Nucleophilic substitution MCQ

MCQs on Nucleophilic Substitution Reactions (SN1 & SN2)

1. Which of the following undergoes SN1 reaction most readily?

A. CH3Cl B. (CH3)3CCl C. CH3CH2Cl D. C6H5Cl

2. The rate-determining step in SN1 reaction is:

A. Attack of nucleophile B. Loss of nucleophile C. Formation of carbocation D. Re-arrangement

3. Which factor increases SN2 reaction rate?

A. Bulky alkyl group B. Weak nucleophile C. Polar protic solvent D. Strong nucleophile

4. SN2 mechanism proceeds through:

A. Single-step backside attack B. Carbocation intermediate C. Free radical formation D. Two-step process

5. Which solvent favors SN1 reaction?

A. Acetone B. Water C. DMSO D. DMF

6. In SN2 reaction, the configuration of product is:

A. Inverted B. Retained C. Racemized D. Mixture

7. Which halide undergoes SN2 fastest?

A. (CH3)3CBr B. CH3CH2CH2Br C. CH3Br D. C6H5CH2Br

8. In SN1 reactions, the product is generally:

A. 100% inversion B. 100% retention C. No change D. Racemic mixture

9. Which order kinetics does SN2 follow?

A. Second order B. First order C. Zero order D. Third order

10. Which carbocation is most stable?

A. CH3+ B. (CH3)3C+ C. CH3CH2+ D. CH2=CH+

11. Which of the following favors SN2 over SN1?

A. Polar protic solvent B. Stable carbocation C. Primary alkyl halide D. Tertiary alkyl halide

12. Which is the best leaving group?

A. -OH B. -NH2 C. -OR D. -I

13. Which type of substrate undergoes fastest SN1 reaction?

A. Primary B. Tertiary C. Secondary D. Methyl

14. SN1 reaction rate depends on:

A. Concentration of substrate only B. Concentration of nucleophile only C. Both substrate and nucleophile D. None

15. Which nucleophile is strongest?

A. H2O B. CH3OH C. OH- D. HSO4-

16. Which halogen is best leaving group?

A. F B. I C. Cl D. Br

17. In SN2 reaction, transition state contains:

A. Both nucleophile and leaving group partially bonded B. Only carbocation C. Only nucleophile D. Free radical

18. Allyl halides undergo SN1 fast because:

A. Steric hindrance B. Weak bond C. Strong nucleophile D. Resonance stabilized carbocation

19. Which one is an aprotic solvent?

A. H2O B. CH3OH C. Acetone D. NH3

20. SN1 is favored by:

A. Polar protic solvents B. Polar aprotic solvents C. Non-polar solvents D. Gaseous medium