Chapter-12 Aldehydes, Ketones and Carboxylic Acids

When liquid ‘A’ is treated with a freshly prepared ammoniacal silver nitrate
solution, it gives bright silver mirror. The liquid forms a white crystalline solid
on treatment with sodium hydrogensulphite. Liquid ‘B’ also forms a white
crystalline solid with sodium hydrogensulphite but it does not give test with
ammoniacal silver nitrate. Which of the two liquids is aldehyde? Write the
chemical equations of these reactions also.

Write down functional isomers of a carbonyl compound with molecular
formula C3H6O. Which isomer will react faster with HCN and why? Explain
the mechanism of the reaction also. Will the reaction lead to the completion
with the conversion of whole reactant into product at reaction conditions? If a
strong acid is added to the reaction mixture what will be the effect on
concentration of the product and why?

An aromatic compound ‘A’ (Molecular formula C8H8O) gives positive
2, 4-DNP test. It gives a yellow precipitate of compound ‘B’ on treatment with
iodine and sodium hydroxide solution. Compound ‘A’ does not give Tollen’s
or Fehling’s test. On drastic oxidation with potassium permanganate it forms
a carboxylic acid ‘C’ (Molecular formula C7H6O2), which is also formed along
with the yellow compound in th

An alkene ‘A’ (Mol. formula C5H10) on ozonolysis gives a mixture of two
compounds ‘B’ and ‘C’. Compound ‘B’ gives positive Fehling’s test and also
forms iodoform on treatment with I2 and NaOH. Compound ‘C’ does not give
Fehling’s test but forms iodoform. Identify the compounds A, B and C. Write
the reaction for ozonolysis and formation of iodoform from B and C.

Match the acids given in Column I with their correct IUPAC names given in
Column II.
Column I Column II
(Acids) (IUPAC names)
(i) Phthalic acid (a) Hexane-1,6-dioic acid
(ii) Oxalic acid (b) Benzene-1,2-dicarboxylic acid
(iii) Succinic acid (c) Pentane-1,5-dioic acid
(iv) Adipic acid (d) Butane-1,4-dioic acid
(v) Glutaric acid (e) Ethane-1,2-dioic acid

Match the common names given in Column I with the IUPAC names given in
Column II.
Column I Column II
(Common names) (IUPAC names)
(i) Cinnamaldehyde (a) Pentanal
(ii) Acetophenone (b) Prop-2-enal
(iii) Valeraldehyde (c) 4-Methylpent-3-en-2-one
(iv) Acrolein (d) 3-Phenylprop-2-enal
(v) Mesityl oxide (e) 1-Phenylethanone

Can Gatterman-Koch reaction be considered similar to Friedel Craft’s acylation?
Discuss.

Ethylbenzene is generally prepared by acetylation of benzene followed by
reduction and not by direct alkylation. Think of a possible reason.

Why are carboxylic acids more acidic than alcohols or phenols although all of
them have hydrogen atom attached to a oxygen atom (—O—H)?

Carboxylic acids contain carbonyl group but do not show the nucleophilic
addition reaction like aldehydes or ketones. Why?

Compound ‘A’ was prepared by oxidation of compound ‘B’ with alkaline KMnO4.
Compound ‘A’ on reduction with lithium aluminium hydride gets converted
back to compound ‘B’. When compound ‘A’ is heated with compound B in the
presence of H2SO4 it produces fruity smell of compound C to which family the
compounds ‘A’, ‘B’ and ‘C’ belong to?

Compound ‘A’ was prepared by oxidation of compound ‘B’ with alkaline KMnO4.
Compound ‘A’ on reduction with lithium aluminium hydride gets converted
back to compound ‘B’. When compound ‘A’ is heated with compound B in the
presence of H2SO4 it produces fruity smell of compound C to which family the
compounds ‘A’, ‘B’ and ‘C’ belong to?

Compound ‘A’ was prepared by oxidation of compound ‘B’ with alkaline KMnO4.
Compound ‘A’ on reduction with lithium aluminium hydride gets converted
back to compound ‘B’. When compound ‘A’ is heated with compound B in the
presence of H2SO4 it produces fruity smell of compound C to which family the
compounds ‘A’, ‘B’ and ‘C’ belong to?
30. Arrange the following in decreasing order

What product will be formed on reaction of propanal with 2-methylpropanal in
the presence of NaOH? What products will be formed? Write the name of the
reaction also.

Oxidation of ketones involves carbon-carbon bond cleavage. Name the products
formed on oxidation of 2, 5-dimethylhexan-3-one.

Name the electrophile produced in the reaction of benzene with benzoyl chloride
in the presence of anhydrous AlCl3. Name the reaction also.

Benzaldehyde can be obtained from benzal chloride. Write reactions for
obtaining benzalchloride and then benzaldehyde from it.

Give the structure of the following compounds.
(i) 4-Nitropropiophenone
(ii) 2-Hydroxycyclopentanecarbaldehyde
(iii) Phenyl acetaldehyde

Write a test to differentiate between pentan-2-one and pentan-3-one.

Why is there a large difference in the boiling points of butanal and butan-1-ol?

Although phenoxide ion has more no. of resonating structures than carboxylate ion , even though carboxylic acid is a stronger acid why ?

Why Corboxylic acid have higher boiling point than alcohols as alcohol forms strongest inter molecular hydrogen bonding?

There are two-NH2 group in semicarbazide . However only one is involved in formation of semicarbazones. Why?

Why does solubility decreases with increasing molecular mass in carboxytic acid?

Why are aldehydes are more reactive than ketones when undergo nucleophillic addition reaction?

Why PCC cannot oxidise methanol to methanoic acid and while

KMNO4 can?

During preparation of esters from a carboxylic acid and an alcohol in the presence of acid catalyst water or ester formed should be removed as soon as it is formed.

Suggest a reason for the large difference in the boling point of butanol and butanal although they have same solubility in water.

Would you expect benzaldehyde to be more reactive or less reactive in nuderophillic addition reaction than propanol. Explain.

   Why does methanal not give aldol condensation while ethanol gives?

Why does methanal undergo cannizaro’s reaction?

Explain why O-hydroxy benzaldehyde is a liquid at room temperature while p- hydroxy benzaldehyde is a high melting solid.

Why is the boiling point of an acid anhydride higher than the acid from which it is derived?

Why do Carboxylic acids not give the characteristic reactions of a carbonyl group?

Cyclohexanone forms cyanohydrin in good yield but 2,2,6 trimethyle cyclo-hexanone does not. Why?

Why is carboxyl group in benzoic acid meta directing?

Treatment of Benzaldehyde with HCN gives a mixture of two isomers which cannot be separated even by careful fractional distillation. Explain why?

Sodium Bisulphite is used for the purification of aldehydes and

Ketones. Explain.

Why pH of reaction should be carefully controlled while preparing ammonia derivatives of carbonyl compound?

Why formic acid is stronger acid than acetic acid?

Why is oxidation of alcohals to get aldehydes carried out under controlled conditions?

Why the oxidation of toluene to benzaldehyde with CrO3 is carried out in the presence of acetic anhydride.

Melting point of an acid with even no. of carbon atoms is higher than those of its neighbour with odd no. of carbon atoms.

    Why do aldehydes have lower boiling point than corresponding alcohals?

Why do aldehydes behave like polar compounds?

Most aromatic acids are solids while acetic acid and others of this series are liquids. Explain why?

ethers possess a dipole moment ever if the alkyl radicals in the molecule are identical. Why?

Why does acyl chorides have lower boling point than corresponding acids?

Why ethers are stored in coloured bottles?

  Why formaldehyde cannot be prepared by Rosenmund’s reduction?

Two moles of organic compound A on treatment with a strong base gives two compounds B and C. Compound B on dehydration with cu gives A while  acidification of C yields carboxylic acid D having molecular formula of CH2O2 .Identify the compoundsA,B,C,D

An aliphatic compound    A’with a molecular formula of C3H6O reacts with phenylhydrazine to give compound   B’ . Reaction  of   A’ with I2 in alkalene medium on warming gives a yellow precipitate   C’. Identify the component A,B,C

An organic compound   A’ has the molecular formula C5H10O .It

does not reduse fehling’s solution but forms a bisulphite compound

.It also gives positive Iodoform test. What are possible structure of

 A’ ?Explain your reasoning.

An organic compound   A’ which has characterstic odour , on treatment with NaOH forms two compounds   B’ and   C’.

Compound   B’ has the molecular formula C7H8O which on oxidation

gives back compound   A’. Compound ‘C’ is the sodium salt of an acid which when heated with soda lime yields an aromatic hydrocarbon   D’. Deduce  A,B,C,D

An organic compound   A’ is resistant to oxidation forms an oxidation forms a compound 'B  (C3H80) on reduction .  B'reacts with  HBr to form a bromide   C’ which on treatment with alkoholic

KOH forms an alkene   D’ (C3H6). Deduce A,B,C,D.

Primary alkyl halide C4H9Br (A) reacted with alcoholic KOH to give compound (B) is reacted with HBr to give (C) which is an isomer of (A). When (A) is reacted with sodium metal it gives compound (D) C8H18 that was different from the compound formed when n‐butyl bromide is reacted with sodium . Give the formula of (A) and write equations.

 An aromatic compound A on treatment with aqueous ammonia and heating forms compound B which on heating with Br2 and KOH forms a compound  C of molecular formula C6H7N  .Identify A,B,C .

An organic compound   A’ having molecular formula C2H5O2N reacts with HNO2 and gives C2H4O3N2. On reduction   A’ gives a compound ‘B’ with molecular formula C2H7N.  C’ on treatment with HNO2 gives   C’ which givespositive idoform test . Identify A,B,C.

Idomethane reacts with KCN to form a major product A .Compound   A’ on reduction in presence of LiAlH4 forms a higher amine 'B’. Compound B on treatment with CuCl2 forms a blue colur complex C . Identify A,B,C

An aliphatic compound A with molecular formula C2H3Cl on treatment with AgCN gives two isomeric compounds of unequal amount with the molecular formula C3H3N .The minor of these two products on complete reduction with H2  in the presence of Ni gives a compound ‘B’ with molecular formula C3H9N.Identify the

compounds.

A compound ‘X’ having molecular formula C3H7NO reacts with Br2 in presence of KOH to give another compound Y. the compound Y reacts with HNO2 to form ethanol N2 gas. Identify X,Y,

A compound   A’ of molecular formula C3H7O2N reaction with Fe and conc, HCl gives a compound   B’ OF molecular formula C3H9N. Compound   B’ on treatment with NaNO2  and HCl gives another compound   C’ of molecular formula C3H8o.The compound

 C’gives effervescences with Na on oxidation with CrO3.The

compound   C’ gives a saturated aldehyde containing three carbon atom deduce A,B,C.

A Chloro compound   A’ on reduction with Zn – Cu and alcohol gives the hydro carbon (B) with five carbon atom.When   A’ is dissolved in ether and treated with sodium 2,2,5,5 tetramethyl hexhane is formed structure of A and B?

Name the reaction and the reagent used for the conversion of acid chlorides to the corresponding aldehydes.

Suggest a reason for the large difference in the boiling points of butanol and butanal, although they have same solubility in water

What type of aldehydes undergo Cannizaro reaction ?

Out of acetophenone and benzophenone, which gives iodoform test ? Write the reaction involved. (The compound should have CH3CO-group to show the iodoform test.)

Give Fehling solution test for identification of aldehyde gp (only equations). Name thealdehyde which does not give Fehling‘s soln. test. 

What makes acetic acid a stronger acid than phenol ?

Why HCOOH does not give HVZ (Hell Volhard Zelinsky) reaction but

CH3COOH does?

During preparation of esters from a carboxylic acid and an alcohol in

the presence of an acid catalyst, water or the ester formed should be removed as soon as it is formed.

Arrange the following compounds in increasing order of their acid strength. Benzoic acid, 4‐Nitrobenzoic acid, 3, 4‐dinitrobenzoic acid, 4‐methoxy benzoic acid.

How is tert‐butyl alcohol obtained from acetone? A.

Explain why o‐hydroxybenzaldehyde is a liquid at room temperature while p‐hydroxybenzaldehyde is a high melting solid.

Although phenoxide ion has more number of resonating structures than carboxylate ion, carboxylic acid is a stronger acid than phenol. Why?

An organic compound contains 69.77% carbon, 11.63% hydrogen and rest oxygen. The molecular mass of the compound is 86. It does not reduce Tollens' reagent but forms an addition compound with sodium hydrogensulphite and give positive iodoform test. On vigorous oxidation it gives ethanoic and propanoic acid. Write the possible structure of the compound.

Give plausible explanation for each of the following:

(i) Cyclohexanone forms cyanohydrin in good yield but 2, 2, 6 trimethylcyclohexanone does not.

(ii) There are two -NH₂ groups in semicarbazide. However, only one is involved in the formation of semicarbazones.

(iii) During the preparation of esters from a carboxylic acid and an alcohol in the presence of an acid catalyst, the water or the ester should be removed as soon as it is formed.

Complete each synthesis by giving missing starting material, reagent or products

(i)

(ii)

(iii)

(iv)

(v)

(vi)

(vii)

(viii)

(ix)

(x)

(xi)

Describe the following:

(i) Acetylation

(ii) Cannizzaro reaction

(iii) Cross aldol condensation

(iv) Decarboxylation

How will you prepare the following compounds from benzene? You may use any inorganic reagent and any organic reagent having not more than one carbon atom

(i) Methyl benzoate (ii) m-Nitrobenzoic acid

(iii) p-Nitrobenzoic acid (iv) Phenylacetic acid

(v) p-Nitrobenzaldehyde.

Give simple chemical tests to distinguish between the following pairs of compounds.

(i) Propanal and Propanone

(ii) Acetophenone and Benzophenone

(iii) Phenol and Benzoic acid

(iv) Benzoic acid and Ethyl benzoate

(v) Pentan-2-one and Pentan-3-one

(vi) Benzaldehyde and Acetophenone

(vii) Ethanal and Propanal

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

(i) Acetaldehyde, Acetone, Di-tert-butyl ketone, Methyl tert-butyl ketone (reactivity towards HCN)

(ii) CH₃CH₂CH(Br)COOH, CH₃CH(Br)CH₂COOH, (CH₃)₂CHCOOH, CH₃CH₂CH₂COOH (acid strength)

(iii) Benzoic acid, 4-Nitrobenzoic acid, 3,4-Dinitrobenzoic acid, 4-Methoxybenzoic acid (acid strength)

An organic compound (A) (molecular formula C₈H₁₆O₂) was hydrolysed with dilute sulphuric acid to give a carboxylic acid (B) and an alcohol (C). Oxidation of (C) with chromic acid produced (B). (C) on dehydration gives but-1-ene.Write equations for the reactions involved.

An organic compound with the molecular formula C₉H₁₀O forms 2, 4-DNP derivative, reduces Tollens' reagent and undergoes Cannizzaro reaction. On vigorous oxidation, it gives 1, 2-benzenedicarboxylic acid. Identify the compound.

Write structural formulas and names of four possible aldol condensation products from propanal and butanal. In each case, indicate which aldehyde acts as nucleophile and which as electrophile.

How will you convert ethanal into the following compounds?

(i) Butane-1, 3-diol (ii) But-2-enal (iii) But-2-enoic acid

Which of the following compounds would undergo aldol condensation, which the Cannizzaro reaction and which neither? Write the structures of the expected products of aldol condensation and Cannizzaro reaction.

(i) Methanal (ii) 2-Methylpentanal

(iii) Benzaldehyde (iv) Benzophenone

(v) Cyclohexanone (vi) 1-Phenylpropanone

(vii) Phenylacetaldehyde (viii) Butan-1-ol

(ix) 2, 2-Dimethylbutanal

Predict the products formed when cyclohexanecarbaldehyde reacts with following reagents.

(i) PhMgBr and then H₃O⁺

(ii)Tollens' reagent

(iii) Semicarbazide and weak acid

(iv)Excess ethanol and acid

(v) Zinc amalgam and dilute hydrochloric acid

Draw structures of the following derivatives.

(i) The 2,4-dinitrophenylhydrazone of benzaldehyde

(ii) Cyclopropanone oxime

(iii) Acetaldehydedimethylacetal

(iv) The semicarbazone of cyclobutanone

(v) The ethylene ketal of hexan-3-one

(vi) The methyl hemiacetal of formaldehyde

Write the IUPAC names of the following ketones and aldehydes. Wherever possible, give also common names.

(i) CH₃CO(CH₂)₄CH₃ (ii) CH₃CH₂CHBrCH₂CH(CH₃)CHO

(iii) CH₃(CH₂)₅CHO (iv) Ph-CH=CH-CHO

(v)  (vi) PhCOPh

Draw the structures of the following compounds.

(i) 3-Methylbutanal (ii) p-Nitropropiophenone

(iii) p-Methylbenzaldehyde (iv) 4-Methylpent-3-en-2-one

(v) 4-Chloropentan-2-one (vi) 3-Bromo-4-phenylpentanoic acid

(vii) p,p'-Dihydroxybenzophenone (viii) Hex-2-en-4-ynoic acid

Name the following compounds according to IUPAC system of nomenclature:

(i) CH₃CH(CH₃)CH₂CH₂CHO

(ii) CH₃CH₂COCH(C₂H₅)CH₂CH₂Cl

(iii) CH₃CH=CHCHO

(iv) CH₃COCH₂COCH₃

(v) CH₃CH(CH₃)CH₂C(CH₃)₂COCH₃

(vi) (CH₃)₃CCH₂COOH

(vii) OHCC₆H₄CHO-p

What is meant by the following terms? Give an example of the reaction in each case.

(i) Cyanohydrin (ii) Acetal

(iii) Semicarbazone (iv) Aldol

(v) Hemiacetal (vi) Oxime

(vii) Ketal (vii) Imine

(ix) 2,4-DNP-derivative (x) Schiff's base

Which acid of each pair shown here would you expect to be stronger?

(i) CH₃CO₂H or CH₂FCO₂H

(ii)CH₂FCO₂H or CH₂ClCO₂H

(iii) CH₂FCH₂CH₂CO₂H or CH₃CHFCH₂CO₂H

(iv)

Show how each of the following compounds can be converted to benzoic acid.

(i) Ethylbenzene (ii) Acetophenone

(iii) Bromobenzene (iv) Phenylethene (Styrene)

Give the IUPAC names of the following compounds:

(i) PhCH₂CH₂COOH (ii) (CH₃)₂C

Predict the products of the following reactions:

(i)

(ii)

(iii)

(iv)

Arrange the following compounds in increasing order of their reactivity in nucleophilic addition reactions.

(i)Ethanal, Propanal, Propanone, Butanone.

(ii)Benzaldehyde, p-Tolualdehyde, p-Nitrobenzaldehyde, Acetophenone.

Hint:Consider steric effect and electronic effect.

Arrange the following compounds in increasing order of their boiling points.

CH₃CHO, CH₃CH₂OH, CH₃OCH₃, CH₃CH₂CH₃

Write the structures of products of the following reactions;

i)

(ii)

(iii)

(iv)

Write the structures of the following compounds.

(i) α-Methoxypropionaldehyde

(ii) 3-Hydroxybutanal

(iii) 2-Hydroxycyclopentane carbaldehyde

(iv) 4-Oxopentanal

(v) Di-sec-butyl ketone

(vi) 4-Fluoroacetophenone