HOTs Aldehydes Ketones and Carboxylic Acids Class 12 Chemistry

Please refer to Aldehydes Ketones and Carboxylic Acids HOTs Class 12 Chemistry provided below with Aldehydes Ketones and Carboxylic Acids. All HOTs for Class 12 Chemistry with answers provided below have been designed as per the latest syllabus and examination petter issued by CBSE, NCERT, KVS. Students of Standard 12 Chemistry should learn the solved HOTS for Class 12 Chemistry provided below to gain better marks in examinations.

Aldehydes Ketones and Carboxylic Acids Class 12 Chemistry HOTs

Question. Boiling points of carboxylic acids are
(a) lower than corresponding alcohols
(b) higher than corresponding alcohols
(c) equal to that of corresponding alcohols
(d) None of the above

Question. Which reaction is used for detecting the presence of carbonyl group?
(a) Reaction with hydrazine
(b) Reaction with phenyl hydrazine
(c) Reaction with hydroxylamine
(d) All of the above

Question. In the anion HCOO– the two carbon-oxygen bonds are found to be of equal length. What is the reason for it?
(a) Electronic orbitals of carbon atom are hybridised
(b) The C=O bond is weaker than the C–C bond
(c) The anion HCOO– has two reasonating structures
(d) The anion is obtained by removal of a proton from the acid molecule

Question. Two compounds benzyl alcohol and benzoic acid are formed from this compound, when this compound is heated in the presence of conc.NaOH, this compound is.
(a) Benzaldehyde
(b) Benzylalcohol
(c) Acetophenone
(d) Benzophenone

Question. Select the acid(s) which cannot be prepared by Grignard reagent.
(a) Acetic acid
(b) Succinic acid
(c) Formic acid
(d) All of the above

Question. In the reaction

Question. Carboxylic acids are more acidic than phenol and alcohol because of
(a) intermolecular hydrogen bonding
(b) formation of dimers
(c) highly acidic hydrogen
(d) resonance stabilization of their conjugate base

Question. Which of the following acids has the smallest dissociation constant ?
(a) CH₃CHFCOOH
(b) FCH₂CH₂COOH
(c) BrCH₂CH₂COOH
(d) CH₃CHBrCOOH

Question.

Question. The major product of nitration of benzoic acid is
(a) 3- Nitrobenzoic acid
(b) 4- Nitrobenzoic acid
(c) 2- Nitrobenzoic acid
(d) 2, 4- dinitrobenzoic acid

Question. Among the following acids which has the lowest pKa value?
(a) CH₃CH₂COOH
(b) (CH₃)₂CH — COOH
(c) HCOOH
(d) CH₃COOH

Question. Wolf-Kishner reduction is
(a) reduction of carbonyl compound into alcohol
(b) reduction of carbonyl compound into alkene
(c) reduction of carboxyl compound into alkane
(d) reduction of nitro compound into aniline

Question.

Question. Which is false in case of carboxylic acids?
(a) They are polar molecules
(b) They form H-bonds
(c) They are stronger than mineral acids
(d) They have higher b.p. than corresponding alcohols

Question. During reduction of aldehydes with hydrazine and potassium hydroxide, the first step is the formation of

Question. Which of the following is the weakest acid ?

Question. Acetic anhydride is obtained by the reaction of
(a) sodium and acetic acid
(b) ammonia and acetic acid
(c) ethanol and acetic acid
(d) P₂O₅ and acetic acid

Question. Toluene can be oxidised to benzoic acid by
(a) KMnO₄ (alk.)
(b) K₂Cr₂O₇ (alk.)
(c) Both (a) and (b)
(d) Neither (a) nor (b)

Question. Propionic acid with Br₂/P yields a dibromo product. Its structure would be:

Question. Which of the following compounds will give butanone on oxidation with alkaline KMnO₄ solution?
(a) Butan-1-ol
(b) Butan-2-ol
(c) Both of these
(d) None of these

Question. The reaction of carboxylic acid gives effervescences of CO₂ with NaHCO₃. The CO₂ comes from.
(a) R – COOH
(b) NaHCO₃
(c) Both (a) and (b)
(d) None of these

Question. Benzoic acid reacts with conc. HNO₃ and H₂SO₄ to give :
(a) 3-Nitrobenzoic acid
(b) 4-Benzene sulphonic acid
(c) 4-Nitrobenzoic acid
(d) 2-Nitrobenzoic acid

Question. Lower carboxylic acids are soluble in water due to
(a) low molecular weight
(b) hydrogen bonding
(c) dissociation into ions
(d) easy hydrolysis

Question. Dimerisation of carboxylic acids is due to
(a) ionic bond
(b) covalent bond
(c) coordinate bond
(d) intermolecular hydrogen bond

Question. A carboxylic acid can best be converted into acid chloride by using
(a) PCl₅
(b) SOCl₂
(c) HCl
(d) ClCOCOCl

Question. Arrange the following four acids in their decreasing order of acidity

(a) I > II > III > IV
(b) IV > III > II > I
(c) II > IV > III > I
(d) III > IV > II > I

Question.The strongest acid among the following is –
(a) Salicylic acid
(b) m-hydroxybenzoic acid
(c) p-hydroxybenzoic acid
(d) Benzoic acid

Question. Among the following, the most acidic is :
(a) CH₃COOH
(b) ClCH₂COOH
(c) Cl₂CHCOOH
(d) Cl₂CHCH₂COOH

Question. The elimination of CO₂ from a carboxylic acid is known as
(a) hydration
(b) dehydration
(c) decarboxylation
(d) carboxylation

STATEMENT TYPE QUESTIONS

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) TTFF
(b) TFFT
(c) FTTT
(d) TTTF

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) (ii) and (iii)
(b) (ii), (iii) and (iv)
(c) (i), (iii) and (iv)
(d) (i), (ii) and (iii)

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 (iv) are correct
(b) (i), (ii) and (iii) are correct
(c) (ii), (iii) and (iv) are correct
(d) (ii) and (iv) are correct

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 (ii)
(b) (i) and (iii)
(c) (i) only
(d) (iv) only

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) (ii) and (iii)
(c) (i) and (iii)
(d) All the three

Question.

Which of the following statements are correct regarding the above reduction of benzaldehyde to benzyl alcohol?
(i) One hydrogen is coming from H₂O as H+ and another from C₆H₅CHO as H–
(ii) One hydrogen is coming from H₂O as H– and another from C₆H₅CHO as H+
(iii) One hydrogen from H₂O and another from C₆H₅CHO, both in the form of H–
(iv) The reduction is an example of disproportionation reaction
(a) (i), (ii) and (iii)
(b) (i) and (iv)
(c) (ii), (iii) and (iv)
(d) (iii) and (iv)

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) (i) and (iv)
(c) (ii) and (iii)
(d) (ii) and (iv)

Question. (i) Draw the structures of the following :
(a) p-Methylbenzaldehyde,
(b) 4-Methylpent-3-en-2-one.
(ii) Give chemical tests to distinguish between the following pairs of compounds :
(a) Benzoic acid and Ethyl benzoate,
(b) Benzaldehyde and Acetophenone
(c) Phenol and Benzoic acid.
Answer.

(b) (CH₃)₂C = CHCOCH₃ 
(ii) (a) On adding sodium bicarbonate to benzoic acid, brisk effervescence of CO₂ is evolved.

Whereas ethyl benzoate does not. 
(b) Acetophenone having at least one –CH₃ group on heating with alkaline solution of iodine forms yellow coloured precipitate of iodoform.

Whereas benzaldehyde does not. 
(c) Benzoic acid reacts with NaHCO₃ giving CO₂ gas with effervescence whereas phenol does not.

Question. (a) Draw structures of the following derivatives :
(i) Cyanohydrin of cyclobutanone
(ii) Hemiacetal of ethanal
(b) Write the major product(s) in the following :

(c) How can you distinguish between propanal and propanone? 
Answer. (a) (i) Cyanohydrin of cyclobutanone

(c) By iodoform test : Propanone on treatment with I₂/NaOH undergoes iodoform test to give a yellow ppt. of iodoform.

Propanal does not give this test.

Question. (a) Write the structures of A and B in the following reactions :

(b) Distinguish between :
(i) C₆H₅ – COCH₃ and C₆H₅ – CHO,
(ii) CH₃COOH and HCOOH.
(c) Arrange the following in the increasing order of their boiling points :
CH₃CHO, CH₃COOH, CH₃CH₂OH.
Answer. (a) (i) A : CH₃CHO, B : CH₃CH=N–OH 
(ii) A : CH₃COOH , B : CH3COCl 
(b) (i) Heat both compounds with NaOH and I₂, C₆H₅COCH₃ forms yellow ppt. of CHI₃ whereas C₆H₅CHO does not.
(ii) Add ammonical solution of silver nitrate (Tollens’ reagent) to both the compounds,HCOOH gives silver mirror but CH₃COOH does not.
(c) CH₃CHO < CH₃CH₂OH < CH₃COOH

Question. (i) Write the product(s) in the following reactions:

(ii) Give simple chemical tests to distinguish between the following pairs of compounds:
(a) Ethanol and Phenol
(b) Propanol and 2-methylpropan -2-ol
Answer. (i) (a)

(b) (CH₃)₂ CHOH and CH₃ CH₂I 
(c) CH₃CH=CHCHO 
(ii) (a) Add neutral FeCl₃ to both the compounds, phenol gives violet complex. 
(b) Add anhy ZnCl₂ and conc. HCl to both the compounds, 2-methyl propan-2-ol gives turbidity immediately.

Question. (i) How will you convert:
(a) Benzene to acetophenone
(b) Propanone to 2-Methylpropan-2-ol
(ii) Give reasons:
(a) Electrophilic substitution in benzoic acid take place at meta-position.
(b) Carboxylic acids are higher boiling liquids than aldehydes, ketones and alcohols of comparable molecular masses.
(c) Propanal is more reactive than propanone in nucleophilic addition reactions.
Answer. (i) (a)

(ii) (a) Because it is a deactivating group/due to electron withdrawing carboxylic group resulting in decreased electron density at o- and p- position. 
(b) Due to extensive association of carboxylic acid molecules through intermolecular hydrogen bonding. 
(c) Due to steric and +I effect of two methyl groups in propanone. 

Question. (a) Write the chemical reaction involved in Wolff-Kishner reduction.
(b) Arrange the following in the increasing order of their reactivity towards nucleophilic addition reaction :
C₆H₅COCH₃, CH₃ – CHO, CH₃COCH₃
(c) Why carboxylic acid does not give reactions of carbonyl group ?
(d) Write the product in the following reaction.

(e) A and B are two functional isomers of compound C₃H₆O. On heating with NaOH and I₂, isomer B forms yellow precipitate of iodoform whereas isomer A does not form any precipitate. Write the formulae of A and B.
Answer.

(b) C₆H₅COCH₃ < CH₃COCH₃ < CH₃CHO 
(c) Because of resonance in carboxylic group, the carbonyl group, loses a double bond character.
(d) CH₃CH₂CH=CH–CH₂CHO 
(e) A : CH₃CH₂CHO 
B : CH₃COCH₃

Question. (i) Describe the following giving chemical equations :
(a) Decarboxylation reaction
(b) Friedel-Crafts reaction
(ii) How will you bring about the following conversions ?
(a) Benzoic acid to Benzaldehyde
(b) Benzene to m-Nitroacetophenone
(c) Ethanol to 3-Hydroxybutanal
Answer. (i) (a) Carboxylic acids lose carbon dioxide to form hydrocarbons when their sodium salts are heated with
sodalime (NaOH and CaO).

(b) The alkyl / acyl group is introduced at ortho- and para- positions by reaction of anisole with alkyl halide / acyl halide in the presence of anhydrous aluminium chloride (a Lewis acid) as catalyst.

Question. (i) Complete the following equations :

(ii) Distinguish between :

Answer.

Question. (i) Give reasons :
(a) HCHO is more reactive than CH₃ – CHO towards addition of HCN.
(b) pKa of O₂N – CH₂ – COOH is lower than that of CH₃ – COOH.
(c) Alpha hydrogen of aldehydes and ketones is acidic in nature.
(ii) Give simple chemical tests to distinguish between the following pairs of compounds :
(a) Ethanal and Propanal
(b) Pentan-2-one and Pentan-3-one
Answer. (i) (a) Due to +I effect of methyl group in CH₃CHO. 
(b) Due to –I effect of nitro group in nitroacetic acid. 
(c) Due to the strong electron withdrawing effect of the carbonyl group and resonance stabilisation of the conjugate base. 
(ii) (a) Add NaOH and I₂ to both the compounds and heat, ethanal gives yellow ppt of iodoform. 
(b) Add NaOH and I₂ to both the compounds and heat, pentan-2-one gives yellow ppt of iodoform.

Question. (a) An organic compound (A) having molecular formula C4H8O gives orange red precipitate with 2, 4-DNP reagent. It does not reduce Tollens’ reagent but gives yellow precipitate of iodoform on heating with NaOH and I₂. Compound (A) on reduction with NaBH4 gives compound (B) which undergoes dehydration reaction on heating with conc. H₂SO₄ to form compound (C). Compound (C) on ozonolysis gives two molecules of ethanal.

Identify (A), (B) and (C) and write their structures. Write the reactions of compound
(A) with (i) NaOH/I₂ and (ii) NaBH4.
(b) Give reasons :
(i) Oxidation of propanal is easier than propanone.
(ii) a-hydrogen of aldehydes and ketones is acidic in nature.
Answer. (a) Compound A (C₄H₈O) gives positive, 2, 4-DNP test, it must be carbonyl compound. It gives iodoform test.

(b) (i) Oxidation of propanal is easier than propanone because aldehydes have one hydrogen atom attached to the carbonyl group while ketones have two alkyl or aryl groups attached to the carbonyl group. Propanal easily oxidised to form acid with same number of carbon atoms whereas propanone is difficult to be oxidise and form acids with less number of carbon atoms.

(ii) a-hydrogen of aldehydes and ketones are acidic in nature because carbonyl group has the great electron withdrawing effect and the molecule thus formed after the removal of a-Hydrogen is resonance stabilised.

Question. (i) Write the products of the following reaction:

(ii) Write simple chemical tests to distinguish between the following pairs of compounds ?
(a) Propanal and propanone
(b) Benzaldehyde and Benzoic acid
Answer. (i) (a)

(b) CH₃COOH
(c) CH₃ — CH(Br)— COOH
(ii) (a) Add ammonical solution of silver nitrate / Tollen’s reagent to both the compounds, propanal will give silver mirror while propanone does not. 
(b) Add NaHCO₃ solution to both the compounds, benzoic acid will give effervescence and liberate CO₂ while benzaldehyde will not. 

Question. (i) Give a plausible explanation for each one of the following :
(a) Although phenoxide ion has more number of resonating structures than carboxylate ion, carboxylic acid is a stronger acid than phenol.
(b) There are two -NH₂ groups in semicarbazide.
However, only one is involved in the formation of semicarbazones.
(ii) Carry out the following conversions in not more than two steps :
(a) Phenyl magnesium bromide to benzoic acid.
(b) Acetaldehyde to But-2-enal.
(c) Benzene to m-Nitroacetophenone.
Answer.
(b) Semicarbazide has two —NH₂ groups.
One of them, which is directly attached to

is involved in resonance. Thus, electron density on this group decreases and it does not act as a nucleophile. In contrast, the lone pair of electrons on the other —NH₂ group is available for nucleophilic attack.

Question. Write the structures of A, B, C, D and E in the following reactions :

Answer. A-C₆H₅COCH₃ 
B-C₆H₅CH₂CH₃ 
C-C₆H₅COOH
D ,E -C6H5COONa, CHI₃

Question. An aromatic compound ‘A‘ of molecular formula C₇H₆O₂ undergoes a series of reactions as shown below.
Write the structures of A, B, C, D and E in the following reactions :

Answer.

Question. (i) Account for the following :
(a) Propanal is more reactive than propanone towards nucleophilic reagents.
(b) Electrophilic substitution in benzoic acid takes place at meta-position.
(c) Carboxylic acids do not give characteristic reactions of carbonyl group.
(ii) Give simple chemical test to distinguish between the following pairs of compounds:
(a) Acetophenone and benzaldehyde
(b) Benzoic acid and ethylbenzoate
Answer. (i) (a) Due to steric and +I effect of two methyl groups in propanone. 
(b) Because it is a deactivating group/due to electron withdrawing carboxylic group resulting in decreased electron density at o- and p- position.
(c) Due to resonance, electrophilicity of carbonyl carbon is reduced. 
(ii) (a) Add NaOH and I₂ to both the compounds and heat, acetophenone forms yellow ppt of iodoform. 
(b) Add NaHCO₃ solution to both the compounds, benzoic acid will give effervescence and liberates CO₂.

Question. (a) Write the chemical equation for the reaction involved in Cannizzaro reaction.
(b) Draw the structure of the semicarbazone of ethanal.
(c) Why pKa of F – CH₂ – COOH is lower than that of Cl – CH₂ – COOH ?
(d) Write the product in the following reaction

(e) How can you distinguish between propanal and propanone ?

Answer.

(or any other example) 
(b) CH₃CH=N–NHCONH₂ 
(c) Stronger -I effect of fluorine, stronger acid less pka / strong electron withdrawing power of fluorine. 
(d) CH₃CH=CHCH₂ CHO
(e) Silver mirror formed on adding ammonical silver nitrate to propanal and not with propanone.

Question. (i) Write structures of A, B, C and D in the following reaction sequence:

(ii) Arrange the following compounds in the increasing order of their boiling points :
CH₃CHO, CH₃CH₂OH, CH₃OCH₃, CH₃COOH
Answer. (i) A: CH₃CHO; B: CH₃-CH(OH)-CH₂-CHO;
C: CH₃-CH=CH-CHO; D: CH₃-CH(CH₃)-OH 1x₄
(ii) CH₃-O-CH₃<CH₃CHO<CH₃-CH₂-OH < CH₃-COOH

Question. (a) Write the reactions involved in the following :
(i) Etard reaction (ii) Stephen reduction
(b) How will you convert the following in not more than two steps :
(i) Benzoic acid to benzaldehyde
(ii) Acetophenone to benzoic acid
(iii) Ethanoic acid to 2-hydroxyethanoic acid 
Answer.

Question. (i) Write the products of the following reactions :

(ii) Give simple chemical tests to distinguish between the following pairs of compounds:
(a) Benzaldehyde and Benzoic acid
(b) Propanal and Propanone
Answer.

(c) Cl–CH₂–COOH 
(ii) (a) NaHCO₃ test.
(b) lodoform test./Fehling’s Test/Tollen’s Test

Question. (i) Describe the following reactions :
(a) Acetylation (b) Aldol condensation
(ii) Write the main product in the following equations :

Answer. (i) (a) The acyl groups are introduced at ortho- and para- positions by reaction of chlorobenzene with acyl halide in the presence of anhydrous aluminium chloride (a Lewis acid) as catalyst.

(b) Aldehydes and ketones having at least one a-hydrogen undergo a reaction in the presence of dilute alkali as catalyst to form b-hydroxy aldehydes (aldol) or b-hydroxy ketones (ketol), respectively.

Question. (i) Write the chemical reaction involved in Etard reaction.
(ii) Arrange the following in the increasing order of their reactivity towards nucleophilic addition reaction:
CH₃ – CHO, C₆H₅COCH₃, HCHO
(iii) Why pKa of Cl — CH₂ — COOH is lower than the pKa of CH₃COOH?
(iv) Write the product in the following reaction.

(v) A and B are two functional isomers of compound C₃H₆O. On heating with NaOH and l₂, isomer A forms yellow precipitate of iodoform whereas isomer B does not form any precipitate. Write the formulae of A and B.
Answer. (i) Etard reaction :

(ii) C₆H₅COCH₃ < CH₃CHO < HCHO
The reactivity of the compound towards nucleophilic addition reaction is directly proportional to electrophilic character of carbonyl carbon. In ketone, the +I group lowers the electrophilicity. Whereas, +I of methyl group in ethanal is less than that of –C₆H₅. Hence, ethanal is most reactive than acetophenone.
(iii) –Cl being electron withdrawing group stabilizes the ClCH₂COO– anion and increases the acidic strength.
Therefore, chloroacetic acid has lower pK_a value than acetic acid.

Question. (i) Draw the structures of the following derivatives :
(a) Propanone oxime,
(b) Semicarbazone of CH₃CHO.
(ii) How will you convert ethanal into the following compounds ? Give the chemical equations involved.
(a) CH₃—CH₃

(c) CH₃CH₂OH 
Answer.

Question. (i) Write structure of the product(s) formed :

(ii) How will you bring the following conversions in not more than two steps :
(a) Propanone to propene
(b) Benzyl chloride to phenyl ethanoic acid 
Answer. 

Question. (i) Give a simple chemical test to distinguish between the pair of organic compounds :
Ethanal and Propanal.
(ii) Name and complete the following chemical reaction :

(iii) Draw the structures of the following derivatives :
(a) The 2, 4-Dinitrophenylhydrazone of benzaldehyde,
(b) Acetaldehyde dimethyl acetal
(c) Cyclopropanone oxime. 
Answer. (i) Ethanal and propanal can be distinguished by Iodoform test.
Ethanal gives a yellow precipitate of iodoform with an alkaline solution of NaOH. Propanal does not gives this test.

The name of the reaction is Hell-Volhard-Zelinsky reaction.

Question. (a) Write the product(s) in the following reactions:

(b) Give simple chemical tests to distinguish between the following pairs of compounds :
(i) Butanal and Butan-2-one
(ii) Benzoic acid and Phenol
Answer.

(iii) CH₃ — CH = CH — CHO 
(b) (i) Tollen’s reagent test : Add ammoniacal solution of silver nitrate (Tollen’s reagent) in both the solutions. Butanal gives silver mirror whereas Butan-2-one does not. 
(ii) Add neutral FeCl₃ in both the solutions, phenol forms violet colour but benzoic acid does not.