Free Aldehydes and Ketones MCQs with Answers
679 Aldehydes and Ketones MCQs from Chemistry, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Aldehydes and ketones contain the polar carbonyl group, but aldehydes are generally more readily oxidised and more reactive than ketones. Coverage includes preparation by oxidation or reduction routes, nucleophilic addition of reagents such as hydrogen cyanide and bisulfite, and tests that distinguish aldehydes from ketones.
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679 questions · page 14 of 34
- A. Silver mirror test
- B. Fehling's solution
- C. 2, 4 DNPH test
- D. Benedict's solution test
Explanation: Only aldehydes can react with mild reagents such as Fehling's solution and Benedict's solution and also show positive results with the…
Correct answer: 2, 4 DNPH test262. CH3COOH + PCl5 → ?
- A. POCl2, CH3COCl2 and HCl
- B. POCl3 + CH3COCl2 + H2
- C. CH3COCl, POCl2 and HCl
- D. POCl3, CH3COCl and HCl
Explanation: In the given reaction, the acetic acid reacts with PCl5 to form acetyl chloride as a major product, with the production of POCl3 and HCl.
Correct answer: POCl3, CH3COCl and HCl- A. Alkyl halide
- B. Carboxylic acid
- C. Aldehyde
- D. Ester
Explanation: The following is the chemical equation of the reaction. ROH + HCl → RCl + H2O In this reaction, the hydroxyl group (-OH) of the alcohol…
Correct answer: Alkyl halide- A. Alkaline solution
- B. Fehling's solution
- C. A solution containing K2Cr2O7
- D. A solution containing acid only
Explanation: To distinguish between an aldehyde and a ketone, we can use Fehling solution.
Correct answer: Fehling's solution- A. Methanol
- B. Methyl ketone
- C. 3-Hexanol
- D. Propionaldehyde
Explanation: When a methyl ketone is halogenated in a basic solution, the halogen replaces all three α-hydrogen atoms.
Correct answer: Methyl ketone- A. HCHO
- B. CH3 CHO
- C. (CH3)2CO
- D. Have equal reactivity
Explanation: Aldehydes are usually more reactive toward nucleophilic substitutions than ketones because of both steric and electronic effects.
Correct answer: HCHO- A. Propanal
- B. Propanoic acid
- C. Ethanoic acid
- D. Both B and C
Explanation: The reaction can be represented as follows:CH3CH2CH2COCH3 + O2 → CH3COOH + CH3CH2CH2COOHThus the products will be ethanoic acid and…
Correct answer: Both B and C- A. Nucleophilic addition reaction
- B. Unimolecular nucleophilic substitution reaction
- C. Electrophilic substitution reaction
- D. Bimolecular nucleophilic substitution reaction
- E. Nucleophilic elimination reaction
Explanation: A cyanohydrin reaction is an organic chemical reaction by an aldehyde or ketone with a cyanide anion or a nitrile to form a cyanohydrin.
Correct answer: Nucleophilic addition reaction- A. Iodoform test
- B. Schiff's test
- C. Benedict's reagent test
- D. Tollen's test
- E. Cannizzaro test
Explanation: When methyl ketone is heated with iodine in the presence of sodium hydroxide, yellow precipitate of iodoform is obtained.
Correct answer: Iodoform test270. AcetaIs are:
- A. Diethers
- B. Aldehydes
- C. Carboxylic acid
- D. Ketones
Explanation: An acetal is an organic molecule where two separate oxygen atoms are single-bonded to a central carbon atom.
Correct answer: Diethers- A. 3-hydroxy-2-methyl pentanone
- B. 4-hydroxy-4 methyl-2-pentanone
- C. 3-hydroxy butanone
- D. 3-hydroxyl pentanal
Explanation: This is an aldol condensation reaction. It is a reaction in which two molecules of the same or different carbonyl compounds containing…
Correct answer: 4-hydroxy-4 methyl-2-pentanone- A. Amines
- B. Carbonyl compounds
- C. Carboxylic acid
- D. Alkyl halides
Explanation: Iodoform test is used to check the presence of carbonyl compounds with the structure R-CO-CH3 or alcohols with the structure R-CH(OH)-CH3…
Correct answer: Carbonyl compounds- A. More Steric hindrance offered by Its methyl groups
- B. Electron withdrawing nature of its methyl groups
- C. Its Carbonyl carbon is sp2 hybridized
- D. Oxygen of carbonyl group Is more electronegative than carbon atom
Explanation: Aldehydes are typically more reactive than ketones due to the following factors.Aldehydes are less hindered than ketones (a hydrogen atom…
Correct answer: More Steric hindrance offered by Its methyl groups- A. Mango
- B. Raspberry
- C. Apricot
- D. Orange
Explanation: c) Apricot: Amyl butyrate is often used to impart an apricot-like aroma and flavor.
Correct answer: Apricot- A. Fehling's reagent
- B. Grignard's reagent
- C. Schiff's reagent
- D. Tollen's reagent
Explanation: The carbanion nucleophile gives the Grignard Reagent its high reactivity towards Aldehydes and Ketones.
Correct answer: Grignard's reagent- A. Oxygen atom through single bond
- B. Oxygen atom through peptide bond
- C. Oxygen atom through pi-bond
- D. Oxygen atom through a double bond
Explanation: In carbonyl compounds C-atom is attached with O-atom though double bond
Correct answer: Oxygen atom through a double bond- A. Benzaldehyde
- B. Crotonaldehyde
- C. Ethanal
- D. All of these
Explanation: All compounds have -CHO group. Therfore, all the compounds are aldehydes.
Correct answer: All of these- A. Nucleophilic substitution
- B. Electrophilic addition
- C. Nucleophilic addition
- D. Electrophilic substitution
Explanation: The formation of cyanohydrin is achieved by addition of HCN to carbonyl compounds.
Correct answer: Nucleophilic addition279. Which of the following carbonyl compounds does not shows rapid reaction with sodium nitroprusside
- A. Formaldehyde
- B. Acetaldehyde
- C. Benzaldehyde
- D. Acetone
Explanation: Ketones produce a wine red or orange red colour on adding alkaline sodium nitroprusside solution dropwise. Aldehydes do not give this test.
Correct answer: Formaldehyde- A. Formaldehyde
- B. Acetaldehyde
- C. Dimethyl ketone
- D. Propionaldehyde
Explanation: Formaldehyde does not give aldol condensation reactions. This is because formaldehyde is not a beta-hydroxy aldehyde, which is a…
Correct answer: Formaldehyde