Aldehydes and ketones have lower boiling points than corresponding alcohols. Why?
The boiling points of aldehydes and ketones are lower than that of corresponding alcohols and acids due to absence of intermolecular H–bonding in aldehydes and ketones.
Give simple chemical tests to distinguish between the following pair of compounds :
Ethanal and propanal
Ethanal and propanal can be distinguished by iodoform test. Yellow precipitate of iodoform will be formed from ethanal on heating with iodine and sodium hydroxide solution whereas propanol will not give iodoform test.
Give chemical tests to distinguish between the following pairs of compunds :
Benzaldehyde and acetophenone. Benzaldehyde and acetophenone can be distinguished by Tollens’ test. Benzaldehyde will form silver mirror, on treatment with Tollens’ reagent whereas acetophenone will not show Tollens’ test.
Describe the following reactions :
(i) Acetylation
(ii) Aldol condensation
(i) Acetylation : Introduction of acetyl group 
in alcohols, phenols or
amines is called acetylation.
(ii) Aldol condensation : Two molecules of an aldehyde or ketones having at least one ∝-hydrogen atom condense in the presence of a dilute alkalito give β-hydroxyaldehyde or b-hydroxyketone which upon heating give ∝,β-unsaturated aldehyde or ketone.
Although phenoxide ion has more number of resonating structures than carboxylate ion, carboxylic acid is a stronger acid than phenol. Give two reasons.
Phenoxide ion has the following resonating structures :
Carboxylate ion has the following resonating structures.
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
Ans. (i) By Tollen’s test
Propanal reduces Tollen’s reagent, fehling solution, Benedict solution but propanone
(ketone) does not reduces.
(b) Iodoform test :
Propanone 
gives iodoform test but propanal (CH3-CH2-CHO) does not.
(ii) Acetophenone and Benzophenone can be distinguished using the iodoform test.
Acetophenone gives iodoform test but benzophenone does not.
(iii) Phenol and benzoic acid can be distinguished by ferric chloride test and NaHCO3 test.
(a) Phenol gives voilet colour with FeCl3.
(b) Benzoic acid gives CO2 with NaHCO3 while phenol does not.
(iv) Benzoic acid and Ethyl benzoate can be distinguished by sodium bicarbonate test.
Sodium bicarbonate test :
Benzoic acid react with NaHCO3 to produce brisk effervescence due to the evolution of CO2
gas but ethylbenzoate does not.
(v) Pentan-2-one and pentan-3- one can be distinguished by iodoform test. Pentan-2-one gives iodoform test but pentan-3-one does not.
(vi) Benzaldehyde and acetophenone can be distinguished by the (a) Tollen’s test (b) Iodoform test. Benzaldehyde gives Tollen’s test where as acetophenone gives iodoform test.
(vii) Ethanal and propanal can be distinguished by iodoform test. Ethanal gives iodoform test but propanal does not.
Write the reactions involved in the following :
(i) Etard reaction
(ii) Stephen reduction
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
Which of the following compounds does not reduce fehling’s solution?
(i) C6H5CHO (ii) CH3CHO (iii) CH3COCH2OH (iv) HCOOH
Ans (iv) HCOOH
The correct order of increasing acidic strength is _____________.
(i) Phenol < Ethanol < Chloroacetic acid < Acetic acid
(ii) Ethanol < Phenol < Chloroacetic acid < Acetic acid
(iii) Ethanol < Phenol < Acetic acid < Chloroacetic acid
(iv) Chloroacetic acid < Acetic acid < Phenol < Ethanol
Ans (iii) Ethanol < Phenol < Acetic acid < Chloroacetic acid
The reagent which does not react with both, acetone and benzaldehyde.
(i) Sodium hydrogensulphite (ii) Phenyl hydrazine
(iii) Fehling.s solution (iv) Grignard reagent
Ans (iii) Fehling.s solution
In Clemmensen Reduction carbonyl compound is treated with _____________.
(i) Zinc amalgam + HCl (ii) Sodium amalgam + HCl
(iii) Zinc amalgam + nitric acid (iv) Sodium amalgam + HNO3
Ans (i) Zinc amalgam + HCl
Iodoform test is not given by
(i) Ethanol (ii) Ethanal
(iii) Pentan-2-one (iv) Pentan-3-one
Ans (iv) Pentan-3-one
Iodoform test in not given by
(A) Ethanol (B) Ethanal (C) Pentan-2-one (D) Pentan-3-one
Ans. (D)
Give reasons :
(i) Benzoic acid is a stronger acid than acetic acid.
(ii) Methanal is more reactive towards nucleophilic addition reaction than ethanal.
Ans. (i) Due to the electron donating inducting effect (+I) by the alkyl group on acetic acid destabilise the conjugate base of acetic acid.
(ii) Aldehyde which is a functional group (CHO) is more reactive due to less steric effect.
Give a simple chemical test to distinguish between propanal and propanone.
Propanal being an aldehyde reduces Fehling’s solutions to a red-brown ppt of Cu2O, but
propanone being a keton does not. Propanone being a ketone does not.
Propanal being an aldehye reduces Tollen’s reagent to a silver mirror but propanone being a
ketone does not.