Aldehydes, Ketones & Carboxylic Acids

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| By Tanmay Shankar
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Tanmay Shankar
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  • 1/15 Questions

    Among the following acids which has the lowest pKa value?

    • CH3COOH
    • HCOOH
    • (CH3)2CHCOOH
    • CH3CH2COOH
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Aldehydes, Ketones & Carboxylic Acids - Quiz
About This Quiz

This online test focuses on reactions and properties of aldehydes, ketones, and carboxylic acids. It assesses understanding of chemical reactions, identification of compounds, and analysis of molecular structures, crucial for students in advanced chemistry courses.

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  • 2. 

    During reduction of aldehydes with hydrazine and potassium hydroxide, the first is formation of:

    • R-C≡N

    • R-CO-NH2

    • R-CH=NH

    • R-CH=N-NH2

    Correct Answer
    A. R-CH=N-NH2
    Explanation
    The reduction of aldehydes with hydrazine and potassium hydroxide leads to the formation of R-CH=N-NH2. This is because hydrazine (N2H4) acts as a reducing agent and reacts with the aldehyde functional group (R-CHO) to form an imine (R-CH=NH). The imine then undergoes further reduction with hydrazine to form the desired product, R-CH=N-NH2, which is a hydrazone.

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  • 3. 

    Which of the following reagents may be used to distinguish between phenol and benzoic acid?

    • Tollens’ reagent

    • Molisch reagent

    • Neutral FeCl3

    • Aqueous NaOH

    Correct Answer
    A. Neutral FeCl3
    Explanation
    Neutral FeCl3 can be used to distinguish between phenol and benzoic acid because it reacts differently with each compound. When phenol is added to neutral FeCl3, a violet color is formed due to the formation of a complex between phenol and FeCl3. On the other hand, when benzoic acid is added to neutral FeCl3, no color change occurs. Therefore, the presence of a violet color indicates the presence of phenol, while the absence of a color change indicates the presence of benzoic acid.

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  • 4. 

    Which of the following acids on heating loses a molecule of H2O to from and α, β-unsaturated acid?

    • CH3CHOHCOOH

    • HOCH2COOH

    • CH3CHOHCH2COOH

    • HOCH2CH2CH2COOH

    Correct Answer
    A. CH3CHOHCH2COOH
    Explanation
    When CH3CHOHCH2COOH is heated, it loses a molecule of H2O to form an α, β-unsaturated acid. This is because the molecule contains a hydroxyl group (OH) attached to a carbon atom adjacent to a carbonyl group (C=O). Upon heating, the hydroxyl group and a hydrogen atom from the adjacent carbon atom combine to form water (H2O), resulting in the formation of a double bond between the two carbon atoms. This double bond creates the α, β-unsaturated acid.

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  • 5. 

    Which of the following compound will have the smallest pKa value?

    • Benzoic acid

    • Formic acid

    • Acetic acid

    • Phenylacetic acid

    Correct Answer
    A. Formic acid
    Explanation
    Formic acid will have the smallest pKa value because it is the strongest acid among the given compounds. The presence of the electron-withdrawing group, the formyl group (-CHO), increases the acidity of formic acid compared to the other compounds. The formyl group can stabilize the negative charge on the conjugate base, making it easier to lose a proton and increasing the acidity of the compound. Therefore, formic acid will have the smallest pKa value.

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  • 6. 

    When CH2 = CH–COOH is reduced with LiAlH4, the compound obtained will be:

    • CH3–CH2–CHO

    • Aldehydes, Ketones & Carboxylic Acids - Quiz

    • CH2–CH–CH2OH

    • CH3–CH2–COOH

    Correct Answer
    A. CH2–CH–CH2OH
    Explanation
    When CH2 = CH–COOH is reduced with LiAlH4, the compound obtained will be CH2–CH–CH2OH. Reduction with LiAlH4 converts the carboxylic acid functional group (–COOH) into an alcohol functional group (–CH2OH), resulting in the formation of CH2–CH–CH2OH.

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  • 7. 
    Identify the product Y in the following reaction sequence: - ProProfs

    Identify the product Y in the following reaction sequence:

    • Pentane

    • Cyclobutane

    • Cyclopentane

    • Cyclopentanone

    Correct Answer
    A. Cyclopentane
    Explanation
    The given reaction sequence starts with pentane, which is a hydrocarbon with five carbon atoms. It then undergoes a series of reactions, resulting in the formation of cyclobutane, cyclopentane, and finally cyclopentanone. The product Y in this reaction sequence is cyclopentane, which is a cyclic hydrocarbon with five carbon atoms.

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  • 8. 

    Ozonolysis of an organic compound gives formaldehyde as one of the products. This confirms the presence of:

    • A vinyl group

    • An isopropyl group

    • An acetylene triple bond

    • Two ethylenic double bonds

    Correct Answer
    A. A vinyl group
    Explanation
    Ozonolysis is a reaction that involves the cleavage of carbon-carbon double bonds. When ozonolysis of an organic compound gives formaldehyde as one of the products, it confirms the presence of a vinyl group. A vinyl group is a functional group consisting of a carbon-carbon double bond attached to an alkyl group. The formation of formaldehyde suggests that the organic compound contains a vinyl group, which is consistent with the given information.

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  • 9. 

    Which of the following combination of aldehydes gives cross Cannizzaro reaction?

    • CH3CHO, HCHO

    • C6C5CHO, CH3CHO

    • C6C5CHO, HCHO

    • All of these

    Correct Answer
    A. C6C5CHO, HCHO
    Explanation
    The cross Cannizzaro reaction is a reaction where one aldehyde acts as the reducing agent and the other aldehyde acts as the oxidizing agent. In this reaction, the aldehyde that acts as the reducing agent is oxidized to a carboxylic acid, while the aldehyde that acts as the oxidizing agent is reduced to an alcohol. In the given options, only the combination of C6C5CHO and HCHO involves two different aldehydes, making it the correct combination for the cross Cannizzaro reaction.

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  • 10. 

    The dipole moment is the highest for

    • Trans-2-butene

    • 1, 3-dimethylbenzene

    • Acetophenone

    • Ethanol

    Correct Answer
    A. Acetophenone
    Explanation
    Acetophenone has the highest dipole moment because it has a polar carbonyl group (C=O) which creates a significant difference in electronegativity between the carbon and oxygen atoms. This leads to a separation of charge and the formation of a dipole moment. In contrast, trans-2-butene and ethanol do not have such polar groups, while 1,3-dimethylbenzene lacks any functional groups that would contribute to a dipole moment. Therefore, acetophenone has the highest dipole moment among the given options.

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  • 11. 
    Consider The correct decreasing order of their reactivity towards hydrolysis is: - ProProfs

    Consider The correct decreasing order of their reactivity towards hydrolysis is:

    • (ii) > (iv) > (i) > (iii)

    • (ii) > (iv) > (iii) > (i)

    • (i) > (ii) > (iii) > (iv)

    • (iv) > (ii) > (i) > (iii)

    Correct Answer
    A. (ii) > (iv) > (i) > (iii)
    Explanation
    The correct order of reactivity towards hydrolysis is (ii) > (iv) > (i) > (iii). This means that compound (ii) is the most reactive towards hydrolysis, followed by compound (iv), then compound (i), and finally compound (iii).

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  • 12. 

    If the enolate ion combines with the carbonyl group of an ester, we get:

    • Aldol

    • α, β-unsaturated ester

    • β-ketoaldehyde

    • Acid

    Correct Answer
    A. β-ketoaldehyde
    Explanation
    When the enolate ion combines with the carbonyl group of an ester, the resulting product is a β-ketoaldehyde. This is because the enolate ion adds to the carbonyl carbon of the ester, creating a new carbon-carbon bond and forming a β-ketoaldehyde. This reaction is known as the Claisen condensation and is commonly used in organic synthesis to create β-ketoaldehydes.

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  • 13. 

    Which of the following on heating with aqueous KOH, produces acetaldehyde:

    • CH3CH2Cl

    • CH2Cl.CH2Cl

    • CH3CHCl2

    • CH3COCl

    Correct Answer
    A. CH3CHCl2
    Explanation
    When CH3CHCl2 is heated with aqueous KOH, it undergoes a nucleophilic substitution reaction known as dehydrohalogenation. In this reaction, one chlorine atom is replaced by a hydroxyl group (-OH), resulting in the formation of acetaldehyde (CH3CHO).

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  • 14. 

    Which one of the following pairs gives effervescence with aq. NaHCO3? I. CH3COCl II. CH3COCH3 III. CH3COOCH3 IV. CH3CO.O.COCH3

    • I and II

    • I and IV

    • II and III

    • I and III

    Correct Answer
    A. I and IV
  • 15. 
    - ProProfs

    Correct Answer
    A.

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  • Current Version
  • Mar 21, 2023
    Quiz Edited by
    ProProfs Editorial Team
  • Jan 29, 2014
    Quiz Created by
    Tanmay Shankar

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