Free Nucleophilic Addition Reactions MCQs with Answers
35 Nucleophilic Addition Reactions 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 addition occurs at the polar carbonyl group of aldehydes and ketones, where a nucleophile attacks the electron-deficient carbon atom. Reactions with hydrogen cyanide, sodium bisulfite, alcohols and Grignard reagents are explained through tetrahedral intermediates, acid or base catalysis, and the different reactivity of aldehydes and ketones.
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- A. ethanoic acid
- B. 2-hydroxypropanenitrile
- C. ethanol
- D. propanone
Explanation: The cyanide ion attacks the carbonyl carbon and the resulting alkoxide picks up a proton, giving a hydroxynitrile with one more carbon…
Correct answer: 2-hydroxypropanenitrile- A. a primary alcohol
- B. a carboxylic acid
- C. a secondary alcohol
- D. an alkane
Explanation: The hydride ion adds to the carbonyl carbon, which then carries two alkyl groups and a hydroxyl, so the product is a secondary alcohol.
Correct answer: a secondary alcohol- A. measuring the pH of the compound
- B. separating and purifying the carbonyl compound, since the adduct can be decomposed to regenerate it
- C. converting the compound into an alkane
- D. detecting the presence of a benzene ring
Explanation: The bisulphite adduct crystallises out and can be filtered off, and treating it with dilute acid or alkali releases the original aldehyde…
Correct answer: separating and purifying the carbonyl compound, since the adduct can be decomposed to regenerate it- A. sp3 to sp2
- B. sp to sp2
- C. sp2 to sp3
- D. sp3 to sp
Explanation: The carbonyl carbon starts as trigonal planar sp2 with a bond angle of 120 degrees, and when the nucleophile adds it acquires a fourth…
Correct answer: sp2 to sp3- A. a primary alcohol
- B. a secondary alcohol
- C. a tertiary alcohol
- D. a carboxylic acid
Explanation: The alkyl group of the Grignard reagent adds to the carbonyl carbon, which then carries that new group, the original methyl group, a…
Correct answer: a secondary alcohol- A. oximes
- B. esters
- C. alcohols
- D. amines
Explanation: The nitrogen of hydroxylamine attacks the carbonyl carbon and water is then eliminated, so the product contains a carbon to nitrogen…
Correct answer: oximes- A. Formaldehyde
- B. Acetaldehyde
- C. Propanal
- D. Propanone
Explanation: Reducing an aldehyde adds hydrogen across the carbonyl group and gives a primary alcohol with the same number of carbon atoms, so the one…
Correct answer: Formaldehyde- A. Electrophilic addition
- B. Nucleophilic substitution
- C. Nucleophilic addition
- D. Nucleophilic elimination
Explanation: The carbonyl group is polar, with a partially positive carbon atom that is attacked by nucleophiles, followed by addition across the C=O…
Correct answer: Nucleophilic addition- A. Electrophilic addition
- B. Electrophilic substitution
- C. Nucleophilic addition
- D. Necleophilic substitution
Explanation: The cyanide ion from HCN attacks the electrophilic carbonyl carbon of the aldehyde, followed by protonation to give a cyanohydrin, so the…
Correct answer: Nucleophilic addition- A. the presence of halogen atom
- B. the presence of magnesium atom
- C. the polarity of C-Mg bond
- D. all
Explanation: A Grignard reagent is reactive because the C-Mg bond is strongly polar, giving the carbon atom partial negative character and making it a…
Correct answer: the polarity of C-Mg bond- A. increases the nucleophilic character of reagent
- B. increases electrophilic character of carbonyl compound
- C. acidic character of reagent
- D. both a and b
Explanation: A base removes a proton from a nucleophilic reagent such as water, alcohol or a carbon compound, increasing the concentration and…
Correct answer: increases the nucleophilic character of reagent- A. Tartaric acid
- B. Propanoic acid
- C. Lactic acid
- D. Valeric acid
Explanation: Acetaldehyde cyanohydrin is CH3CH(OH)CN. Acid hydrolysis changes the nitrile group, -CN, into a carboxylic acid group, -COOH, giving…
Correct answer: Lactic acid- A. Grignard reagent
- B. Tollens reagent
- C. Fehlings reagent
- D. Benedicts reagent
Explanation: Grignard reagents add to the electrophilic carbonyl carbon of both aldehydes and ketones, producing alcohols after hydrolysis.
Correct answer: Grignard reagent- A. electronphilic addition
- B. electrophilic substitution
- C. nucleophilic addition
- D. nucleophilic substitution
Explanation: In acetone, the carbonyl carbon is electron-deficient, while cyanide ion from HCN acts as the nucleophile and attacks it, followed by…
Correct answer: nucleophilic addition- A. Acid
- B. Base
- C. Both A and B
- D. None
Explanation: Nucleophilic addition can be acid-catalysed by protonating the carbonyl oxygen, which makes the carbonyl carbon more electrophilic, or…
Correct answer: Both A and B- A. Addition - elimination
- B. Electrophilic addition
- C. Free radical addition
- D. Nucleophilic addition
Explanation: The given reaction involves the addition of a nucleophile (NH3) to a carbonyl group of an aldehyde (CH3CHO) to form an imine.
Correct answer: Nucleophilic addition- A. Benzaldehyde
- B. Acetaldehyde
- C. Formaldehyde
- D. Propanaldehyde
Explanation: Formaldehyde is the simplest aldehyde and is highly reactive towards nucleophiles.
Correct answer: Formaldehyde- A. HCHO < CH₃CHO < CH₃COCH₃ < CH₃COCH₃
- B. CH₃CH₂CHO < CH₃COCH₃ < CH₃CHO < HCHO
- C. HCHO < CH₃COCH₃ < CH₃CH₂CHO < CH₃CHO
- D. CH₃COCH₃ < CH₃CH₂CHO < CH₃CHO < HCHO
Explanation: Methyl group is electron donating group hence decreases reactivity
Correct answer: CH₃COCH₃ < CH₃CH₂CHO < CH₃CHO < HCHO- A. Carbon
- B. Magnesium
- C. Halogen
- D. None of the above
Explanation: The explanation for this question will be added soon.
Correct answer: Magnesium- A. Beta hydroxy carboxylic acids
- B. Alpha hydroxy carboxylic acids
- C. Carboxylic acids
- D. Unsaturated acids
Explanation: The hydrolysis of cyanohydrin gives alpha hydroxy, carboxylic acids. In the above reaction, the cyano group is hydrolyzed to a carboxylic…
Correct answer: Alpha hydroxy carboxylic acidsNucleophilic Addition Reactions MCQs: common questions
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