A) AlCl3 B) FeBr3 C) CN- D) SO3

9. 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

10. 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

11. 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

12. 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+)

13. 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

14. 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-)

15. Free radicals are stabilized by:

A) Electron-withdrawing groups B) Electron-donating groups C) Increasing positive charge D) Decreasing number of unpaired electrons

16. 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•)

17. Resonance stabilization generally leads to:

A) Decreased stability B) Increased stability C) No change in stability D) Decreased reactivity

18. Which of the following species is stabilized by resonance?

A) CH3+ B) CH3- C) C6H5- (phenyl carbanion) D) CH3•

19. 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

20. Hyperconjugation is most significant in stabilizing:

A) Carbanions B) Carbocations C) Free radicals D) Anions

21. 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

22. 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

23. Which of the following is NOT an electrophile?

A) H+ B) AlCl3 C) R-OH D) NO2+

24. Which of the following is NOT a nucleophile?

A) H2O B) NH3 C) SO3 D) Cl-

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. 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

27. Which type of reaction involves the removal of atoms or groups from adjacent carbon atoms?

A) Addition B) Substitution C) Elimination D) Rearrangement

28. 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

29. 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

30. 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

31. 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

32. 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

33. 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

34. Which type of species is typically a Lewis acid?

A) Nucleophile B) Electrophile C) Carbanion D) Alkoxide

35. Which type of species is typically a Lewis base?

A) Carbocation B) Electrophile C) Nucleophile D) Proton

36. Consider the reaction: CH3Cl + OH- → CH3OH + Cl-. What is the role of OH-?

A) Electrophile B) Nucleophile C) Leaving group D) Catalyst

37. Consider the reaction: R-OH + H+ → R-OH2+. What is the role of H+?

A) Nucleophile B) Electrophile C) Base D) Reducing agent

38. The breaking of a bond where both electrons go to one atom is called:

A) Homolysis B) Heterolysis C) Photolysis D) Thermolysis

39. A species with a positive charge and a complete octet is generally:

A) Stable B) Unstable C) Neutral D) A radical

40. A species with a negative charge and a complete octet is generally:

A) Stable B) Unstable C) Neutral D) An electrophile

41. 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

42. 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

43. 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

44. 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

45. Which of the following is a common type of reaction in organic chemistry?

A) Oxidative cleavage B) Reductive cleavage C) Addition D) Decarboxylation

46. 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)

47. The stability of a molecule or ion is inversely proportional to its:

A) Reactivity B) Inertness C) Bond strength D) Electronegativity

48. Which type of cleavage is more common in non-polar solvents?

A) Homolytic cleavage B) Heterolytic cleavage C) Ionic cleavage D) Polar cleavage

49. Which type of cleavage is more common in polar protic solvents?

A) Homolytic cleavage B) Heterolytic cleavage C) Radical cleavage D) Sigma cleavage

Covalent bond fission homolytic and heterolytic species stability electrophiles nucleophiles and common reaction types - Online Test

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