Important Questions for CBSE Class 12 Chemistry – Aldehydes Ketones And Carboxylic Acids

  

Important Questions for CBSE Class 12 Chemistry – Aldehydes Ketones And Carboxylic Acids

Question 1:

Answer :

Question 2:
Name the reagents used in the following reactions:

Answer:

Question 3:
Write the reagents required in the following reactions:

Answer :

Question 4:
Name the reagents used in the following reactions:

Answer :

Question 5:
Write the reagents used iii the following reactions :

Answer :

Question 6:
Arrange the following compounds in increasing order of their property as indicated.

1. CH3CHO, C6H5CHO, HCHO (reactivity towards nucleophilic addition reaction).
2. 2,4-dinitrobenzoic acid, 4 methoxybenzoic acid, 4 nitrobenzoic acid(acidic character).

Answer :

1. C6H5CHO < CH3CHO < HCHO
2. 4-methoxybenzoic acid < 4-nitrobenzoic acid < 2, 4-dinitrobenzoic acid

Question 7:
Name the reagents used in the following reactions.

Answer:

Question 8:
Arrange the following compounds in increasing order of their property as indicated

Answer :

Short Answer Type Questions [II] [3 Marks]

Question 9:
Predict the products of the following reactions:

Answer :

Question 10:
Predict the products of the following reactions:

Answer :

Question 11:
Predict the products in the following reactions

Answer :

Question 12:
Predict the products in the following reactions:

Answer :

Long Answer Type Questions [5 Marks]

Question 13:
(a) Write the structures of A, B, C and D in the following reactions.

Answer :

Question 14:

Answer :

Question 15:

Answer :

Question 16:

Answer :

Question 17:

Answer :

Question 18:

Answer :

2014

Very Short Answer Type Questions [1 Marks]

Question 19:
Write the IUPAC name of compound.

Answer :
3-hydroxy butanoic acid.

Question 20:
Write the IUPAC name of compound.

Answer :
4-hydroxy-2-pentanone.

Question 21:
Write the IUPAC name of compound.

Answer :
4-hydroxy-2-pentanone.

Question 22:
Write the structure of p-methylbenzaldehyde.

Answer :

Question 23:
Write the structure of 4-chloropentan-2-one.
Answer :

Question 24:
Write the structure of 2-hydroxybenzoic acid.
Answer :

Question 25:
Write the IUPAC name of the following compound:

Answer :
2-methyl propanal

Question 26:
Write the IUPAC name of the following

Answer :
2-hydroxy benzaldehyde.

Long Answer Type Questions [5 Marks]

Question 27:
Write the products of the following reactions :

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

Answer :

(b)(i) Add NaHC03 solution to 2 mL of each in a test tube. Benzaldehyde will not react, whereas benzoic acid will give brisk effervescence due to C02.
(ii) Add I2 and NaOH. Propanal will not give yellow ppt, whereas propanone will give yellow ppt, due to iodoform.

Question 28:
(a)Account for the following:
(i) CH3CHO is more reactive than CH3COCH3 towards reaction with HCN.
(ii) Carboxylic acid is a stronger acid than phenol.
(b)Write the chemical equations to illustrate the following name reactions:
(i) Wolff-Kishner reduction
(ii) Aldol condensation
(iii) Cannizzaro reaction
Answer :
(i) CH3CHO is more polar and has less stearic hindrance, therefore, more reactive with HCN than CH3COCH3.
(ii) Carboxylate ions are more stable than phenoxide ions as negative charge is delocalised on two oxygen atoms in carboxylate ions.

Question 29:

Answer :

Question 30:
(a) Account for the following:
(i) Cl—CH2COOH is a stronger acid than CH3COOH.
(it) Carboxylic acids do not give reactions of carbonyl group.
(b) Write the chemical equations to illustrate the following name reactions:
(i) Rosenmund reduction (ii) Cannizzaro’s reaction
(c) Out of CH3CH2—CO—CH2—CH3 and CH3CH2—CH2—CO—CH3, which gives iodoform test?
Answer :

Question 31:
(a) Write the products formed when ethanal reacts with the following reagents:
(i) CH3MgBr and then H30+
(ii) Zn-Hg/conc. HCl
(iii) C6H5CHO in the presence of dilute NaOH

(b) Give simple chemical tests to distinguish between the following pairs of compounds:
(i) Benzoic acid and Ethyl benzoate
(ii) Propanal and Butan-2-one

Question 32:
(a) Account for the following:
(i) CHsCHO is more reactive than CH3COCH3 towards reaction with HCN.
(ii) There are two -NH2 groups in semicarbazide (H2NNHCONH2).
However, only one is involved in the formation of semicarbazone.

(b)Write the chemical equations to illustrate each of the following name reactions:
(i)Rosenmund reduction
(ii) Cannizzaro reaction
(iii) Hell-Volhard-Zelinsky reaction
Answer :

Question 33:
(a)Describe:
(i) Aldol condensation     (ii) Cannizzaro’s reaction

(b)Describe the chemical test to distinguish between.
(i) Ethanol and Propanol
(ii) Benzaldehyde and Acetophenone
(iii) Pentan-2-one and Pentan-3-one

Answer :

Question 34:
(a)Draw the structures of the following compound:
(i) 4-chloro pentan-2-one    (ii) But-2-en-l-al

Answer :

Question 35:
Write the IUPAC name of the compound

(b)How will you carry out following conversions:
(i) Ethanol to 3-hydroxy butanal.
(ii) Benzoic acid to m-nitrobenzylalcohol.
(iii) Acetone to Propene.
Answer :
(i) Heptan-2-one
(ii) 3-Phenyl prop-2-en-l-al

2013

Very Short Answer Type Questions [1 Mark]

Question 36:
Write the structure of 3-methylbutanal.
Answer :

Question 37:
Write the structure of 4-chloropentan-2-one.
Answer :

Question 38:
Write the structure of jb-Methylbenzaldehyde molecule.
Answer :

Question 39:
Ethanal is soluble in water. Why?
Answer :
It is because it can form H-bonds with water.

Question 40:
Write the structure of 3-hydroxybutanal.
Answer :

Question 41:
Write the structural formula of 2-phenylethanoic acid.
Answer :

Question 42:
Write the structure of 4-methylpent-3-en-2-one.
Answer :

Long Answer Type Questions [5 Marks]

Question 43:
Although phenoxide ion has more number of resonating structures than Carboxylate ion, Carboxylic acid is a stronger acid than phenol. Give two reasons.
How will you bring about the following conversions?
(i) Propanone to propane
(ii) Benzoyl chloride to benzaldehyde
(iii) Ethanal to but-2-enal
Answer :
(a)In carboxylate ions, negative charge is delocalised over two oxygen atoms which is more stable.
Phenoxide is less stable as negative charge is delocalised over one oxygen atom and carbon atoms of benzene ring.

Question 44:

Answer :

Question 45:
(a) How will you convert the following:
(i) Propanone to Propan-2-ol (iti Ethanal to 2-Hydroxypropanoic acid (iii) Toluene to Benzoic acid

(b) Give simple chemical test to distinguish between:
(i) Pentan-2-one and Pentan-3-one (ii) Ethanal and Propanal
Answer :

Question 46:

Answer :

Question 47:
(a) Give reasons for the following:
(i) Ethanal is more reactive than acetone towards nucleophilic addition reaction.
(ii) (CH3)3C—CHO does not undergo aldol condensation.
(iii) Carboxylic acids are higher boiling liquids than alcohols.
(b) Give a simple chemical test to distinguish between:
(i) Acetophenone and Benzophenone
(ii) Benzaldehyde and Ethanal
Answer :
(a) (i) It is because ethanal is more polar than acetone due to only one methyl group, whereas in acetone, there are two methyl groups which are electron releasing and reduce positive charge on carbonyl carbon.
(ii) It is because (CH3)3C—CHO does not have alpha (a) hydrogen.
(iii) It is due to greater intermolecular H-bonding in carboxylic acids than alcohols and they exist as dimers.
(b) (i) Add I2 and NaOH. Acetophenone will give yellow ppt. of iodoform, whereas Benzophenone will not react.
(ii) Add I2 and NaOH. Ethanal will give yellow ppt. of iodoform, whereas benzaldehyde will not react.

Question 48:

Answer :

2012-Very Short Answer Type Questions [1 Mark]

Question 49:

Answer :

Question 50:
Write the IUPAC name of

Answer :

Question 51:
Draw the molecular structure of 4-hydroxy-4-methylpentan-2-one
Answer :

Question 52:
Arrange the following compounds in an increasing order of their reactivity in nucleophilic addition reactions:
ethanal, propanal, propanone, butanone.
Answer :
butanone < propanone < propanal < ethanal.

Question 53:
Write the IUPAC name of Ph—CH=CH—CHO
Answer :
3-Phenyl prop-2-en-l-al.

Question 54:
Draw the molecular structure of the compound 4-methylpent-3-en-2-one.
Answer :

Short Answer Type Question [I] [2 Marks]

Question 55:
Give chemical tests to distinguish between the following pairs of compounds:
(i)Propanoyl chloride and Propanoic acid
(ii) Benzaldehyde and Acetophenone
Answer :
(i) Add NaHC03 solution to each of them. Propanoyl chloride will not react, whereas propanoic acid will give brisk effervescence due to C02.
(ii)Refer Ans. to Q.33 (b) (ii).

Long Answer Type Questions [5 Marks]

Question 56:
(a)Illustrate the following name reactions giving suitable example in each case
(i) Clemmensen reduction
(ii) Hell-volhard-zelinsky reaction

(b)How are the following convensions carried out?
(i) Ethylcyanide to ethanoic acid
(ii) Butan-l-ol to butanoic acid
(iii)Benzoic acid to m-bromobenzoic acid
Answer :

Question 57:
Answer :

Question 58:
(a) Give chemical test to distinguish between
(i) Phenol and Benzoic acid
(ii) Benzophenone and Acetophenone

(b) Write the structures of the main products of following reactions:

Answer :
(a) (i) Refer Ans. to Q.44 (b) (ii).
(ii) Refer Ans. to Q.47 (b) (i).

Question 59:
(a) Give a plausible explanation for each one of the following:
(i) There are two-NH2 groups in semicarbazide. However, only one such group is involved in the formation of semicarbazones.
(ii) Cyclohexanone forms cyanohydrin in good yield but 2, 4, 6-tri- methylcyclohexanone does not.
(b) An organic compound with molecular formula CgH10O forms 2, 4-DNP derivative, reduces Tollens’ reagent and undergoes Cannizzaro’s reaction. On vigrous oxidation it gives 1, 2-benzene-dicarboxylic acid. Identify the compound.
Answer :

Question 60:
(a) Write a suitable chemical equation to complete each of the following transformations.
(i) Butan-l-al to butanoic acid
(ii) 4 -Methylacetophenone to benzene-1, 4-dicarboxylic acid.
(b) An organic compound with molecular formula CgHI0O forms 2, 4-DNP derivative, reduces Tbllens’ reagent and undergoes Cannizzaro’s reaction. On vigrous oxidation it gives 1, 2-benzene-dicarboxylic acid. Identify the compound.
Answer :

Question 61:
(a) Give chemical tests to distinguish between:
(i) propanal and propanone
(ii) benzaldhyde and acetophenone

(b) Arrange the following compounds in an increasing order of their property as indicated.
(i) Acetaldehyde, acetone, methyl tert-butyl ketone (reactivity toward HCN).
(ii) Benzoic acid, 3,4-Dinitrobenzoic acid, 4-methoxybenzoic acid (acid strength)
(iii) CH3CH2CH(Br)COOH, CH3CH(Br)CH2COOH, (CH3)2CHCOOH (acid strength)

Answer :

Question 62:
(a) Describe the mechanism of the addition of Grignard reagent to the carbonyl group of compound to form an adduct which on hydrolysis yields an alcohol.

(b) Draw the structure of die following compounds
(i) 3-Methylbutanal
(ii) Hexane-1, 6-dioic acid
(iii) P-Nitropropiophenone
Answer :

Question 63:
(a) Illustrate the following reactions giving a suitable chemical equation for each:
(i) Cannizzaro reaction
(ii) Hell-Volhard-Zelinsky reaction

(b) How would you bring about the flowing conversions? Write the complete equation in each case
(i) Ethanal to 3-hydroxybutanal
(ii) Benzoic acid to m-nitrobenzyl alcohol
(iii) Benzaldehyde to benzophenone

Answer :
(a) (i) Refer Ans. to Q.28 (b) (ii).
(ii) Refer Ans. to Q.32 (b) (ii).

(b) (i) Refer Ans. to Q.35 (b) (i).

2011

Very Short Answer Type Questions [1 Mark]

Question 64:
Draw the structure of 3-methylbutanal.
Answer :

Question 65:
Draw the structure of 4-chloropentan-2-one.
Answer :

Question 66:
Write the structure of the following compound: 3-oxopentanal
Answer :

Question 67:
(a) Illustrate the following name reactions:
(i) Cannizzaro’s reaction
(ii) Clemmensen reduction

(b) How would you obtain the following:
(i) But-2-enal from ethanal,
(ii) Butanoic acid from butanol,
(iii) Benzoic acid from ethylbenzene?

Answer :
(a) (i) Refer Ans. to Q.33 (a) (ii).
(ii) Refer Ans. to Q.56 (a) (i).

Question 68:
(a) Give chemical tests to distinguish between the following:
(i) Benzoic acid and ethylbenzoate (ii) Benzaldehyde and acetophenone
(b) Complete each synthesis by giving missing reagents or products in the

Answer :

Question 69:
(a) Give chemical tests to distinguish between
(i) Propanal and propanone (ii) Benzaldhyde and acetophenone.
(b) How would you obtain the following:
(i) But-2-enal from ethanal,
(ii) Butanoic acid from butanol,
(iii) Benzoic acid from ethylbenzene?
Answer :
(a) (i) Refer Ans. to Q.27 (b) (ii).
(ii) Refer Ans. to Q.33 (b) (ii).
(b) (i) Refer Ans. to Q.67 (b) (i).
(ii) Refer Ans. to Q.67 (b) (ii).
(Hi) Refer Ans. to Q.67 (b) (Hi).

Question 70:
(a) Describe the following giving linked chemical equations
(i) Cannizzaro reaction
(ii) Decraboxylation

Answer :

2010

Very Short Answer Type Questions [1 Mark]

Question 71:
Draw the structural formula of 1 -phenylpropan-1 -one molecule.

Answer :

Question 72:
What is Tollens’ reagent? Write one usefulness of this reagent.

Answer :

It is ammonical silver nitrate (AgNOs + NH4OH) solution. It is used as mild oxidising agent to test the presence of aldehyde group.

Question 73:
Write the IUPAC name of the compound

Answer :
4-hydroxy-4-methyl pentan-2-one.

Question 74:
Write the IUPAC name of the following compound:

Answer :
2-Chlorophenyl ethanone

Question 75:
Give the IUPAC name of the following compound

Answer :

Question 76:
(a) Explain the mechanism of a nucleophilic attack on the carbonyl group of an aldehyde or a ketone.

(b) An organic compound (A) (molecular formula C8H1602) was hydrolysed with dilute sulphuric acid to give a carboxylic acid (B) and an alcohol (C). Oxidation of (C) with chromic acid also produced (B). On dehydration (C) gives but-l-ene. Write the equations for the reactions involved.

Answer :

Question 77:
(a) How will you prepare the following compounds starting with benzene:
(i) Benzaldehyde
(ii) Acetophenone

(b) Give chemical tests to distinguish between the following pairs of com­pounds
(i) Ethanal and Propanal
(ii) Benzaldehyde and Acetophenone
Answer :

(b) (i) Refer Ans. to Q.44 (b) (i).
(ii) Refer Ans. to Q.33 (b) (ii).
(iii) Refer Ans. to Q.44 {b) (ii).

Question 78:

(a) Explain the mechanism of nucleophilic attack on a carbonyl group of an aldehyde or a ketone.

(b) How would you bring about the following conversions:
(i) Propanone to Propene
(ii) Ethanol to 3-hydroxybutanal
(iii) Benzaldehyde to Benzophenone
Answer :

Question 79:
(a) Give chemical tests to distinguish between the following pairs of compounds
(i) Ethanal and Propanal
(ii) Phenol and Benzoic acid

(b) How will you bring about the following conversions:
(i) Benzoic acid to benzaldehyde
(ii) Ethanal to but-2-enal
(iii) Propanone to propene
Give complete reaction in each case.

Answer :
(a) (i) Refer Ans. to Q.44 (b) (i).

Question 80:
(a) Illustrate the following name reaction* giving a chemical equation in each case
(i) Clemmensen reaction
(ii) Cannizzaro’s reaction

(b) Describe how the following conversions can be brought about
(i) Cyciohexanol to cyclohexan-l-one
(ii) Ethyl benzene to benzoic 3cid
(iii) Bromobenzene to benzoic acid

Answer :
(a) (i) Refer Ans. to Q.56 (a) (i).
(ii) Refer Ans. to Q.30 (b) (ii).

Question 81:
(a) Illustrate the following name reactions
(i) Hell-Volhard-Zelinsky reaction
(ii) Wolff-Kishner reduction reaction

(b) How are the following conversions carried out
(i) Ethylcyanide to ethanoic acid
(ii) Butan-l-ol to butanoic acid
(iii) Methylbenzene to benzoic acid

Answer :
(a)(i) Refer Ans. to Q.32 (b) (ii).
(ii) Refer Ans. to Q.28 (b) (i).
(b)(i) Refer Ans. to Q.56 (b) (i).
(ii) Refer Ans. to Q.56 (b) (ii).

2009

Very Short Answer Type Questions [1 Mark]

Question 82:
Write the structural formula of 1-phenylpentan-l-one.

Answer :

Question 83:
Write the structure of pent-2-enal.

Answer :

Question 84:
Write the IUPAC name of the following

Answer :
4-hydroxy-4-methyl-pentan-2-one.

Question 85:
Write the IUPAC name of the following:

Answer :
2,4-Dimethyl pentan-3-one.

Question 86:
Write the IUPAC name of the following:

Answer :
1-Phenyl propanone.

Question 87:
Write the structure of 3-oxopentanal.
Answer :

Long Answer Type Questions [5 Marks]

Question 88:
(a) How are the following obtained?
(i) Benzoic acid from ethylbenzene.
(ii) Benzaldehyde from toluene.
(b) Complete each synthesis by giving the missing material, reagent or products:

Answer :

Question 89:
(a) Write chemical equations to illustrate the following name bearing reactions:
(i) Cannizzaro’s reaction (ii) Hell-Volhard-Zelinsky reaction
(b) Give chemical tests to distinguish between the following pairs of compounds:
(i) Propanal and Propanone (ii) Acetophenone and Benzophenone
(iii) Phenol and Benzoic acid

Answer :
(a) (i) Refer Ans. to Q.30 (b) (ii).
(ii) Refer Ans. to Q.32 (b) (ii).
(b) (i) Refer Ans. to Q.27 (b) (ii).
(ii) Refer Ans. to Q.47 (b) (i).
(iii) Refer Ans. to Q.44 (b) (ii).

Question 90:
(а) Illustrate the following name reactions by giving example:
(i) Cannizzaro’s reaction
(ii) Clemmensen reduction

(b)An organic compound contains 69.77% carbon, 11.63% hydrogen and the rest is oxygen. The molecular mass of the compound is 86. It does not reduce Tollens’ reagent but forms an addition compound with sodium hydrogen sulphite and gives a positive iodoform test. On vigorous oxidation it gives ethanoic and propanoic acids. Deduce the possible structure of the organic compound.

Answer :
(a) (i) Refer Ans. to Q.30 (b) (ii).
(ii) Refer Ans. to Q.56 (a) (i).

Question 91:
An organic compound (A) on treatment with acetic acid in the presence of sulphuric acid produces an ester (B). (A) on mild oxidation gives (C). (C) with 50% KOH followed by acidification with dilute HC1 generates (A) and (D). (D) with PC15 followed by reaction with ammonia gives (E). (E) on dehydration produces hydrocyanic acid. Identify the compounds A, B, C, D and E.
Answer :

Question 92:

(a) Arrange the following compounds in an increasing order of their indicated property:
(i) Benzoic acid, 4-Nitrobenzoic acid, 3, 4-Dinitrobenzoic acid, 4-Methoxybenzoic acid (acid strength).
(ii) CH3CH2CH(Br)COOH, CH3CH(Br)CH2COOH, (CH3)2CHCOOH, CH3CH2CH2COOH (acid strength).
(b) How would you bring about the following conversions (I) Propanone to propene (iI) Benzoic acid to Benzaldehyde
(iii) Bromobenzene to 1-phenylethanol.
Answer :

Question 93:
(a) How will you bring about the following conversions:
(i) Ethanol to 3-hydroxybutanal (ii) Benzaldehyde to benzophenone

(b) An organic compound A has the molecular formula C8H1602. It gets
hydrolysed with dilute sulphuric acid and gives a carboxylic acid B and an alcohol C. Oxidation of C with chromic acid also produced B. C on dehydration reaction gives but-l-ene. Write equations for the reactions involved.

Answer :
(a) (i) Refer Ans. to Q.35 (b) (i).
(ii) Refer Ans. to Q.63 (b) (iii).
(b) Refer Ans. to Q.76 (b).