Free Nucleophilic Substitution MCQs with Answers
65 Nucleophilic Substitution MCQs from Chemistry, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Nucleophilic substitution replaces a leaving group in an alkyl halide when an electron-rich nucleophile attacks the carbon atom. The topic compares SN1 and SN2 mechanisms, including reaction conditions, substrate structure, solvent effects, nucleophile strength, carbocation formation and stereochemical changes, and distinguishes substitution from elimination.
Last updated
65 questions · page 1 of 4
- A. R-F greater than R-Cl greater than R-Br greater than R-I
- B. R-I greater than R-Br greater than R-Cl greater than R-F
- C. all four react at the same rate
- D. R-Cl greater than R-I greater than R-Br greater than R-F
Explanation: Reactivity is governed by the strength of the carbon to halogen bond, and that bond weakens down the group as the halogen gets larger, so…
Correct answer: R-I greater than R-Br greater than R-Cl greater than R-F- A. ethene
- B. ethanoic acid
- C. ethane
- D. ethanol
Explanation: In aqueous solution the hydroxide ion acts as a nucleophile, replacing the bromine to give ethanol in a substitution reaction.
Correct answer: ethanol- A. a two step mechanism through a carbocation
- B. first order kinetics involving only the alkyl halide
- C. a single step in which the nucleophile attacks as the leaving group departs, with second order kinetics
- D. the formation of a free radical intermediate
Explanation: The nucleophile approaches from the side opposite the leaving group and bond forming and bond breaking occur together through a five…
Correct answer: a single step in which the nucleophile attacks as the leaving group departs, with second order kinetics- A. the tertiary carbocation formed is relatively stable and the carbon is too hindered for back side attack
- B. tertiary halides have the weakest carbon to halogen bond
- C. tertiary carbon atoms carry a full positive charge already
- D. the nucleophile is always weak
Explanation: Three electron releasing alkyl groups spread the positive charge and stabilise the carbocation, so the slow ionisation step becomes…
Correct answer: the tertiary carbocation formed is relatively stable and the carbon is too hindered for back side attack- A. both the alkyl halide and the nucleophile
- B. the alkyl halide only
- C. the nucleophile only
- D. the solvent only
Explanation: The slow, rate determining step is the ionisation of the alkyl halide into a carbocation and a halide ion, and the nucleophile is not…
Correct answer: the alkyl halide only- A. ethanol
- B. ethylamine
- C. ethanenitrile
- D. ethane
Explanation: Ammonia has a lone pair on nitrogen and acts as a nucleophile, displacing bromide to give ethylamine, though the product is itself…
Correct answer: ethylamine- A. shortens the carbon chain by one atom
- B. produces an alkene
- C. lengthens the carbon chain by one carbon atom
- D. removes the halogen without adding anything
Explanation: The cyanide ion substitutes for the halogen, so the nitrile formed has one more carbon than the starting halide, and that nitrile can then…
Correct answer: lengthens the carbon chain by one carbon atom- A. sodium metal in dry ether
- B. magnesium in dry ether
- C. zinc in aqueous solution
- D. copper in ethanol
Explanation: Magnesium inserts itself into the carbon to halogen bond to give an alkylmagnesium halide, and the ether must be perfectly dry because…
Correct answer: magnesium in dry ether- A. CH3Br
- B. CH3CH2Br
- C. (CH3)2CHBr
- D. (CH3)3CBr
Explanation: SN1 rates follow the stability of the carbocation formed, and that increases from primary through secondary to tertiary because each alkyl…
Correct answer: (CH3)3CBr- A. inverted, because the nucleophile attacks from the side opposite the leaving group
- B. retained completely
- C. randomised, giving a racemic mixture
- D. unchanged because no bond is broken
Explanation: Back side attack turns the three remaining groups inside out like an umbrella in the wind, so an optically active substrate gives a…
Correct answer: inverted, because the nucleophile attacks from the side opposite the leaving group- A. measure the boiling point of the halide
- B. convert the halide into an alkene
- C. prepare a Grignard reagent
- D. compare the relative rates at which different carbon to halogen bonds break
Explanation: The halide ion must be released before it can precipitate with silver, so the speed at which the precipitate appears reflects how easily…
Correct answer: compare the relative rates at which different carbon to halogen bonds break- A. Flouride ion
- B. Bromide ion
- C. Chloride ion
- D. Iodide ion
Explanation: In a polar aprotic solvent, fluoride ion is strongly nucleophilic because it is not extensively hydrogen-bonded or solvated by the…
Correct answer: Flouride ion- A. Inversion
- B. Retention
- C. Recemic Mixture
- D. Stereospecific
Explanation: An SN1 reaction forms a planar carbocation intermediate, so the nucleophile can attack from either side and usually gives a racemic…
Correct answer: Recemic Mixture- A. Glycols
- B. Vicinal dihalides
- C. Geminal dihalides
- D. Diols
Explanation: A compound with two halogen atoms attached to adjacent carbon atoms contains a vicinal dihalide, with the substituents on neighbouring…
Correct answer: Vicinal dihalides- A. Water
- B. Hexane
- C. Dimethylflormamide
- D. Ethanol
Explanation: SN2 reactions are fastest in polar aprotic solvents because these solvents dissolve ions without strongly solvating and slowing the…
Correct answer: Dimethylflormamide- A. CH3Br
- B. CH3CH2Br
- C. CH3CH2CH2Br
- D. (CH3)3CBr
Explanation: SN1 reactions proceed through a carbocation, so the substrate that forms the most stable carbocation reacts most readily.
Correct answer: (CH3)3CBr- A. Nucleophilic substitution
- B. Nucleophilic addition
- C. Elimination
- D. both A & C
Explanation: The carbon-halogen bond in an alkyl halide can undergo nucleophilic substitution, while a base can remove a hydrogen and cause…
Correct answer: both A & C- A. they have an electrophilic carbon
- B. they have an electrophilic carbon & a good leaving group
- C. they have an electrophilic carbon & a bad leaving group
- D. they have a nucleophilic carbon & a good leaving group
Explanation: The carbon bonded to halogen is electron-deficient because the halogen withdraws electron density, making that carbon electrophilic.
Correct answer: they have an electrophilic carbon & a good leaving group- A. E1 + E2
- B. E2 + SN2
- C. E1 and SN1
- D. SN1 and SN2
Explanation: E1 and SN1 reactions both begin with ionization of the carbon-halogen bond to form a carbocation, which is the slow, rate-determining…
Correct answer: E1 and SN1- A. primary alkyl halide
- B. secondary alkyl halide
- C. tertiary alkyl halide
- D. all
Explanation: SN2 reactions require backside attack by the nucleophile, so steric hindrance must be small; primary alkyl halides provide the least…
Correct answer: primary alkyl halideNucleophilic Substitution MCQs: common questions
Are these Nucleophilic Substitution MCQs free?
Yes. All Nucleophilic Substitution MCQs from Chemistry are free on TestUstad, with unlimited attempts and no account needed. Nothing on this page is a sample or a trial.
How many Nucleophilic Substitution MCQs are on this page?
There are 65 Nucleophilic Substitution MCQs in the Chemistry bank, shown 20 to a page with the correct answer and an explanation on each.
Does every Nucleophilic Substitution MCQ have an explanation?
Yes. Each Nucleophilic Substitution question shows the correct option and a written explanation of why it is correct, so a wrong answer teaches you something rather than just being marked wrong.
Can I take a timed Nucleophilic Substitution test?
Yes. The practice button on this page starts a free Nucleophilic Substitution test drawn from the Chemistry bank. It marks each answer instantly, gives you a score at the end, and can be retaken as many times as you like.