Types of Reagents - Electrophile Nucleophile - UNSOLVED PRACTICE SET

Q7. Define electrophile and nucleophile. Give two examples of each.

Q8. Why is BF₃ an electrophile but NH₃ a nucleophile? Explain with reference to their electronic structures.

Q9. Classify the following as electrophiles or nucleophiles:

(a) H₂O

(b) CN⁻

(c) R–X (alkyl halide)

(d) R–O⁻ (alkoxide ion)

Q10. Explain why carbocations are electrophiles while carbanions are nucleophiles.

Q11. Your teacher adds bromine water to an alkene and the colour disappears. Identify the electrophile and nucleophile in this reaction and explain their roles.

Q12. Why is the hydroxide ion (OH⁻) a stronger nucleophile than water (H₂O)? Explain in terms of charge and electron availability.

Q13. Discuss electrophiles and nucleophiles in detail:

(a) Definition and characteristics of electrophiles

(b) Types of electrophiles: positively charged (H⁺, Cl⁺, NO₂⁺) and neutral with empty orbitals (BF₃, AlCl₃, SO₃)

(c) Definition and characteristics of nucleophiles

(d) Types of nucleophiles: negatively charged (OH⁻, CN⁻, R⁻) and neutral with lone pairs (H₂O, NH₃, ROH)

(e) Ambident nucleophiles (e.g., CN⁻ can attack through C or N)

Q14. Explain the factors that affect nucleophilicity:

(a) Charge — why negatively charged species are stronger nucleophiles

(b) Electronegativity — why basicity and nucleophilicity may differ

(c) Solvent effects — why polar protic solvents decrease nucleophilicity of small anions

(d) Steric hindrance — why bulky groups reduce nucleophilicity

Give examples to illustrate each factor.

Q15. The concepts of electrophiles and nucleophiles are fundamental to drug design and biochemistry. Discuss:

(a) How aspirin (acetylsalicylic acid) works by acting as an electrophile that acetylates an enzyme

(b) Why mustard gas (used in chemical warfare) is a powerful electrophile that damages DNA

(c) How nucleophilic substitution reactions are used in the synthesis of antibiotics in Indian pharmaceutical companies

(d) The role of nucleophiles in the mechanism of action of organophosphate pesticides

Q16. Consider the following species and classify them as electrophiles (E) or nucleophiles (N):

H⁺, OH⁻, Br⁻, AlCl₃, NH₃, NO₂⁺, CN⁻, BF₃, H₂O, CH₃⁺

(a) Create two lists: one for electrophiles and one for nucleophiles.

(b) For each electrophile, identify the atom that accepts the electron pair.

(c) For each nucleophile, identify the atom that donates the electron pair.

Q17. In the reaction between CH₃Br and NH₃:

(a) Identify the electrophile and nucleophile.

(b) Draw the curved arrow mechanism showing electron movement.

(c) Predict the product and identify the type of reaction.

(d) If NH₃ is replaced by (CH₃)₃N (trimethylamine), would the reaction be faster or slower? Explain using steric hindrance.

Q18. A pharmaceutical company in Hyderabad is synthesising a drug using the reaction:

R–Cl + NaCN → R–CN + NaCl

(a) Identify the electrophile and nucleophile in this reaction.

(b) Explain why CN⁻ is an ambident nucleophile and predict whether the major product would be R–CN or R–NC.

(c) If the solvent is changed from ethanol (polar protic) to DMSO (polar aprotic), predict how the reaction rate would change and explain why.