Every Book Back multiple-choice question from Carbonyl Compounds and Carboxylic Acids (12th Standard Chemistry, Samacheer Kalvi) — each with the correct option highlighted and a clear, worked explanation. Free to read in English and Tamil.
Q1
The correct structure of the product 'A' formed in the reaction (NEET)
[Figure]
is
- A. (figure A)
- B. (figure B)Correct
- C. (figure C)
- D. (figure D)
Explanation. Catalytic reduction using hydrogen gas and a palladium catalyst effectively reduces the carbonyl group of a ketone into a secondary alcohol group without affecting the stable aromatic system.
Q2
The formation of cyanohydrin from acetone is an example of
- A. nucleophilic substitution
- B. electrophilic substitution
- C. electrophilic addition
- D. nucleophilic additionCorrect
Explanation. The cyanide ion acts as a nucleophile that attacks the electron-deficient carbonyl carbon of acetone, resulting in an addition reaction that forms acetone cyanohydrin.
Q3
Reaction of acetone with one of the following reagents involves nucleophilic addition followed by elimination of water. The reagent is
- A. Grignard reagent
- B. Sn / HCl
- C. hydrazine in presence of slightly acidic solutionCorrect
- D. hydrocyanic acid
Explanation. Reactions of ketones with ammonia derivatives such as hydrazine proceed by an initial nucleophilic addition to the carbonyl group followed by the loss of a water molecule to form hydrazones.
Q4
In the following reaction,
HC ≡ CH (H2SO4 / HgSO4) -> X
Product 'X' will not give
- A. Tollen's test
- B. Victor meyer testCorrect
- C. Iodoform test
- D. Fehling solution test
Explanation. The hydration of acetylene produces acetaldehyde. Acetaldehyde gives positive results for Tollen's, Fehling's, and iodoform tests, but the Victor Meyer test is used to identify alcohols, not aldehydes.
Q5
CH2 = CH2 i) O3 ii) Zn / H2O -> X (NH3) -> Y. 'Y' is
- A. Formaldelyde
- B. di acetone ammonia
- C. hexamethylene tetraamineCorrect
- D. oxime
Explanation. Reductive ozonolysis of ethene yields formaldehyde. Formaldehyde reacts with ammonia to form hexamethylenetetraamine, also known as urotropine.
Q6
Predict the product Z in the following series of reactions
Ethanoic acid (PCl5) -> X (C6H6 / Anhydrous AlCl3) -> Y (i. CH3MgBr, ii. H3O+) -> Z.
- A. (CH3)2 C(OH)C6H5Correct
- B. CH3 CH(OH)C6H5
- C. CH3 CH(OH)CH2 - CH3
- D. CH2 - OH
Explanation. Ethanoic acid yields acetyl chloride, which reacts with benzene to form acetophenone. Acetophenone then reacts with methyl magnesium bromide to produce 2-phenylpropan-2-ol after hydrolysis.
Q7
Assertion: 2,2 – dimethyl propanoic acid does not give HVZ reaction.
Reason: 2 – 2, dimethyl propanoic acid does not have alpha - hydrogen atom
- A. if both assertion and reason are true and reason is the correct explanation of assertion.Correct
- B. if both assertion and reason are true but reason is not the correct explanation of assertion.
- C. assertion is true but reason is false
- D. both assertion and reason are false.
Explanation. The Hell-Volhard-Zelinsky reaction specifically targets alpha-hydrogen atoms for substitution by halogens. Since 2,2-dimethylpropanoic acid lacks any alpha-hydrogens, the reaction cannot occur.
Q8
Which of the following represents the correct order of acidity in the given compounds
- A. FCH2COOH > CH3COOH > BrCH2COOH > ClCH2COOH
- B. FCH2COOH > ClCH2COOH > BrCH2COOH > CH3COOHCorrect
- C. CH3COOH > ClCH2COOH > FCH2COOH > BrCH2COOH
- D. ClCH2COOH > CH3COOH > BrCH2COOH > ICH2COOH
Explanation. The acidity increases with the inductive effect of halogen substituents. Fluoroacetic acid is the strongest due to fluorine's high electronegativity, followed by chloro, then bromo, with ethanoic acid being the weakest.
Q9
Benzoic acid i) NH3/heat -> A (NaOBr) -> B (NaNO2 / HCl) -> C (H2O) -> D. 'C' is
- A. anilinium chloride
- B. O – nitro aniline
- C. benzene diazonium chlorideCorrect
- D. m – nitro benzoic acid
Explanation. Benzoic acid is converted to benzamide and then to aniline through Hofmann degradation. Aniline reacts with sodium nitrite and hydrochloric acid to form benzene diazonium chloride.
Q10
Ethanoic acid (P / Br2) -> 2 – bromoethanoic acid. This reaction is called
- A. Finkelstein reaction
- B. Haloform reaction
- C. Hell – Volhard – Zelinsky reactionCorrect
- D. none of these
Explanation. The direct halogenation of carboxylic acids at the alpha position using red phosphorus and a halogen is known as the Hell-Volhard-Zelinsky reaction.
Q11
CH3Br (KCN) -> (A) (H3O+) -> (B) (PCl5) -> (C). product (C) is
- A. acetylchlorideCorrect
- B. chloro acetic acid
- C. alpha- chlorocyano ethanoic acid
- D. none of these
Explanation. Starting with methyl bromide, reaction with cyanide yields methyl cyanide. Hydrolysis gives ethanoic acid, which reacts with phosphorus pentachloride to form acetyl chloride.
Q12
Which one of the following reduces tollens reagent
- A. formic acidCorrect
- B. acetic acid
- C. benzophenone
- D. none of these
Explanation. Formic acid uniquely contains an aldehyde-like hydrogen-carbonyl bond, which allows it to behave as a reducing agent and reduce ammoniacal silver nitrate to metallic silver.
Q13
- A. (figure A)
- B. (figure B)Correct
- C. (figure C)
- D. (figure D)
Explanation. The reaction of a Grignard reagent with carbon dioxide followed by acid hydrolysis yields a carboxylic acid.
Q14
The IUPAC name of the following structure is:
- A. but – 3- enoicacidCorrect
- B. but – 1- ene-4-oicacid
- C. but – 2- ene-1-oic acid
- D. but -3-ene-1-oicacid
Explanation. In naming carboxylic acids, the carbon chain is numbered starting from the carboxyl carbon. This four-carbon chain contains a double bond beginning at the third position.
Q15
Identify the product formed in the following reaction:
- A. (figure A)
- B. (figure B)
- C. (figure C)
- D. (figure D)Correct
Explanation. The reagents hydrazine and sodium ethoxide represent the Wolff-Kishner reduction, which converts a carbonyl group into a methylene group.
Q16
In which case chiral carbon is not generated by reaction with HCN?
- A. (figure A)Correct
- B. (figure B)
- C. (figure C)
- D. (figure D)
Explanation. A chiral carbon is not generated if the starting carbonyl compound is symmetrical, as the resulting tetrahedral carbon will have two identical groups.
Q17
Assertion : p – N, N – dimethyl aminobenzaldehyde undergoes benzoin condensation
Reason : The aldehydic (-CHO) group is meta directing
- A. if both assertion and reason are true and reason is the correct explanation of assertion.
- B. if both assertion and reason are true but reason is not the correct explanation of assertion.Correct
- C. assertion is true but reason is false
- D. both assertion and reason are false.
Explanation. Both statements are correct observations. However, the electrophilic substitution directing property of the aldehyde group does not provide the mechanistic explanation for its behavior in the nucleophilic benzoin condensation.
Q18
Which one of the following reaction is an example of disproportionation reaction?
- A. Aldol condensation
- B. cannizaro reactionCorrect
- C. Benzoin condensation
- D. none of these
Explanation. In a Cannizzaro reaction, two molecules of an aldehyde are simultaneously oxidized and reduced, fitting the definition of disproportionation.
Q19
Which one of the following undergoes reaction with \(50\%\) sodium hydroxide solution to give the corresponding alcohol and acid?
- A. PhenylmethanalCorrect
- B. ethanal
- C. ethanol
- D. methanol
Explanation. Aldehydes lacking alpha-hydrogen atoms undergo the Cannizzaro reaction. Phenylmethanal is an aromatic aldehyde that produces benzyl alcohol and sodium benzoate under these concentrated basic conditions.
Q20
The reagent used to distinguish between acetaldehyde and benzaldehyde is:
- A. Tollens reagent
- B. Fehling’s solutionCorrect
- C. 2,4 – dinitrophenyl hydrazine
- D. semicarbazide
Explanation. Fehling's solution reacts with aliphatic aldehydes to give a characteristic red precipitate but does not react with aromatic aldehydes like benzaldehyde.
Q21
Phenyl methanal is reacted with concentrated NaOH to give two products X and Y. X reacts with metallic sodium to liberate hydrogen. X and Y are:
- A. sodiumbenzoate and phenol
- B. Sodium benzoate and phenyl methanol
- C. phenyl methanol and sodium benzoateCorrect
- D. none of these
Explanation. The products of the Cannizzaro reaction of phenylmethanal are phenylmethanol and sodium benzoate. Phenylmethanol is an alcohol that reacts with sodium to release hydrogen gas.
Q22
In which of the following reactions new carbon – carbon bond is not formed?
- A. Aldol condensation
- B. Friedel craft reaction
- C. Kolbe’s reaction
- D. Wolf kishner reductionCorrect
Explanation. Wolff-Kishner reduction replaces the oxygen of a carbonyl group with hydrogen atoms, reducing the functional group without building onto the existing carbon skeleton.
Q23
An alkene “A” on reaction with \(O_3\) and \(Zn - H_2O\) gives propanone and ethanal in equimolar ratio. Addition of HCl to alkene “A” gives “B” as the major product. The structure of product “B” is:
- A. (figure A)
- B. (figure B)
- C. (figure C)Correct
- D. (figure D)
Explanation. Ozonolysis products help identify the starting alkene structure. Addition of HCl follows Markovnikov's rule, where the chloride adds to the more substituted carbon of the double bond.
Q24
Carboxylic acids have higher boiling points than aldehydes, ketones and even alcohols of comparable molecular mass. It is due to their:
- A. more extensive association of carboxylic acid via van der Waals force of attraction
- B. formation of carboxylate ion
- C. formation of intramolecular H-bonding
- D. formation of intermolecular H – bondingCorrect
Explanation. Carboxylic acids exhibit extensive intermolecular hydrogen bonding, often forming stable dimers that require more energy to vaporize compared to other carbonyl compounds.
