Here below some basic MCQ’s about “Aldehydes, Ketones and Carboxylic Acids Preperation and Properties” with answer which is explained in details for exam practice. Let’s check one by one.
1. Which of the following compounds can be prepared by the oxidation of primary alcohols?
a) Ketones
b) Aldehydes
c) Carboxylic acids
d) Esters
Answer: b) Aldehydes
Explanation: Primary alcohols are oxidized to aldehydes under controlled conditions (with reagents like PCC, CrO₃, etc.). Further oxidation of aldehydes leads to carboxylic acids.
2. The reagent used for the oxidation of secondary alcohols to ketones is:
a) Tollen’s reagent
b) PCC (Pyridinium chlorochromate)
c) Fehling’s solution
d) Grignard reagent
Answer: b) PCC (Pyridinium chlorochromate)
Explanation: Secondary alcohols are oxidized to ketones using oxidizing agents such as PCC, which selectively oxidizes secondary alcohols without over-oxidizing.
3. Which of the following methods is used to prepare aldehydes from alkenes?
a) Ozonolysis
b) Hydroboration-oxidation
c) Friedel-Crafts acylation
d) Wurtz reaction
Answer: a) Ozonolysis
Explanation: Ozonolysis of alkenes involves cleavage of the double bond, producing aldehydes or ketones depending on the structure of the alkene.
4. Which of the following reagents is used to reduce carboxylic acids to primary alcohols?
a) LiAlH₄ (Lithium aluminium hydride)
b) KMnO₄ (Potassium permanganate)
c) H₂/Pd
d) PCC (Pyridinium chlorochromate)
Answer: a) LiAlH₄
Explanation: Lithium aluminium hydride (LiAlH₄) is a strong reducing agent that reduces carboxylic acids to primary alcohols. It does not stop at the aldehyde stage.
5. Which of the following is the correct order of reactivity towards nucleophilic addition reactions?
a) Ketones > Aldehydes > Carboxylic acids
b) Carboxylic acids > Ketones > Aldehydes
c) Aldehydes > Ketones > Carboxylic acids
d) Ketones > Carboxylic acids > Aldehydes
Answer: c) Aldehydes > Ketones > Carboxylic acids
Explanation: Aldehydes are more reactive than ketones because of less steric hindrance and greater electrophilicity. Carboxylic acids are the least reactive due to resonance stabilization and the presence of the electron-withdrawing -OH group.
6. Which of the following reagents will convert an aldehyde into a carboxylic acid?
a) PCC
b) Fehling’s solution
c) KMnO₄
d) NaBH₄
Answer: c) KMnO₄
Explanation: Potassium permanganate (KMnO₄) is a strong oxidizing agent that oxidizes aldehydes to carboxylic acids.
7. Which of the following reagents is used for the reduction of aldehydes to primary alcohols?
a) LiAlH₄
b) NaBH₄
c) H₂/Pt
d) All of the above
Answer: d) All of the above
Explanation: LiAlH₄, NaBH₄, and catalytic hydrogenation (H₂/Pt) all reduce aldehydes to primary alcohols. NaBH₄ is milder compared to LiAlH₄.
8. Which of the following compounds does not give a positive Tollen’s test?
a) Formaldehyde
b) Benzaldehyde
c) Acetone
d) Acetaldehyde
Answer: c) Acetone
Explanation: Tollen’s reagent is used to test for aldehydes. Since acetone is a ketone, it does not give a positive Tollen’s test.
9. The IUPAC name of CH₃-CO-CH₃ is:
a) Propanal
b) Propanone
c) Acetone
d) Acetic acid
Answer: b) Propanone
Explanation: The IUPAC name of the simplest ketone (CH₃-CO-CH₃) is propanone. It is commonly known as acetone.
10. Which of the following methods can be used to prepare ketones?
a) Oxidation of secondary alcohols
b) Ozonolysis of alkenes
c) Friedel-Crafts acylation
d) All of the above
Answer: d) All of the above
Explanation: Ketones can be prepared by the oxidation of secondary alcohols, the ozonolysis of alkenes, and the Friedel-Crafts acylation of aromatic compounds with acid chlorides.
11. Which of the following compounds is the least reactive towards nucleophilic addition reactions?
a) Formaldehyde
b) Acetaldehyde
c) Acetone
d) Benzaldehyde
Answer: d) Benzaldehyde
Explanation: Benzaldehyde is less reactive than aliphatic aldehydes and ketones due to the electron-withdrawing nature of the benzene ring, which decreases the electrophilicity of the carbonyl carbon.
12. Which of the following carboxylic acids is the strongest acid?
a) Formic acid
b) Acetic acid
c) Benzoic acid
d) Chloroacetic acid
Answer: d) Chloroacetic acid
Explanation: Chloroacetic acid is the strongest acid due to the electron-withdrawing effect of the chlorine atom, which stabilizes the negative charge on the conjugate base.
13. Which of the following compounds will not undergo the Cannizzaro reaction?
a) Formaldehyde
b) Acetaldehyde
c) Benzaldehyde
d) Trimethylacetaldehyde
Answer: b) Acetaldehyde
Explanation: The Cannizzaro reaction occurs with aldehydes that lack alpha-hydrogens. Acetaldehyde has an alpha-hydrogen, so it undergoes aldol condensation rather than the Cannizzaro reaction.
14. Which of the following is the correct order of acidity?
a) Formic acid > Acetic acid > Benzoic acid
b) Benzoic acid > Formic acid > Acetic acid
c) Formic acid > Benzoic acid > Acetic acid
d) Acetic acid > Formic acid > Benzoic acid
Answer: c) Formic acid > Benzoic acid > Acetic acid
Explanation: Formic acid is more acidic than both acetic acid and benzoic acid due to the absence of electron-donating alkyl or phenyl groups. Benzoic acid is more acidic than acetic acid due to the electron-withdrawing effect of the phenyl group.
15. Aldol condensation involves the reaction between:
a) Two ketones
b) Two aldehydes
c) An aldehyde and a ketone
d) All of the above
Answer: d) All of the above
Explanation: Aldol condensation involves compounds that have alpha-hydrogens. Both aldehydes and ketones can undergo aldol condensation, either with themselves or with each other.
16. Which of the following compounds does not undergo aldol condensation?
a) Formaldehyde
b) Acetaldehyde
c) Acetone
d) Benzaldehyde
Answer: a) Formaldehyde
Explanation: Formaldehyde lacks alpha-hydrogens, which are necessary for aldol condensation to occur.
17. Which reagent is used for the decarboxylation of carboxylic acids?
a) NaOH and CaO
b) LiAlH₄
c) KMnO₄
d) PCC
Answer: a) NaOH and CaO
Explanation: Decarboxylation of carboxylic acids is typically carried out using soda lime (a mixture of NaOH and CaO), which removes the carboxyl group as carbon dioxide.
18. Which of the following is the most reactive toward nucleophilic acyl substitution?
a) Acetic acid
b) Acetyl chloride
c) Acetic anhydride
d) Methyl acetate
Answer: b) Acetyl chloride
Explanation: Acetyl chloride is the most reactive towards nucleophilic acyl substitution due to the presence of the highly electronegative chlorine atom, which makes the carbonyl carbon more electrophilic.
19. Which of the following carboxylic acids undergoes decarboxylation most easily?
a) Oxalic acid
b) Malonic acid
c) Succinic acid
d) Glutaric acid
Answer: b) Malonic acid
Explanation: Malonic acid undergoes decarboxylation easily because the product, acetic acid, is stabilized by resonance.
20. Which of the following reactions is used to prepare carboxylic acids from alkyl halides?
a) Grignard reaction
b) Kolbe’s reaction
c) Wurtz reaction
d) Finkelstein reaction
Answer: b) Kolbe’s reaction
Explanation: In Kolbe’s reaction, an alkyl halide reacts with carbon dioxide in the presence of a base to form a carboxylate ion, which is then protonated to give a carboxylic acid.
21. Which of the following methods is used to prepare carboxylic acids from nitriles?
a) Hydrolysis
b) Hydrogenation
c) Oxidation
d) Dehydration
Answer: a) Hydrolysis
Explanation: Nitriles are hydrolyzed in acidic or basic conditions to form carboxylic acids. The nitrile group (–CN) is converted into a carboxyl group (–COOH).
22. The reduction of a carboxylic acid to an aldehyde can be accomplished using which reagent?
a) LiAlH₄
b) NaBH₄
c) DIBAL-H (Diisobutylaluminium hydride)
d) H₂/Pd
Answer: c) DIBAL-H (Diisobutylaluminium hydride)
Explanation: DIBAL-H reduces carboxylic acids selectively to aldehydes under controlled conditions, unlike LiAlH₄, which reduces them directly to primary alcohols.
23. Which of the following gives a positive iodoform test?
a) Formaldehyde
b) Acetone
c) Benzaldehyde
d) Propionaldehyde
Answer: b) Acetone
Explanation: The iodoform test is positive for compounds with a methyl ketone group (-COCH₃). Acetone contains this group, so it gives a positive test.
24. Which of the following reactions is used to prepare benzaldehyde from toluene?
a) Friedel-Crafts acylation
b) Clemmensen reduction
c) Etard reaction
d) Cannizzaro reaction
Answer: c) Etard reaction
Explanation: In the Etard reaction, toluene is oxidized to benzaldehyde using chromyl chloride (CrO₂Cl₂).
25. Which reagent will selectively oxidize an aldehyde to a carboxylic acid, leaving a secondary alcohol unchanged?
a) Tollen’s reagent
b) LiAlH₄
c) NaBH₄
d) PCC
Answer: a) Tollen’s reagent
Explanation: Tollen’s reagent oxidizes aldehydes to carboxylic acids but does not affect secondary alcohols, making it selective for aldehydes.
26. Which of the following is the most acidic?
a) Formic acid
b) Acetic acid
c) Trichloroacetic acid
d) Benzoic acid
Answer: c) Trichloroacetic acid
Explanation: Trichloroacetic acid is the most acidic due to the strong electron-withdrawing effect of the three chlorine atoms, which stabilize the negative charge on the conjugate base.
27. Which of the following compounds will undergo nucleophilic addition reactions most readily?
a) Acetone
b) Acetaldehyde
c) Formaldehyde
d) Benzaldehyde
Answer: c) Formaldehyde
Explanation: Formaldehyde is the most reactive towards nucleophilic addition due to the absence of any alkyl or aryl group, which reduces steric hindrance and increases the electrophilicity of the carbonyl carbon.
28. Which of the following carboxylic acids undergoes the fastest esterification reaction with methanol?
a) Formic acid
b) Acetic acid
c) Benzoic acid
d) Propanoic acid
Answer: a) Formic acid
Explanation: Formic acid undergoes the fastest esterification because it has no alkyl or aryl group to provide steric hindrance, and it is more reactive than acetic or benzoic acid.
29. In the reaction of an aldehyde with a Grignard reagent, the product formed is:
a) Primary alcohol
b) Secondary alcohol
c) Tertiary alcohol
d) Ketone
Answer: b) Secondary alcohol
Explanation: The reaction of an aldehyde with a Grignard reagent produces a secondary alcohol after hydrolysis.
30. Which of the following will not react with Fehling’s solution?
a) Glucose
b) Benzaldehyde
c) Formaldehyde
d) Acetaldehyde
Answer: b) Benzaldehyde
Explanation: Benzaldehyde does not react with Fehling’s solution because it is an aromatic aldehyde. Fehling’s solution is typically used to test for aliphatic aldehydes, which are easily oxidized.
31. Which of the following compounds is formed when acetic acid reacts with phosphorus pentachloride (PCl₅)?
a) Acetyl chloride
b) Acetaldehyde
c) Acetone
d) Ethanol
Answer: a) Acetyl chloride
Explanation: Acetic acid reacts with phosphorus pentachloride (PCl₅) to form acetyl chloride and phosphorus oxychloride (POCl₃).
32. The reaction of an aldehyde or ketone with hydroxylamine (NH₂OH) forms:
a) An oxime
b) A hydrazone
c) A cyanohydrin
d) A semicarbazone
Answer: a) An oxime
Explanation: Aldehydes and ketones react with hydroxylamine (NH₂OH) to form oximes.
33. Which of the following is not a reducing agent for the reduction of aldehydes and ketones?
a) NaBH₄
b) H₂/Ni
c) LiAlH₄
d) PCC
Answer: d) PCC
Explanation: PCC (Pyridinium chlorochromate) is an oxidizing agent, not a reducing agent. It is used to oxidize alcohols to aldehydes or ketones.
34. In the Clemmensen reduction, the reagent used is:
a) Zn/Hg in HCl
b) NaBH₄
c) LiAlH₄
d) H₂/Pd
Answer: a) Zn/Hg in HCl
Explanation: Clemmensen reduction involves the reduction of aldehydes or ketones to hydrocarbons using zinc amalgam (Zn/Hg) in hydrochloric acid.
35. Which of the following is the correct order of boiling points for carboxylic acids, aldehydes, and ketones?
a) Carboxylic acids > Aldehydes > Ketones
b) Carboxylic acids > Ketones > Aldehydes
c) Aldehydes > Ketones > Carboxylic acids
d) Ketones > Carboxylic acids > Aldehydes
Answer: b) Carboxylic acids > Ketones > Aldehydes
Explanation: Carboxylic acids have the highest boiling points due to hydrogen bonding. Ketones have higher boiling points than aldehydes because of their greater molecular mass and dipole interactions.
36. Which of the following compounds does not undergo the Cannizzaro reaction?
a) Formaldehyde
b) Benzaldehyde
c) Acetone
d) Trimethylacetaldehyde
Answer: c) Acetone
Explanation: Acetone is a ketone and does not undergo the Cannizzaro reaction, which is specific to aldehydes without alpha-hydrogens.
37. When propanoic acid is treated with phosphorus pentachloride, the product is:
a) Propionyl chloride
b) Propanal
c) Propanone
d) Propanol
Answer: a) Propionyl chloride
Explanation: Propanoic acid reacts with phosphorus pentachloride (PCl₅) to form propionyl chloride and phosphorus oxychloride.
38. Which of the following aldehydes is the least reactive towards nucleophilic addition?
a) Formaldehyde
b) Acetaldehyde
c) Benzaldehyde
d) Propanal
Answer: c) Benzaldehyde
Explanation: Benzaldehyde is less reactive due to the electron-withdrawing effect of the benzene ring, which stabilizes the carbonyl carbon and reduces its electrophilicity.
39. The reaction of an aldehyde with hydrogen cyanide (HCN) forms:
a) An alcohol
b) A cyanohydrin
c) An ester
d) A nitrile
Answer: b) A cyanohydrin
Explanation: Aldehydes react with hydrogen cyanide (HCN) to form cyanohydrins, which contain both a hydroxyl group and a nitrile group.
40. Which of the following compounds undergoes the haloform reaction?
a) Acetone
b) Benzaldehyde
c) Methanal
d) Propanal
Answer: a) Acetone
Explanation: Acetone has a methyl ketone group, which is required for the haloform reaction to occur. This reaction produces iodoform (CHI₃) when iodine is used.
41. Which of the following is the main product when acetone undergoes aldol condensation?
a) Acetic acid
b) Acetaldehyde
c) Mesityl oxide
d) Benzaldehyde
Answer: c) Mesityl oxide
Explanation: When acetone undergoes aldol condensation, it first forms a β-hydroxy ketone, which upon dehydration gives mesityl oxide (CH₃COCH=CH₂COCH₃).
42. Which of the following will not give a positive Schiff’s test?
a) Acetaldehyde
b) Formaldehyde
c) Benzaldehyde
d) Acetone
Answer: d) Acetone
Explanation: Schiff’s test is used to detect aldehydes. Ketones, such as acetone, do not react positively with Schiff’s reagent.
43. Which of the following reactions produces a carboxylic acid from an alkene?
a) Ozonolysis followed by oxidation
b) Hydroboration-oxidation
c) Wurtz reaction
d) Friedel-Crafts alkylation
Answer: a) Ozonolysis followed by oxidation
Explanation: Ozonolysis of an alkene cleaves the double bond to form aldehydes, which can be further oxidized to carboxylic acids.
44. Which of the following compounds does not undergo oxidation with Tollen’s reagent?
a) Formaldehyde
b) Acetaldehyde
c) Benzaldehyde
d) Acetone
Answer: d) Acetone
Explanation: Tollen’s reagent is specific for aldehydes. Acetone, being a ketone, does not undergo oxidation with Tollen’s reagent.
45. Which of the following carboxylic acids is the least acidic?
a) Formic acid
b) Acetic acid
c) Benzoic acid
d) Phenylacetic acid
Answer: d) Phenylacetic acid
Explanation: Phenylacetic acid is less acidic than benzoic acid because the phenyl group in phenylacetic acid is separated from the carboxyl group by a methylene (-CH₂-) group, reducing the electron-withdrawing effect.
46. Which of the following compounds gives a yellow precipitate with iodine and NaOH (Iodoform test)?
a) Ethanol
b) Propanol
c) Methanol
d) Isopropanol
Answer: d) Isopropanol
Explanation: Isopropanol contains the CH₃CHOH– group, which gives a positive iodoform test, resulting in the formation of yellow iodoform (CHI₃).
47. Which of the following acids will undergo decarboxylation most readily?
a) Acetic acid
b) Malonic acid
c) Oxalic acid
d) Succinic acid
Answer: b) Malonic acid
Explanation: Malonic acid undergoes decarboxylation easily because the reaction results in the formation of a stable carboxylate ion, followed by protonation to give acetic acid.
48. Which of the following aldehydes will undergo the Cannizzaro reaction?
a) Formaldehyde
b) Acetaldehyde
c) Benzaldehyde
d) Propanal
Answer: c) Benzaldehyde
Explanation: The Cannizzaro reaction is undergone by aldehydes that do not have alpha-hydrogens. Benzaldehyde, lacking alpha-hydrogens, undergoes the Cannizzaro reaction.
49. The product obtained from the reaction of formaldehyde with Grignard reagent followed by hydrolysis is:
a) Primary alcohol
b) Secondary alcohol
c) Tertiary alcohol
d) Ketone
Answer: a) Primary alcohol
Explanation: Formaldehyde reacts with a Grignard reagent to give a primary alcohol after hydrolysis.
50. The product of oxidation of an aldehyde with Fehling’s solution is:
a) Alcohol
b) Ketone
c) Carboxylic acid
d) Ester
Answer: c) Carboxylic acid
Explanation: Fehling’s solution oxidizes aldehydes to carboxylic acids by converting the aldehyde group (-CHO) to a carboxyl group (-COOH).
51. Which of the following statements is correct about the structure of formaldehyde?
a) It contains a double bond between carbon and oxygen
b) It contains a triple bond between carbon and oxygen
c) It contains a hydroxyl group (-OH)
d) It contains an ester group (-COOR)
Answer: a) It contains a double bond between carbon and oxygen
Explanation: Formaldehyde (HCHO) contains a carbonyl group (C=O), which consists of a double bond between carbon and oxygen.
52. Which of the following compounds will undergo nucleophilic substitution?
a) Acetaldehyde
b) Acetone
c) Acetyl chloride
d) Benzaldehyde
Answer: c) Acetyl chloride
Explanation: Acetyl chloride contains a good leaving group (Cl⁻), making it susceptible to nucleophilic substitution reactions.
53. Which of the following statements is correct about the Cannizzaro reaction?
a) It occurs in aldehydes without alpha-hydrogens
b) It occurs in ketones without alpha-hydrogens
c) It involves nucleophilic addition to aldehydes
d) It involves oxidation of alcohols
Answer: a) It occurs in aldehydes without alpha-hydrogens
Explanation: The Cannizzaro reaction occurs in aldehydes that lack alpha-hydrogens, leading to the simultaneous oxidation and reduction of two aldehyde molecules.
54. Which of the following reactions will convert an alkene into an aldehyde?
a) Hydroboration-oxidation
b) Ozonolysis
c) Friedel-Crafts acylation
d) Grignard reaction
Answer: b) Ozonolysis
Explanation: Ozonolysis of alkenes cleaves the carbon-carbon double bond, forming aldehydes or ketones depending on the structure of the alkene.
55. The reaction of a ketone with hydrazine (NH₂NH₂) followed by heating in basic conditions produces:
a) Alcohol
b) Alkane
c) Amine
d) Aldehyde
Answer: b) Alkane
Explanation: The Wolff-Kishner reduction involves the conversion of a ketone into an alkane by treatment with hydrazine followed by heating under basic conditions.
56. Which of the following compounds will give a positive iodoform test?
a) Propanone
b) Acetaldehyde
c) Benzaldehyde
d) Propanal
Answer: a) Propanone
Explanation: Propanone (CH₃COCH₃) gives a positive iodoform test because it contains the methyl ketone group (-COCH₃).
57. Which of the following statements is correct regarding ketones?
a) Ketones cannot be oxidized under normal conditions
b) Ketones can be easily oxidized to carboxylic acids
c) Ketones can be reduced to primary alcohols
d) Ketones undergo oxidation with Tollen’s reagent
Answer: a) Ketones cannot be oxidized under normal conditions
Explanation: Ketones are relatively resistant to oxidation under normal conditions. Strong oxidizing agents may break the carbon-carbon bond to form carboxylic acids, but this is not common under mild conditions.
58. Which of the following will give a positive Tollen’s test?
a) Acetone
b) Acetaldehyde
c) Benzene
d) Propanone
Answer: b) Acetaldehyde
Explanation: Tollen’s reagent reacts with aldehydes like acetaldehyde, oxidizing them to carboxylic acids and producing a silver mirror.
59. The reaction between benzaldehyde and acetone in the presence of dilute NaOH is an example of:
a) Cannizzaro reaction
b) Aldol condensation
c) Perkin reaction
d) Benzoin condensation
Answer: b) Aldol condensation
Explanation: In the presence of dilute NaOH, acetone and benzaldehyde undergo aldol condensation to form a β-hydroxy ketone, which can further dehydrate to form an α,β-unsaturated ketone.
60. Which of the following is formed when acetone reacts with methylmagnesium bromide followed by hydrolysis?
a) Primary alcohol
b) Secondary alcohol
c) Tertiary alcohol
d) Ketone
Answer: c) Tertiary alcohol
Explanation: The reaction of a ketone like acetone with a Grignard reagent (methylmagnesium bromide) followed by hydrolysis produces a tertiary alcohol.
61. Which of the following compounds is the least reactive towards nucleophilic addition reactions?
a) Formaldehyde
b) Acetaldehyde
c) Acetone
d) Benzaldehyde
Answer: d) Benzaldehyde
Explanation: Benzaldehyde is less reactive towards nucleophilic addition reactions due to the electron-withdrawing resonance effect of the benzene ring, which reduces the electrophilicity of the carbonyl carbon.
62. In the Hell-Volhard-Zelinsky reaction, which of the following reagents is used?
a) PCl₃ and Br₂
b) HCl and Br₂
c) HBr and Cl₂
d) NaOH and Cl₂
Answer: a) PCl₃ and Br₂
Explanation: In the Hell-Volhard-Zelinsky reaction, a carboxylic acid is halogenated at the alpha position using phosphorus trichloride (PCl₃) and bromine (Br₂).
63. Which of the following aldehydes will undergo oxidation most easily?
a) Formaldehyde
b) Acetaldehyde
c) Benzaldehyde
d) Propionaldehyde
Answer: a) Formaldehyde
Explanation: Formaldehyde is the simplest aldehyde and undergoes oxidation most easily to formic acid due to the absence of bulky groups around the carbonyl carbon.
64. Which of the following reactions is used to prepare ketones from acyl chlorides?
a) Friedel-Crafts acylation
b) Wolff-Kishner reduction
c) Clemmensen reduction
d) Wurtz reaction
Answer: a) Friedel-Crafts acylation
Explanation: In Friedel-Crafts acylation, an acyl chloride reacts with an aromatic compound in the presence of AlCl₃ to form a ketone.
65. Which of the following reactions can be used to synthesize acetaldehyde from ethyne?
a) Hydroboration-oxidation
b) Ozonolysis
c) Catalytic hydrogenation
d) Hydration in the presence of Hg²⁺
Answer: d) Hydration in the presence of Hg²⁺
Explanation: The hydration of ethyne (acetylene) in the presence of mercury(II) salts gives acetaldehyde through the formation of an enol, which tautomerizes to the aldehyde.
66. Which of the following will undergo decarboxylation most readily upon heating?
a) Benzoic acid
b) Oxalic acid
c) Malonic acid
d) Acetic acid
Answer: c) Malonic acid
Explanation: Malonic acid undergoes decarboxylation easily due to the presence of two carboxyl groups adjacent to each other, which facilitates the release of CO₂ upon heating.
67. In the reaction of an aldehyde with a cyanide ion, the intermediate product is:
a) Alcohol
b) Nitrile
c) Cyanohydrin
d) Acetal
Answer: c) Cyanohydrin
Explanation: The cyanide ion (CN⁻) adds to the carbonyl group of an aldehyde to form a cyanohydrin, which contains both a hydroxyl (-OH) group and a nitrile (-CN) group.
68. The Cannizzaro reaction involves:
a) Reduction of an aldehyde
b) Oxidation of an alcohol
c) Simultaneous oxidation and reduction of two molecules of an aldehyde
d) Oxidation of a ketone
Answer: c) Simultaneous oxidation and reduction of two molecules of an aldehyde
Explanation: The Cannizzaro reaction involves the disproportionation of two molecules of an aldehyde (without alpha-hydrogens), where one is oxidized to a carboxylic acid and the other is reduced to an alcohol.
69. Which of the following carboxylic acids undergoes Kolbe’s electrolysis?
a) Acetic acid
b) Benzoic acid
c) Formic acid
d) Oxalic acid
Answer: a) Acetic acid
Explanation: In Kolbe’s electrolysis, carboxylate anions, such as those from acetic acid, are electrolyzed to form alkanes. For acetic acid, this results in the formation of ethane.
70. The oxidation of acetaldehyde with potassium dichromate gives:
a) Ethanol
b) Acetone
c) Acetic acid
d) Formaldehyde
Answer: c) Acetic acid
Explanation: Potassium dichromate is a strong oxidizing agent, and it oxidizes acetaldehyde to acetic acid by converting the aldehyde group to a carboxyl group.
71. Which of the following reagents can convert a carboxylic acid into an ester?
a) HCl
b) NaOH
c) H₂SO₄
d) NaBH₄
Answer: c) H₂SO₄
Explanation: Sulfuric acid (H₂SO₄) acts as a catalyst in the esterification reaction, where a carboxylic acid reacts with an alcohol to form an ester and water.
72. Which of the following does not undergo an aldol condensation reaction?
a) Acetaldehyde
b) Benzaldehyde
c) Acetone
d) Propanal
Answer: b) Benzaldehyde
Explanation: Benzaldehyde does not undergo aldol condensation because it lacks alpha-hydrogens, which are required for the enolate formation step of the reaction.
73. Which of the following compounds reacts with a Grignard reagent to form a tertiary alcohol?
a) Formaldehyde
b) Acetone
c) Benzaldehyde
d) Acetaldehyde
Answer: b) Acetone
Explanation: Acetone reacts with a Grignard reagent to form a tertiary alcohol after hydrolysis.
74. The reaction of a carboxylic acid with ammonia forms:
a) Amine
b) Amide
c) Alcohol
d) Aldehyde
Answer: b) Amide
Explanation: The reaction of a carboxylic acid with ammonia (NH₃) results in the formation of an amide (RCONH₂) through a condensation reaction.
75. Which of the following reagents will oxidize a primary alcohol to an aldehyde but not to a carboxylic acid?
a) PCC (Pyridinium chlorochromate)
b) KMnO₄
c) K₂Cr₂O₇
d) Na₂Cr₂O₇
Answer: a) PCC (Pyridinium chlorochromate)
Explanation: PCC is a mild oxidizing agent that oxidizes primary alcohols to aldehydes without further oxidizing them to carboxylic acids.
76. Which of the following carboxylic acids has the highest acidity?
a) Acetic acid
b) Formic acid
c) Propanoic acid
d) Trifluoroacetic acid
Answer: d) Trifluoroacetic acid
Explanation: Trifluoroacetic acid is highly acidic due to the strong electron-withdrawing effect of the fluorine atoms, which stabilize the conjugate base (carboxylate anion).
77. Which of the following reagents will convert an aldehyde into a primary alcohol?
a) NaBH₄
b) H₂SO₄
c) KMnO₄
d) HNO₃
Answer: a) NaBH₄
Explanation: Sodium borohydride (NaBH₄) is a reducing agent that converts aldehydes into primary alcohols by reducing the carbonyl group.
78. Which of the following aldehydes does not undergo nucleophilic addition reactions?
a) Formaldehyde
b) Acetaldehyde
c) Benzaldehyde
d) Methanal
Answer: c) Benzaldehyde
Explanation: Benzaldehyde is less reactive towards nucleophilic addition due to the electron-withdrawing effect of the benzene ring, which stabilizes the carbonyl group.
79. Which of the following statements is correct about ketones?
a) Ketones can undergo oxidation to form primary alcohols
b) Ketones can be reduced to secondary alcohols
c) Ketones can be oxidized to carboxylic acids under mild conditions
d) Ketones undergo nucleophilic substitution reactions
Answer: b) Ketones can be reduced to secondary alcohols
Explanation: Ketones are reduced to secondary alcohols using reducing agents such as NaBH₄ or LiAlH₄.
80. Which of the following reactions is used to prepare benzaldehyde from benzyl chloride?
a) Oxidation with KMnO₄
b) Reduction with NaBH₄
c) Hydrolysis in the presence of dilute HCl
d) Hydrolysis in the presence of NaOH
Answer: d) Hydrolysis in the presence of NaOH
Explanation: Benzaldehyde can be prepared from benzyl chloride through basic hydrolysis, which removes the chlorine atom and forms the aldehyde group.
81. Which of the following compounds will give a positive 2,4-DNP test?
a) Ethanol
b) Acetone
c) Acetic acid
d) Benzene
Answer: b) Acetone
Explanation: The 2,4-DNP (2,4-Dinitrophenylhydrazine) test is used to detect carbonyl groups in aldehydes and ketones. Acetone, being a ketone, gives a positive result.
82. The oxidation of propanal using potassium permanganate yields:
a) Propanol
b) Propanoic acid
c) Propanone
d) Ethanol
Answer: b) Propanoic acid
Explanation: Potassium permanganate (KMnO₄) is a strong oxidizing agent that converts aldehydes like propanal into their corresponding carboxylic acids, in this case, propanoic acid.
83. Which of the following will produce benzaldehyde upon oxidation?
a) Toluene
b) Benzyl alcohol
c) Phenol
d) Benzoic acid
Answer: b) Benzyl alcohol
Explanation: Oxidation of benzyl alcohol leads to the formation of benzaldehyde.
84. The reaction of an aldehyde with two equivalents of an alcohol in the presence of an acid catalyst forms:
a) Hemiacetal
b) Acetal
c) Ketal
d) Alcohol
Answer: b) Acetal
Explanation: When an aldehyde reacts with two equivalents of an alcohol under acidic conditions, it forms an acetal, which has two alkoxy groups attached to the same carbon atom.
85. The product of the reaction of acetone with methylamine (CH₃NH₂) is:
a) Alcohol
b) Imine
c) Nitrile
d) Amide
Answer: b) Imine
Explanation: The reaction of a ketone (acetone) with a primary amine (methylamine) results in the formation of an imine (Schiff base), which contains a C=N bond.
86. Which of the following compounds does not undergo the iodoform test?
a) Ethanol
b) Acetaldehyde
c) Acetone
d) Methanol
Answer: d) Methanol
Explanation: Methanol does not undergo the iodoform test because it lacks the necessary CH₃CO- or CH₃CH(OH)- group, which is required for a positive result.
87. In the decarboxylation of carboxylic acids, which of the following is usually eliminated?
a) Hydrogen
b) Oxygen
c) Carbon dioxide
d) Nitrogen
Answer: c) Carbon dioxide
Explanation: Decarboxylation is the loss of carbon dioxide (CO₂) from a carboxylic acid, leaving behind a hydrocarbon or derivative.
88. The product of the reaction of formaldehyde with an excess of Grignard reagent (CH₃MgBr) followed by hydrolysis is:
a) Primary alcohol
b) Secondary alcohol
c) Tertiary alcohol
d) Carboxylic acid
Answer: a) Primary alcohol
Explanation: The reaction of formaldehyde with a Grignard reagent, followed by hydrolysis, gives a primary alcohol. In this case, methanol is produced.
89. Which of the following compounds will give a positive Fehling’s test?
a) Acetone
b) Benzaldehyde
c) Acetaldehyde
d) Benzene
Answer: c) Acetaldehyde
Explanation: Fehling’s test is used to detect reducing sugars and aldehydes. Acetaldehyde gives a positive test, forming a brick-red precipitate of copper(I) oxide.
90. Which of the following reagents will convert an aldehyde into a carboxylic acid?
a) NaBH₄
b) KMnO₄
c) LiAlH₄
d) H₂/Pt
Answer: b) KMnO₄
Explanation: Potassium permanganate (KMnO₄) is a strong oxidizing agent that converts aldehydes into carboxylic acids.
91. Which of the following reagents is used in the Wolff-Kishner reduction?
a) H₂SO₄
b) Hydrazine
c) Zinc amalgam
d) PCC
Answer: b) Hydrazine
Explanation: The Wolff-Kishner reduction involves the conversion of a ketone or aldehyde into an alkane using hydrazine (NH₂NH₂) in basic conditions.
92. The reaction of benzaldehyde with sodium hydroxide (NaOH) produces:
a) Benzoic acid
b) Benzyl alcohol
c) Benzoin
d) Benzaldehyde and benzoic acid
Answer: d) Benzaldehyde and benzoic acid
Explanation: In the Cannizzaro reaction, two molecules of benzaldehyde react with sodium hydroxide. One is oxidized to benzoic acid, and the other is reduced to benzyl alcohol.
93. Which of the following reagents will convert acetone into a secondary alcohol?
a) NaBH₄
b) H₂O₂
c) KMnO₄
d) Br₂
Answer: a) NaBH₄
Explanation: Sodium borohydride (NaBH₄) is a reducing agent that converts ketones like acetone into secondary alcohols.
94. Which of the following acids is the most acidic?
a) Formic acid
b) Acetic acid
c) Propanoic acid
d) Butanoic acid
Answer: a) Formic acid
Explanation: Formic acid (HCOOH) is more acidic than acetic acid and other higher carboxylic acids because it lacks alkyl groups that would reduce the acidity by donating electron density.
95. Which of the following is not an intermediate in the aldol condensation reaction?
a) Enolate ion
b) Aldehyde
c) Ketone
d) Alkane
Answer: d) Alkane
Explanation: In an aldol condensation, an enolate ion reacts with an aldehyde or ketone, but alkanes are not involved in the reaction mechanism.
96. The Perkin reaction is used to synthesize:
a) Esters
b) Aldehydes
c) Alpha, beta-unsaturated acids
d) Amines
Answer: c) Alpha, beta-unsaturated acids
Explanation: The Perkin reaction is a method for synthesizing alpha, beta-unsaturated acids by condensing an aromatic aldehyde with an acid anhydride.
97. Which of the following reagents is used to selectively reduce an aldehyde to a primary alcohol?
a) H₂SO₄
b) NaBH₄
c) CrO₃
d) NaOH
Answer: b) NaBH₄
Explanation: Sodium borohydride (NaBH₄) is a selective reducing agent that converts aldehydes into primary alcohols without affecting other functional groups.
98. Which of the following statements is correct about ketones?
a) Ketones can be reduced to primary alcohols
b) Ketones can be reduced to secondary alcohols
c) Ketones are oxidized to aldehydes
d) Ketones undergo reduction with KMnO₄
Answer: b) Ketones can be reduced to secondary alcohols
Explanation: Ketones are reduced to secondary alcohols using reducing agents like NaBH₄ or LiAlH₄.
99. Which of the following compounds will react with sodium bicarbonate (NaHCO₃)?
a) Ethanol
b) Acetic acid
c) Acetone
d) Ethyl acetate
Answer: b) Acetic acid
Explanation: Acetic acid reacts with sodium bicarbonate to form carbon dioxide (CO₂), water, and sodium acetate. Only acids react with NaHCO₃.
100. Which of the following aldehydes undergoes the Cannizzaro reaction?
a) Acetaldehyde
b) Benzaldehyde
c) Propanal
d) Butanal
Answer: b) Benzaldehyde
Explanation: Benzaldehyde undergoes the Cannizzaro reaction because it lacks alpha-hydrogens, making it suitable for this disproportionation reaction.
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