JEE Chemistry Aldehydes Ketones and Carboxylic Acids MCQs Set C

Question. Which of the following is the correct decreasing order of acidic strength of
(i) Methanoic acid  (ii) Ethanoic acid
(iii) Propanoic acid (iv) Butanoic acid
(a) (i) > (ii) > (iii) > (iv)
(b)   (i) > (iv) > (iii) > (ii)
(c) (ii) > (iii) > (iv) > (i)
(d) (iv) > (i) > (iii) > (ii)

Answer: A

Question. Among the following the strongest acid is
(a) CH₂ClCOOH
(b) CH₃COOH
(c) CH₃CH₂COOH
(d) None of these

Answer: A

Question. Read the following statements and choose the correct option
(i) The carbonyl carbon atom is sp² -hybridised
(ii) The carbonyl carbon is an electrophilic (Lewis acid) centre
(iii) The carbonyl oxygen is a nucleophilic (Lewis base) centre
(iv) Carbonyl compounds are non- polar in nature.
(a)   (i), (ii) and (iii) are correct
(b) (ii), (iii) and (iv) are correct
(c) (ii) and (iv) are correct
(d) (i), (ii) and (iv) are correct

Answer: A

Question. Which of the following statement(s) is/are true regarding preparation of aldehydes and ketones?
(i) Both can be prepared by the oxidation of the concerned alcohol with copper at about 250ºC.
(ii) Both can be prepared by the oxidation of the concerned alcohol by Oppenauer oxidation.
(iii) Both can be prepared by the oxidation of respective alcohol with acidic dichromate.
(a) (i) only
(b) (i) and (iii)
(c) (ii) and (iii)
(d) All the three

Answer: A

Question. Which of the following statements are false?
(i) No aldehyde can be prepared by the oxidation of primary alcohol with acidic KMnO₄.
(ii) Aldehydes having a boiling point less than 100°C can be prepared by the oxidation of primary alcohol with acidic dichromate.
(iii) Secondary alcohols on oxidation with PCC in dichloromethane give carboxylic acids having lesser number of carbon atoms
(iv) Tertiary alcohols can't be oxidised at all
(a) (i), (iii) and (iv)
(b) (ii) and (iii)
(c) (ii), (iii) and (iv)
(d) (i), (ii) and (iii)

Answer: A

Question. Read the following statements and choose the correct option
(i) The boiling points of aldehydes and ketones are lower than those of alcohols of similar molecular masses
(ii) Alcohols show intermolecular hydrogen bonding whereas aldehydes and ketones do not show intermolecular hydrogen bonding.
(iii) The lower members of aldehydes and ketones are miscible with water in all proportions, because they form hydrogen bond with water.
(iv) The solubility of aldehydes and ketones increases rapidly on increasing the length of alkyl chain.
(a) TTTF
(b) TFFT
(c) TTFF
(d) FTTT

Answer: A

Question. Aldehydes are generally more reactive than ketones in nucleophilic addition reactions. Which of the following statements accounts for this ?
(i) Sterically, the presence of two relatively large substituents in ketones hinders the approach of nucleophile to carbonyl carbon
(ii) Aldehydes show resonance whereas ketones do not
(iii) Electronically, the presence of two alkyl groups reduce the electrophilicity of the carbonyl carbon more effectively.
(iv) Electronically carbonyl carbon atom in ketones is more electrophilic than in aldehydes
(a) (i) and (iii)
(b) (ii) and (iii)
(c) (i) and (iv)
(d) (ii) and (iv)

Answer: A

Question. Which of the following statement(s) is/are true regarding esterification of a carboxylic acid with an alcohol ?
(i) It is carried out in presence of a strong acid which acts as a catalyst.
(ii) The strong acid makes the carbonyl carbon more electrophilic, and hence causes the alcohol, a strong nucleophile to attack on the carbonyl carbon.
(iii) The strong acid makes the carbonyl group more electrophilic which is thus attacked easily by an alcohol, a weak nucleophile.
(iv) Esterification can be done even in absence of a strong acid.
(a) (i) and (iii)
(b) (iv) only
(c) (i) and (ii)
(d) (i) only

Answer: A

Question.
Assertion : The boiling points of aldehydes and ketones are higher than hydrocarbons and ethers of comparable molecular masses.
Reason : There is a weak molecular association in aldehydes and ketones arising out of the dipole-dipole interactions.
(a) Assertion is correct, reason is correct; reason is a correct explanation for assertion
(b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(c) Assertion is correct, reason is incorrect
(d) Assertion is incorrect, reason is correct

Answer: A

Question.
Assertion : Formaldehyde is a planar molecule.
Reason : It contains sp² hybridised carbon atom
(a) Assertion is correct, reason is correct; reason is a correct explanation for assertion
(b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(c) Assertion is correct, reason is incorrect
(d) Assertion is incorrect, reason is correct

Answer: A

Question.
Assertion : Compounds containing –CHO group are easily oxidised to corresponding carboxylic acids.
Reason : Carboxylic acids can be reduced to alcohols by treatment with LiAlH₄.
(a) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(b) Assertion is correct, reason is incorrect
(c) Assertion is incorrect, reason is correct
(d) Assertion is correct, reason is correct; reason is a correct explanation for assertion

Answer: A

Question.
Assertion : The molecular mass of acetic acid in benzene is 120 instead of 60.
Reason : The carboxylic acids exist as cyclic dimers in which the two molecules of the acid are held together by two strong hydrogen bonds
(a) Assertion is correct, reason is correct; reason is a correct explanation for assertion
(b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(c) Assertion is correct, reason is incorrect
(d) Assertion is incorrect, reason is correct

Answer: A

Question. Which of the following reagent reacts in different ways with CH₃CHO, HCHO and C₆H₅CHO ?
(a) Ammonia
(b) Fehling solution
(c) HCl
(d) None of these

Answer: A

Question. A new carbon - carbon bond is formed in
(i) Aldol condensation (ii) Kolbe’s reaction
(iii) Reimer-Tiemann reaction
(iv) Wurtz Fittig reaction
(a) All the four
(b) (ii) and (iii)
(c) (i) and (iii)
(d) (i), (ii) and (iiv)

Answer: A

Question. In the crossed Cannizzaro reaction involving HCHO as one of the components
(a) both of the above statements are true
(b) none of the above statement is true
(c) HCHO is always oxidised because of steric effect
(d) HCHO is always oxidised because of electronic effect

Answer: A

Question. When ethanal reacts with propanal in the presence of a base, the number of products formed is
(a) 4
(b) 2
(c) 3
(d) 5

Answer: A

Question. Aldehydes and ketones will not form crystalline derivatives with
(a) dihydrogen sodium phosphate
(b) semicarbazide hydrochloride
(c) phenylhydrazine
(d) sodium bisulphite

Answer: A

Question. Which of the following compound will undergo self aldol condensation in the presence of cold dilute alkali ?
(a) CH₃CH₂CHO
(b) C₆H₅CHO
(c) Both
(d) None of these

Answer: A

Question. An organic compound of formula, C₃H₆O forms phenyl hydrazone, but gives negative Tollen’s test. The compound is
(a) Both
(b) CH₃CH₂COCH₃
(c) CH₃COCH₃
(d) None of these

Answer: A

Question. Benzophenone can be obtained by_____________.
(i) Benzoyl chloride + Benzene + AlCl₃
(ii) Benzoyl chloride + Diphenyl cadmium
(iii) Benzoyl chloride + Phenyl magnesium chloride
(iv) Benzene + Carbon monoxide + ZnCl₂
(a) (i), (ii) and (iii)
(b) (iii) and (iv)
(c) (ii) and (iii)
(d) (i), (ii) and (iv)

Answer: C

Question. Which of the following conversions can be carried out by Clemmensen Reduction ?
(i) Benzaldehyde into benzyl alcohol
(ii) Cyclohexanone into cyclohexane
(iii) Benzoyl chloride into benzaldehyde
(iv) Benzophenone into diphenyl methane
(a) (ii) and (iv)
(b) (i) and (iii)
(c) (i) and (iv)
(d) (iii) and (iv)

Answer: A

Question. Benzaldehyde is less reactive than propanal because
(i) the carbon atom of the carbonyl group of benzaldehyde is less electrophilic as in propanal.
(ii) the carbon atom of the carbonyl group of benzaldehyde is more electrophilic as in propanal.
(iii) carbonyl group in benzaldehyde is more polar due to resonance
(iv) carbonyl group in benzaldehyde is less polar due to resonance
(a) (i) and (iv)
(b) (iv) only
(c) (i) and (iii)
(d) None of these

Answer: A

Question. Addition of alcohols to aldehydes and ketones takes place in presence of dry HCl gas because it
(i) Protonates the oxygen of the carbonyl compounds
(ii) Increases the electrophilicity of the carbonyl carbon
(iii) Removes the excess moisture from the reaction
(iv) Helps the reaction to move in the forward direction
(a) (i), (ii), (iii) and (iv)
(b) (i), (iii) and (iv)
(c) (i), (ii) and (iv)
(d) (ii) ,(iii), and (iv)

Answer: A

Question. Addition of hydrogen cyanide to aldehydes and ketones occurs in presence of a base.The role of base is to
(i) catalyse the reaction
(ii) generate CN^– ion
(iii) slow down the reaction
(iv) to stabilize the cyanohydrins
(a) (i) and (ii)
(b) (ii) and (iv)
(c) (i) and (iii)
(d) (i) and (iv)

Answer: A

Question. When benzaldehyde and acetaldehyde undergoes reaction with the 2, 4–DNP ?
(a) Benzaldehyde reacts slowly than acetaldehyde
(b) Acetaldehyde reacts slowly than benzaldehyde
(c) Both reacts equally
(d) Both do not react with 2, 4-DNP

Answer: A

Question. Suppose the reaction of compound containing ketone as functional group is carried in basic medium of NaOH. Which of the following will one use to protect the unwanted reaction due presence of carbonyl moiety.
(a) ethylene glycol and HCl
(b) HCN
(c) NaHSO₃
(d) None of these

Answer: A

Question. A compound C₅H₁₀O forms orange–red precipitate upon reaction with 2,4–DNP, but does not give positive Tollen’s test and iodoform test. Possible compound is
(a) Pentan–3–one
(b) 2, 2–dimethylpropanal
(c) 3–methylbutan–2–one
(d) None of the above

Answer: A

Question. Nitration of the compound is carried out, this compound gives red–orange ppt. with 2,4–DNP, this compound undergoes Cannizzaro reaction but not aldol, than possible product due to nitration is
(a) 3–nitrobezaldehyde
(b) None of these
(c) (2–nitro)–2–phenylethanal
(d) 3–nitroacetophenone

Answer: A

Question. An organic compound A upon reacting with NH₃ gives B. On heating B gives C. C in presence of KOH reacts with Br2 to given CH₃CH₂NH₂. A is
(a) CH₃CH₂COOH
(b) CH₃CH₂CH₂COOH
(c) CH₃COOH
(d) None of these

Answer: A

Question. Through which of the following reactions number of carbon atoms can be increased in the chain?
(i) Grignard reaction      (ii) Cannizzaro’s reaction
(iii) Aldol condensation (iv) HVZ reaction
Choose the correct option.
(a) Only (iii) and (i)
(b) Only (iii) and (iv)
(c) Only (iii) and (ii)
(d) (i), (ii), (iii) and (iv)

Answer: A