Inductive Effect - UNSOLVED PRACTICE SET
Chapter: Organic Chemistry Basic Principles | Topic: Inductive Effect
INDUCTIVE EFFECT - UNSOLVED PRACTICE SET
Topic: Inductive Effect
Multiple Choice Questions
Q1. The inductive effect is:
- A permanent effect involving delocalisation of π electrons
- A permanent effect involving displacement of σ electrons
- A temporary effect involving displacement of σ electrons
- A temporary effect involving delocalisation of π electrons
Q2. Which of the following groups shows a –I (negative inductive) effect?
- –CH₃
- –C₂H₅
- –NO₂
- –CH(CH₃)₂
Q3. The order of –I effect among halogens is:
- F > Cl > Br > I
- I > Br > Cl > F
- Cl > F > Br > I
- Br > Cl > F > I
Q4. Which of the following groups shows a +I (positive inductive) effect?
- –CN
- –NO₂
- –CH₃
- –COOH
Q5. The inductive effect:
- Increases with distance and does not decrease
- Decreases with distance and becomes negligible after the third carbon atom
- Remains constant throughout the carbon chain
- Is zero for all carbon atoms
Q6. In CH₃–CH₂–CH₂–Cl, the carbon atom attached to chlorine will have:
- Excess electron density
- Deficient electron density
- No change in electron density
- Equal sharing of electrons
Short Answer Questions
Q7. Define inductive effect. Differentiate between +I effect and –I effect with one example of each.
Q8. Arrange the following groups in decreasing order of –I effect and explain your reasoning:
–NO₂, –F, –Cl, –OH, –CH₃
Q9. Explain why the acidic strength of chloroacetic acid is greater than that of acetic acid.
Q10. Why is the dipole moment of CH₃Cl greater than that of CH₃F, even though fluorine is more electronegative than chlorine?
Q11. Your teacher asks why trichloroacetic acid (CCl₃COOH) is a stronger acid than acetic acid (CH₃COOH). Explain using the concept of the inductive effect.
Q12. How does the inductive effect explain the stability of carbocations? Arrange the following carbocations in order of increasing stability and give reasons:
CH₃⁺, CH₃CH₂⁺, (CH₃)₂CH⁺, (CH₃)₃C⁺
Long Answer Questions
Q13. Discuss the inductive effect in detail:
(a) Definition and nature of the inductive effect
(b) +I effect — electron-donating groups and examples
(c) –I effect — electron-withdrawing groups and examples
(d) How the inductive effect decreases with distance along the carbon chain
(e) The role of inductive effect in determining acidic and basic strength
Q14. Explain how the inductive effect influences:
(a) The acidic strength of carboxylic acids (compare formic acid, acetic acid, chloroacetic acid, and trichloroacetic acid)
(b) The basic strength of amines (compare methylamine, dimethylamine, and trimethylamine)
(c) The stability of carbocations and carbanions
Give reasons for each trend with relevant structures.
Q15. The inductive effect is crucial in understanding drug action and material properties. Discuss:
(a) How the –I effect of fluorine in fluorinated drugs enhances their metabolic stability
(b) Why chloroquine (an antimalarial drug) contains a chlorine atom and how the inductive effect affects its biological activity
(c) How the +I effect of alkyl groups affects the boiling points of alcohols and amines
(d) The role of inductive effects in designing pesticides used in Indian agriculture
Numerical / Application-Based Problems
Q16. The pKa values of the following carboxylic acids are given:
Acetic acid (CH₃COOH): 4.76
Chloroacetic acid (ClCH₂COOH): 2.86
Dichloroacetic acid (Cl₂CHCOOH): 1.35
Trichloroacetic acid (Cl₃CCOOH): 0.70
(a) Arrange these acids in order of increasing acidic strength.
(b) Calculate the ratio of [H⁺] concentrations for trichloroacetic acid and acetic acid.
(c) Explain how the increasing number of chlorine atoms affects the acidity using the inductive effect.
Q17. The dipole moments of CH₃Cl, CH₂Cl₂, and CHCl₃ are 1.87 D, 1.54 D, and 1.15 D respectively.
(a) Explain why CH₃Cl has the highest dipole moment despite having only one chlorine atom.
(b) Explain why the dipole moment decreases as more chlorine atoms are added.
(c) Predict whether CCl₄ would have a dipole moment and explain your reasoning.
Q18. A pharmaceutical company in Hyderabad is comparing two drug candidates:
Drug A: C₆H₅–CH₂–NH₂ (benzylamine)
Drug B: C₆H₅–CH₂–CF₂–NH₂ (fluorinated benzylamine)
(a) Identify which drug would have a more basic –NH₂ group and explain using the inductive effect.
(b) If the pKb of Drug A is 4.67, predict whether the pKb of Drug B would be higher or lower.
(c) Explain how this difference in basicity might affect the drug's absorption in the human body.