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.
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- A. Substrate
- B. Nucleophile
- C. Both Options A and B are correct
- D. None of these options are correct
Explanation: In SN2 reactions, the rate of the reaction is directly proportional to the concentration of the nucleophile and the concentration of the…
Correct answer: Both Options A and B are correct- A. From the opposite side of the leaving group
- B. From the front of the leaving group
- C. From both sides
- D. None of these options are correct
Explanation: The correct answer is: From both sides. The nucleophile can attack the carbocation from either the front or the back side during an SN1…
Correct answer: From both sides- A. Water
- B. Benzene
- C. Carbon Tetrachloride
- D. Carbon disulphide
Explanation: SN1 reactions are favored by Polar prototic Solvents. These are polar solvents that are able to show hydrogen bonding.
Correct answer: Water- A. A carbocation
- B. A free radical
- C. A carbanion
- D. An intermediate complex
Explanation: In the first step of an SN1 reaction, the halide atom of the alkyl halide is removed, and the carbon atom becomes sp2 hybridized.
Correct answer: A carbocation- A. Sp2 to sp3
- B. Sp to sp2
- C. Sp3 to sp2
- D. Sp to sp3
Explanation: Normally, a carbon atom is sp3 hybridized. In the transition state of the SN2 mechanism, the carbon atom is sp2 hybridized due to its…
Correct answer: Sp3 to sp2- A. n-butane
- B. Propane
- C. Iso-butane
- D. Alcohol
Explanation: Explanation:Alkanes are produced when grignard reacts with:Water Ammonia AlcoholAs a result, n-butane will be produced in the above…
Correct answer: n-butane- A. Gets inverted
- B. Remains same
- C. Depends upon the carbon atom
- D. Depends upon the electronegativity of halide
Explanation: A is correct as during SN2 reaction, alkyl halide molecule gets inverted.B is incorrect as during SN2 reaction, alkyl halide doesnt stay…
Correct answer: Gets inverted- A. H2O at room temperature
- B. Ethanol, heat
- C. KOH in alcohol
- D. Dilute NaOH(aq) warm
Explanation: The given reaction is an example of alkaline hydrolysis or nucleophilic substitution reaction in which a halogen atom in an alkyl halide…
Correct answer: Dilute NaOH(aq) warm- A. NO2
- B. NH3
- C. NO2+
- D. NH4+
Explanation: A nucleophile is electron-rich species and donates electron pairs to electron-deficient species. Therefore, ammonia (NH3) is a nucleophile.
Correct answer: NH3- A. Breakage of covalent bond
- B. Formation of carbocation
- C. Transition state
- D. Attack of nucleophile
Explanation: The nucleophile has a negative / partially negative charge and it readily attacks the carbocation in SN1 reactions (which has a positive…
Correct answer: Attack of nucleophile- A. Nucleophiles
- B. Cations
- C. Free radicals
- D. Anions
Explanation: A nucleophile is a chemical species that donates an electron pair to form a chemical bond in relation to a reaction.
Correct answer: Nucleophiles- A. Primary carbocation
- B. Secondary carbocation
- C. Tertiary carbocation
- D. Methyl carbocation
Explanation: Methyl Carbocation (CH₃⁺)Structure: Only has one carbon atom, with no alkyl groups to stabilize the positive charge.Stability: Least…
Correct answer: Methyl carbocation- A. Primary>secondary>tertiary
- B. Tertiary>secondary>primary
- C. Secondary>primary>tertiary
- D. Primary>tertiary >secondary
Explanation: Tertiary > Secondary > Primary (Correct)Explanation: Tertiary carbocations are the most stable due to inductive and hyperconjugation…
Correct answer: Tertiary>secondary>primary- A. SN1
- B. SN2
- C. E1
- D. E2
Explanation: In organic chemistry, the reaction involving the simultaneous breaking of a carbon-halogen bond (-C-X) and the formation of a…
Correct answer: SN2- A. RX+H
- B. RH+HX
- C. 2RX+2Na-R-R+2NX
- D. R-X Mg-RMX
Explanation: The reaction of RX with KCN is a neucleophilic substitution reaction, as CN is a nucleophile that attacks the electrophilic carbocation.
Correct answer: RH+HX- A. nucleophiles
- B. electrophiles
- C. carbon ions
- D. carbonium ions
Explanation: Electrophiles: Electrophiles are electron-deficient species that accept a pair of electrons to form a new chemical bond.
Correct answer: electrophiles- A. Neopentyl system
- B. Tertiary compound with no branch
- C. Secondary halides
- D. Primary compound with no branch at β- carbon
Explanation: Primary compounds with no branching at the β-carbon, are generally the most suitable for SN2 reactions.
Correct answer: Primary compound with no branch at β- carbon- A. AICI3
- B. CN
- C. H3O
- D. BF3
Explanation: AlCl3, H3O+ and BF3 are electrophiles, while CN is a nucleophile.
Correct answer: CN- A. +CH3
- B. +CH3CH₂
- C. (CH3)2 +CH
- D. (CH3)3C+
Explanation: Option D represents a tertiary carbonium ion, which is much more stable than primary or secondary carbonium ions.
Correct answer: (CH3)3C+- A. NH3
- B. OH
- C. CN-
- D. Br2
Explanation: Br₂ is not a nucleophile because:No Significant Negative Charge:Nucleophiles are electron-rich species that donate electrons.Br₂ is a…
Correct answer: Br2