Class 12 - Aldehydes, Ketones and Carboxylic Acids - 24577953

Aldehydes, Ketones and carboxylic acids
Ques 1:
i) Aldehydes other than formaldehyde react with Grignard’s reagent to give addition products
which on hydrolysis give
(a) tertiary alcohols
(b) secondary alcohols
(c) primary alcohols
(d) carboxylic acids
ii) Which of the following compounds will undergo Cannizzaro reaction?

(a) CH3CHO
(b) CH3COCH3
(c) C6H5CHO
(d) C6H5CH2CHO
iii) Propanal on treatment with dilute sodium hydroxide gives

(a) CH3CH2CH2CH2CH2CHO
(b) CH3CH2CH(OH)CH2CH2CHO
(c) CH3CH2CH(OH)CH(CH3)CHO
(d) CH3CH2COOH
iv) Alkene (X) (C5H10) on ozonolysis gives a mixture of two compounds (Y) and (Z).
Compound (Y) gives positive Fehling’s test and iodoform test. Compound (Z) does not give
Fehling’s test but give iodoform test. Compounds (X), (Y) and (Z) are
(a) C6H5COCH3 CH3CHO CH3COCH3
(b) CH3 CH =C(CH302 CH3CHO CH3COCH3
(c) CH3CH2CH == CH2 CH3CH2CHO HCHO
(d) CH3—CH == CH — CH3 CH3CHO CH3CHO
v) A compound (X) with a molecular formula C5H10O gives a positive 2,4-DNP test but a
negative Tollen’s test. On oxidation it gives a carboxylic acid (Y) with a molecular formula
C3H6O2. Potassium salt of (Y) undergoes Kolbe’s reaction and gives a hydrocarbon (Z). (X),
(Y) and (Z) respectively are
(a) pentan-3-one, propanoic acid, butane
(b) pentanal, pentanoic acid, octane
(c) 2-methylbutanone, butanoic acid, hexane
(d) 2, 2-dimethylpropanone, propanoic acid, hexane
vi) Which of the following will not give aldol condensation?

(a) Phenyl acetaldehyde
(b) 2-Methylpentanal
(c) Benzaldehyde
(d) 1-Phenylpropanone
vii) Which among the following is most reactive to give nucleophilic addition?
(a) FCH2CHO
(b) ClCH2CHO
(c) BrCH2CHO
(d) ICH2CHO
viii) The correct order of increasing acidic strength is
(a) Phenol < Ethanol < Chloroacetic acid < Acetic acid
(b) Ethanol < Phenol < Chloroacetic acid < Acetic acid
(c) Ethanol < Phenol < Acetic acid < Chloroacetic acid
(d) Chloroacetic acid < Acetic acid < Phenol < Ethanol
ix) To differentiate between pentan-2-one and pentan-3-one a test is carried out. Which of the
following is the correct answer?
(a) Pentan-2-one will give silver mirror test
(b) Pentan-2-one will give iodoform test.
(c) Pentan-3-one will give iodoform test
(d) None of these
x) Which of the following will not undergo HVZ reaction?

(a) Propanoic acid
(b) Ethanoic acid
(c) 2-Methylpropanic acid
(d) 2,2-Dimethylpropanoic acid
xi) Hydrocarbons are formed when aldehydes and ketones are reacted with amalgamated zinc
and conc. HCl. The reaction is called
(a) Cannizzaro reaction
(b) Clemmensen reduction
(c) Rosenmund reduction
(d) Wolff-Kishner reduction
xii) Propanone can be prepared from ethyne by

(a) passing a mixture of ethyne and steam over a catalyst, magnesium at 420°C
(b) passing a mixture of ethyne and ethanol over a catalyst zinc chromite
(c) boiling ethyne with water and H2SO4
(d) treating ethyne with iodine and NaOH.
xiii) What are the correct steps to convert acetaldehyde to acetone?

(a) CH3MgBr, H2O, Oxidation
(b) Oxidation, Ca(OH)2, Heat
(c) Reduction, KCN, Hydrolysis
(d) Oxidation, C2H5ONa, Heat
xiv) Arrange the following compounds in increasing order of their reactivity in nucleophilic
addition reactions. Ethanal, Propanal, Propanone, Butanone
(a) Butanone < Propanone < Propanal < Ethanal
(b) Propanone < Butanone < Ethanal > Propanal
(c) Propanal < Ethanal < Propanone < Butanone
(d) Ethanal < Propanal < Propanone < Butanone
xv) –OH group present in alcohols is neutral while it is acidic in carboxylic acid because
(a) in carboxylic acid –OH group is attached to electron withdrawing carbonyl group
(b) in alcohols –OH group is attached to alkyl group which is electron withdrawing
(c) carboxylic group is an electron releasing group
(d) alcoholic group is an electron withdrawing group.
Ques 2: (a) Assertion and reason both are correct statements and reason is correct explanation
for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for
assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement
i) Assertion : Aromatic aldehydes and formaldehyde undergo Cannizzaro reaction.

Reason : Aromatic aldehydes are almost as reactive as formaldehyde.
ii) Assertion : Acetic acid in vapour state shows a molecular mass of 120.
Reason : It undergoes intermolecular hydrogen bonding.
iii) Assertion : Boiling point of aldehydes lie in between parent alkanes and corresponding
alcohols. Reason : Aldehydes cannot form intermolecular hydrogen bonds like alcohols.
iv) Assertion : Benzaldehyde undergoes aldol condensation.

Reason : Aldehydes having a-hydrogen atom undergo aldol condensation
v) Assertion : o-Substituted benzoic acids are generally stronger acids than benzoic acids.
Reason : Increased strength is due to ortho-effect.
Ques 3: Read the passage given below and answer the following questions :
Carboxylic acids having an a-hydrogen atom when treated with chlorine or bromine in the
presence of small amount of red phosphorus gives a-halocarboxylic acids. The reaction is
known as Hell-Volhard-Zelinsky reaction
R—CH2—COOH + X2 -----red P----> R—CHX—COOH
When sodium salt of carboxylic acid is heated with soda lime it loses carbon dioxide and
gives hydrocarbon with less number of C-atoms.
R—COOH -----NaOH----> R—COONa
R—COONa -----NaOH + CaO/heat------> R—H + Na2CO3
i) Assertion : (CH3)3CCOOH does not give H.V.Z reaction.

Reason : (CH3)3CCOOH does not have a-hydrogen atom.
ii) Assertion : H.V.Z. reaction involves the treatment of carboxylic acids having a-hydrogens
with Cl2 or Br2 in presence of small amount of red phosphorus.
Reason : Phosphorus reacts with halogens to form phosphorus trihalides.
iii) Assertion : Propionic acid with Br2/P yields CH2Br—CHBr—COOH.

Reason : Propionic acid has two a-hydrogen atoms.
iv) Assertion : C6H5COCH2COOH undergoes decarboxylation easily than C6H5COCOOH.

Reason : C6H5COCH2COOH is a b-keto acid.
v) Assertion : On heating 3-methylbutanoic acid with soda lime, isobutane is obtained.

Reason : Soda lime is a mixture of NaOH + CaO in the ratio 3 : 1
Ques 4: Write chemical equations for the following reactions :
(i) Propanone is treated with dilute Ba(OH)2.
(ii) Acetophenone is treated with Zn(Hg)/Conc. HCl
Ques 5: Give reasons:

(i) Electrophilic substitution in benzoic acid takes place at meta-position.
(ii) Carboxylic acids do not give the characteristic reactions of carbonyl group.
Ques 6: A compound having the molecular formula C3H6O forms a crystalline white ppt.
with sodium bisulphite and reduces Fehling’s solution. Suggest the structural formula and
IUPAC name of this compound. Name an isomer for it from a group other than its own.
Ques 7: Account for the following:

(a) Aromatic carboxylic acids do not undergo Friedel–Crafts reaction.
(b) pKa value of 4-nitrobenzoic acid is lower than that of benzoic acid.
Ques 8: Account for the following:

(i) CH3CHO 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.
Ques 9: Two moles of organic compound ‘A’ on treatment with a strong base gives two
compound ‘B’ and ‘C’. Compound ‘B’ on dehydrogenation with Cu gives ‘A’ while
acidification of ‘C’ yields carboxylic acid ‘D’ with molecular formula of CH2O2. Identify the
compounds A, B, C and D and write all chemical reactions involved
Ques 10: a) How will you bring about the following conversions?
(i) Ethanal to but-2-enal
(ii) Propanone to propene
b) Draw the structures of the following :

(i) p-Methylbenzaldehyde
(ii) 4-Methylpent-3-en-2-one

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Aldehydes, Ketones and carboxylic acids

ii) Which of the following compounds will undergo Cannizzaro reaction?

iii) Propanal on treatment with dilute sodium hydroxide gives

vi) Which of the following will not give aldol condensation?

x) Which of the following will not undergo HVZ reaction?

xii) Propanone can be prepared from ethyne by

xiii) What are the correct steps to convert acetaldehyde to acetone?

i) Assertion : Aromatic aldehydes and formaldehyde undergo Cannizzaro reaction.

iv) Assertion : Benzaldehyde undergoes aldol condensation.

i) Assertion : (CH3)3CCOOH does not give H.V.Z reaction.

iii) Assertion : Propionic acid with Br2/P yields CH2Br—CHBr—COOH.

iv) Assertion : C6H5COCH2COOH undergoes decarboxylation easily than C6H5COCOOH.

v) Assertion : On heating 3-methylbutanoic acid with soda lime, isobutane is obtained.

Ques 5: Give reasons:

Ques 7: Account for the following:

Ques 8: Account for the following:

b) Draw the structures of the following :

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