RBSE Class 12 Chemistry Important Questions Chapter 12 Aldehydes, Ketones and Carboxylic Acids

Rajasthan Board RBSE Class 12 Chemistry Important Questions Chapter 12 Aldehydes, Ketones and Carboxylic Acids Important Questions and Answers.

RBSE Class 12 Chemistry Chapter 12 Important Questions Aldehydes, Ketones and Carboxylic Acids

Question 1. 
Which compound produces acetaldehyde on heating with aqueous potassium hydroxide:
(a) CH₃COCl
(b) CH₃CH₂Cl
(c) CH₂ClCH₂Cl
(d) CH₃CHCl₂
Answer:
(d) CH₃CHCl₂

Question 2. 
General formula of aliphatic aldehyde is:
(a) CnH_{2n + 2^O}
(b) CnH_2nO
(c) CnH_2n-2^O
(d) CH_2n-1^O
Answer:
(b) CnH_2nO

Question 3. 
Whose aqueous solution is formalin?
(a) Formic acid
(b) Formaldehyde
(c) Fluorine
(d) Furfural
Answer:
(b) Formaldehyde

 

Question 4. 
Which of the following can differentiate between aldehyde and ketone:
(a) Fehling solution
(b) Hydrazine
(c) Pyrogallol
(d) Grignard Reagent
Answer:
(a) Fehling solution

Question 5. 
Formaldehyde on heating with KOH gives:
(a) Acetylene
(b) Methane
(c) Methanol
(d) Ethyl Formate
Answer:
(c) Methanol

Question 6. 
Aldehyde on oxidation:
(a) Acid
(b) Ether
(c) Seleniumdioxide 
(d) Alcohol
Answer:
(a) Acid

Question 7. 
Dry calcium acetate on heating gives:
(a) acetic acid
(b) acetaldehyde
(c) acetone
(d) ethane
Answer:
(c) acetone

Question 8. 
Formaldehyde on reacting with ammonia gives: 
(a) Paraformaldehyde 
(b) Urotropin
(c) Formose
(d) Bakelite
Answer:
(b) Urotropin

Question 9. 
The compound which gives iodoform test:
(a) Pentane-1-one
(b) Pentane-2-one
(c) Pentane-3-one
(d) Pentanal
Answer:
(b) Pentane-2-one

Question 10. 
Which of the following does not give Cannizzaro reaction:
(a) trimethyl acetaldehyde
(b) benzaldehyde
(c) acetaldehyde
(d) formaldehyde
Answer:
(c) acetaldehyde

Question 11. 
Which of the following is chloral:
(a) CCl₃CH₃
(b) Cl₂CHCOOH
(c) CCl₃CHO
(d) Cl₃CCOOH
Answer:
(c) CCl₃CHO

Question 12. 
Which of the following does not have -OH group:
(a) alcohol
(b) phenol
(c) aldehyde
(d) carboxylic acid
Answer:
(c) aldehyde

Question 13. 
Benedict's solution has:
(a) Ag⁺
(b) La⁺
(c) Cu²⁺
(d) Ba²⁺
Answer:
(c) Cu²⁺

Question 14. 
From which formaldehyde reacts and form bakelite:
(a) Phenol
(b) Chlorobenzene
(c) Nitrobenzene
(d) Aniline
Answer:
(a) Phenol

Question 15. 
At room temperature formaldehyde is:
(a) gas
(b) liquid
(c) solid
(d) none of these
Answer:
(a) gas

Very Short Answer Type Questions:

Question 1. 
Write the structure of 3-oxopentanal.
Answer:

Question 2. 
Write the structural formula of 1-phenylpentan-1-one.
Answer:1
-Phenylpentan-1-one

Question 3. 
Draw the structural formula of 1-phenyl propan- 1-one molecule.
Answer:1

Question4. 
What is Tollen's reagent? Write one usefulness of this reagent.
Answer:
Ammonial silver nitrate solution is called Tollen's reagent.
Uses: It is used to test aldehydes. Both aliphatic and aromatic aldehydes reduce Tollen's reagent to shining silver mirror. It is also used to distinguish aldehydes from ketones.

Question 5. 
Draw the structure of 3-methylbutanal.
Answer:

Question 6. 
Draw the structure of 4-chloropentan-2-one.
Answer:

Question 7. 
Arrange the following compounds in increasing order of their reactivity in nucleophilic addition reactions ethanal, propanal, propanone, butanone. 
Answer:
Butanone < Propanone < Propanal< Ethanal 

Question 8. 
Write the IUPAC name of the following:

Answer:
IUPAC name: Pent-2-enal

Question 9. 
Write the IUPAC name of Ph-CH=CH-CHO.
Answer:
IUPAC name: 3-phenylprop-2-enal.

Question 10. 
Give a chemical test to distinguish between Benzoic acid and Phenol.
Answer:
Benzoic acid forms a brisk effervescence with NaHCO₃ solution but phenol does not respond to this test.

Question 11. 
Give a chemical test to distinguish between Ethanal and Propanal. 
Answer:
Ethanal on heating with 12 in NaOH gives a yellow ppt of iodoform but propanal does not respond to this test.

Question 12. 
Give a chemical test to distinguish between Propanal and Propanone. 
Answer:
Propanone on reacting with 12 and NaOH gives a yellow ppt of iodoform but propanal does not respond to this test.

Question 13. 
Formaldehyde does not take part in Aldol condensation. Why? 
Answer:
Formaldehyde does not contain a-hydrogen atom. Therefore it does not take part in aldol condensation. 

Question 14. 
Write the IUPAC name of the following:

Answer:
IUPAC name 2-methylcyclohexanone

Question 15. 
Aldehydes and Ketones have lower boiling points than corresponding alcohols. Why?
Answer:
It is due to weak molecular association in aldehydes and ketones arising out of the dipole dipole interactions.

Question 16. 
Give the structure and IUPAC name of the product formed when propanone is reacted with methylmagnesium bromide followed by hydrolysis.
Answer:

IUPAC name: 2-methylpropan-2-ol.

Question 17. 
Write the structure of the product formed in the following reaction:

Answer:

Question 18. 
Write the structure of 3-methylbutanal.
Answer:

Question 19. 
Write the structure of 4-chloropentan-2-one.
Answer:

Question 20. 
Write the structure of p-Methylben-zaldehyde molecule.
Answer:

Question 21. 
Rearrange the following compounds in the increasing order of their boiling points: 
CH₃ –CHO, CH₃ –CH₂– OH, CH₃ – CH₂ - CH₃ 
Answer:
CH₃CH₂CH₃ < CH₃CHO < CH₃CH₂OH

Question 22. 
Ethanal is soluble in water. Why?
Answer:
Ethanal is soluble in water due to H-bonding between the polar carbonyl group and water molecules. 

Question 23. 
Draw the structure of the compound named 4-methylpent-3-en-2-one. 
Answer:
4-Methylpent-3-en-2-one

Question 24. 
Carboxylic acids do not give characteristic reactions of carbonyl group. Explain why? 
Answer:
The carboxylic carbon is less electrophilic than carbonyl carbon because of the possible resonance structure.

Question 25. 
Give a chemical test to distinguish between benzoic acid and phenol.
Answer:
On addition of NaHCO₃ to both solutions carbon dioxide gas is evolved with benzoic acid while phenol does not form CO₂

Question 26. 
Write IUPAC name of the following.

Answer:
IUPAC name: 2-Ethyl cyclohexanone. 

Question 27. 
Write the IUPAC name of the compound.

Answer:
IUPAC name: 3-Hydroxybutanoic acid 

Question 28. 
Write the IUPAC name of the compound.

Answer:
IUPAC name: 3-Aminobutanal

Question 29. 
Write the IUPAC name of the compound

Answer:
IUPAC name: 4-Hydroxypontan-2-one 

Question 30. 
Write the structure of p-methylben-zaldehyde.
Answer:
p-methylbenzaldehyde

Question 31. 
Write the structure of 4-chloropentan-2-one.
Answer:
4-Chloropentan-2-one:

Question 32. 
Write the structure of 2-hydroxybenzoic acid.
Answer:
2-hydroxybenzoic acid:

Question 33. 
Write the IUPAC name of the following compound:

Answer:
IUPAC name: 2-methylpropanal

Question 34. 
Give a test to distinguish between propan-2- one and pentan-3-one.
Answer:
Propan-2-one and pentan-3-one can be distinguished by lodoform test.

Question 35. 
Draw the structure of 3-methylpentanal.
Answer:

Question 36. 
Write the IUPAC name of the following.
CH₃ – CH₂ – CHO
Answer:
IUPAC name: Propan-1-al

Question 37. 
Draw the structure of 2-methylbutanal.
Answer:

Question 38. 
What type of aldehydes undergo Cannizzaro reaction? 
Answer:
Aldehydes which do not contain a-hydrogen atom undergo Cannizzaro reaction e.g Formaldehyde (HCHO) and Benzaldehyde (C₆H₅CHO).

Question 39. 
What type of aldehydes undergo Aldol condensation? 
Answer:
Aldehydes with a hydrogen atom undergo Aldol condensation.

Question 40. 
Arrange the following compounds in the increasing order of their property indicated:
Propanol. Propane, Propanal (boiling point)
Answer:
Propanol > Propanal > Propane (Boiling point)

Short Answer Type Question:

Question 1. 
Name the reagents used in the following reactions: 

Answer:
(i) LIAIH₄ (Lithium Aluminium hydride) 
(ii) KMnO₄ (Alkaline Potassium permanganate)

Question 2. 
Write the reagents required in the following reactions: 

Answer:

Question 3. 
Arrange the following compounds in increasing order of their property as indicated:
(i) CH₃COCH, C₆H₅COCH₃, CH₃CHO
(reactivity towards nucleophilic addition)
(ii) Cl - CH₂ - COOH, F - CH₂ - COOH, CH₃ - COOH (acidic character)
Answer:

Question 4. 
Write the equations involved in the following reactions:
(i) Wolff-Kishner reduction
(ii) Etard reaction
Answer:
(i) Wolff-Kishner reduction

(ii) Etard reaction 

Question 5. 
Write the reactions involved in the following:
(i) Hell-Volhard Zelinsky reaction 
(ii) Decarboxylation reaction
Answer:

Question 6. 
Write the reactions involved in the following reactions:
(i) Clemmensen reduction
(ii) Cannizzaro reaction
Answer;
(i) Clemmensen reduction: The carbonyl group of aldehydes and ketones is reduced to CH₂ group on treatment with zinc amalgam and concentrated hydrochloric acid.

(ii) Cannizzaro reaction: Aldehydes, which do not have an a hydrogen atom undergo self oxidation and reduction on treatment with conc. alkali and produce alcohol and carboxylic acid salt.

Question 7. 
Predict the products of the following reactions:

Answer:

Question 8. 
Predict the products of the following reactions:

Answer:

Question 9. 
Write structures of compounds A, B and C in cach of the following reactions:

Answer:

Question 10. 
Do the following conversions in not more than two steps:
(i) Benzoic acid to benzaldehyde
(ii) Ethyl benzene to Benzoic acid
(iii) Propanone to Propene
Answer:

Long Answer Type Questions:
 
Question 1. 
(a) How are the following obtained? 
(i) Benzoic acid from ethyl benzene. 
(ii) Benzaldehyde from toluene. 
(b) Complete each synthesis by giving the missing material, reagent or products: 

Answer:
(a) (i) Benzoic acid from ethyl benzene: 

(ii) Benzaldehyde from toluene: It can be obtained by Etard reaction. 

It is also known as Friedel Crafts acetylation reaction. 

Question 2. 
(a) Write chemical equations to illustrate the following name reactions: 
(i) Cannizzaro reaction 
(ii) Hell-Volhard-Zelinsky reaction 
(b) Give chemical tests to distinguish between the following pairs of compounds: 
(i) Propanal and Propanone 
(iii) Phenol and Benzoic acid 
Answer:
(a) (i) Cannizzaro reaction is a chemical reaction named after Stanislao Cannizzaro that involves the base-induced disproportionation of two molecules of a non-enolizable aldehyde to yield a carboxylic acid and a primary alcohol.

(ii) Hell-Volhard-Zelinsky reaction: Carboxylic acid reacts with chlorine or bromine in presence of small quantities of red phosphorus to give exclusively a-chloro or a-bromo acids. 
Example: 

 
(b) (i) Propanal and Propanone: Propanal gives positive test with Fehling solution in which a red ppt. of cuprous oxide is obtained while propanone does not respond to test. 

(ii) Acetophenone and Benzophenone: They can be distinguished by iodoform test which is given by only acetophenone with the formation of yellow ppt. while benzophenone does not respond to iodoform test. 

 
(iii) Phenol and Benzoic acid : On addition of NaHCO₃ to both solutions carbon dioxide gas is evolved with benzoic acid while phenol does not form CO₂. 

Question 3. 
(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 C₆H₆O₂. It gets hydrolysed with dilute sulphuric acid and gives a carboxylic acid B and an alcohol C. Oxidation of C with chromic acid also produces, B. C on dehydration reaction gives but-1-ene. Write equations for the reactions involved. 
Answer:
(a) (i) Ethanol to 3-hydroxybutanal: 

(ii) Benzaldehyde to Benzophenone 

(b) The compound A with molecular formula is Butyl butanoate. 

Question 4. 
(a) Give chemical tests to distinguish between compounds in the following pairs of substances: 
(i) Ethanol and Propanal 
(ii) Benzoic acid and Ethyl benzoate 
(b) 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 Tollen's reagent but forms an addition compound with sodium hydrogen sulphite and gives positive iodoform test. On vigorous oxidation it gives ethanoic and propanoic acids. Derive the structure of the compound. 
Answer:
(a) (i) Ethanol and Propanal: 
Ethanol: Ethanol does not form silver mirror with Tollen's reagent. 
Propanal: Propanal being an aldehyde forms silver mirror with Tollen's reagent (Silver mirror Test). 

(ii) Benzoic acid and Ethyl benzoate : 
By lodoform test: Ethyl benzoate on boiling with excess of NaOH solution gives ethyl alcohol which on heating with iodine gives yellow ppt of iodoform. 

Benzoic acid does not show this test. 

(b) % oxygen = 100 - (%C + %H)
= 100 - (69.77 + 116) = 18.6%

Thus, empricial formula of the compound = C5H10O
∴ Empirical formula mass = 5 x 12 + 10 x 1 + 1 x 16 = 86

= \(\frac{86}{86}\) = 1
∴ Molecular formula = n x Empirical formula = C₅H₁₀O

Step II : To determine the structure of the compound
(i) Since the given compound forms addition compound with NaHSO₃ therefore it must be either an aldehyde or methyl ketone.
(ii) As the compound does not reduce Tollen's reagent therefore it can not be an aldehyde and hence it must be a methyl ketone.
(iii) Since the given compound gives positive iodoform test, therefore the given compound is a methyl ketone.
(iv) Since the given compound on vigorous oxidation gives a mixture of ethanoic acid and propanoic acid therefore the methyl ketone is pentan-2-one.

Step III : To explain the reactions involved in the given problem:

Question 5. 
(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) CH₂CH₂CH(Br)COOH, CH₂CH(Br) CH₂COOH (CH₃)₂CHOOH,CH₃CH₂CH₂COOH (acid strength) 
(b) How would you bring about the following conversions: 
(i) Propanone to Propene 
(iii) Bromobenzene to 1-phenylethanol. 
(ii) Benzoic acid to Benzaldehyde 
Answer:
(a) (i) 4-Methoxy benzoic acid < Benzoic acid < 4-Nitrobenzoic acid < 3, 4-Dinitrobenzoic acid. The order is due to increasing -I effect. 

The above order is due to increased-I effect with decrease of distance and decrease of +I effect. 
(b) (i) Propanone to Propene 

(ii) Benzoic acid to Benzaldehyde (Rosenmund reduction) 

 
(iii) Bromobenzene to 1-phenylethanol 

Question 6. 
(a) Explain the mechanism at a nucleophilic attack on the carbonyl group of an aldehyde or a ketone. 
(b) An organic compound (A) (molecular formula C.H₁₆O₂) was hydrolysed with dilute sulphuric acid to give a carboxylic acid (B) and an alcohol (C). Oxidation of (C) 
Answer:
(a) Mechenishm of a nucleophilic attack on the carbonyl group C = O is a polar group in which carbon acquires positive charge and O acquires negative charge due to more electronegativity of oxygen. The Nu attacks on carbon and forms a tetrahedral intermediate and then electrophile attacks on axygen and forms a compound. 

(b) Since the organic compound (A) with molecular formula (M.F.) CHO₂ upon hydrolysis with dil. H₂SO₄ gives carboxylic acid (B) and the alcohol (C) therefore it must be an ester. Further since oxidation of (C) with chronic acid produces the acid (B), therefore both the carboxylic acid (B) and the alcohol (C) must contain the same number of carbon atoms. 

Question 7. 
(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) Ethanal and Propanal: Ethanal and propanal can be distinguished by iodoform test. Warm each compound with iodine and sodium hydroxide solution in water. Ethanal gives yellow crystal of iodoform while propanal does not respond to iodoform test. 

(ii) Phenol and Benzoic acid : On addition of NaHCO₃ to both solutions, carbon dioxide gas is evolved with benzoic acid while phenol does not form CO₂. 

(b) (i) Benzoic acid to benzaldehyde : 

(ii) Ethanal to but-2-enal 

(iii) Propanone to propene 

Question 8. 
(a) Illustrate the following name reactions giving a chemical equation in each case: 
(i) Clemmensen reaction 
(ii) Cannizzaro reaction 
(b) Describe how the following conversions can be brought about: 
(i) Cyclohexanol to cyclohexan-1-one 
(ii) Ethylbenzene to benzoic acid 
(iii) Bromobenzene to benzoic acid 
Answer:
(a) (i) Clemmenson's reduction is most commonly used to convert acyl benzenes to alkyl benzenes. - Benzaldehyde undergoes Clemmenson's reduction in the presence of zinc amalgam and concentrated hydrochloric acid to form toluene.


(ii) Cannizzaro reaction is a chemical reaction named after Stanislao Cannizzaro that involves the base-induced disproportionation of two molecules of a non-enolizable aldehyde to yield a carboxylic acid and a primary alcohol.


(b) (i) Cyclohexanol to cyclohexan-1-one 

(ii) Ethylbenzene to benzoic acid 

(iii) Bromobenzene to benzoic acid 

Question 9. 
(a) Illustrate the following name reactions 
(i) Hell-Volhard-Zelinsky reaction 
(ii) Wolff-Kishner reduction 
(b) How are the following conversions carried out : 
(i) Ethylcyanide to ethanoic acid
(ii) Butan-1-ol to butanoic acid  
(iii) Methylbenzene to benzoic acid 
Write chemical equations for the involved reactions. 
Answer:
(a) (i) Hell-Volhard-Zelinsky reaction: Carboxylic acid reacts with chlorine or bromine in presence of small quantities of red phosphorus to give exclusively a-chloro or a-bromo acids. 
Example: 

(ii) Wolff-Kishner reduction: The reduction of aldehydes and ketones to the corresponding hydrocarbons by heating them with hydrazine and KOH or potassium tert-butoxide in a high boiling solvent like ethylene glycol is called Wolff- Kishner reduction. 

(b) (i) Ethylcyanide to ethanoic acid 

(ii) Butan-1-ol to butanoic acid 

(iii) Methylbenzene to benzoic acid 

Question 10. 
(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 conversions carried out? 
(i) Ethylcyanide to ethanoic acid 
(ii) Butan-1-ol to butanoic acid 
(iii) Benzoic acid to m-bromobenzoic acid. 
Answer:
(a) (i) Clemmenson's reduction is most commonly used to convert acyl benzenes to alkyl benzenes. - Benzaldehyde undergoes Clemmenson's reduction in the presence of zinc amalgam and concentrated hydrochloric acid to form toluene.

(ii) Hell-Volhard-Zelinsky reaction: Carboxylic acid reacts with chlorine or bromine in presence of small quantities of red phosphorus to give exclusively a-chloro or a-bromo acids. 
Example: 

(b) (i) Ethylcyanide to ethanoic acid 

(ii) Butan-1-ol to butanoic acid 

(iii) Benzoic acid to m-bromobenzoic acid 

Question 11. 
(a) Illustrate the following reactions giving a suitable example for each. 
(i) Cross aldol condensation 
(ii) Decarboxylation. 
(b) Give simple tests to distinguish between the following pairs of compounds : 
(i) Pentan-2-one and Pentan-3-one 
(ii) Benzaldehyde and Acetophenone 
(iii) Phenol and Benzoic acid 
Answer:
(a) (i) Cross aldol condensation: When aldol condensation is carried out between two different aldehydes and or ketones, it is called cross aldol condensation. 

(ii) Decarboxylation : Carboxylic acids lose carbon dioxide to form hydrocarbons when their sodium salts are heated with soda lime. The reaction is known as 

(b) (i) Pentan-2-one and Pentan-3-one 
By Iodoform test: 

Add I₂ and NaOH in both the solutions Pentan-2-one gives yellow coloured precipitate, but pentan-3-one does not.

(ii) Benzaldehyde and Acetophenone lodoform test: Warm each organic compound with I, and NaOH solution. Acetophenone forms yellow precipitate of iodoform. Benzaldehyde does not respond to this test. 

(iii) Phenol and Benzoic acid: On addition of NaHCO₃ to both with solutions, carbon dioxide gas is evolved benzoic acid while phenol does not form CO₂. 

Question 12. 
(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-trimethylcyclohexanone does not. 
(b) An organic compound with molecular formula C₉H_1O forms 2, 4, - DNP derivative, reduces Tollens reagent and undergoes Cannizzaro reaction. On vigorous oxidation it gives 1, 2-benzene dicarboxylic acid. Identify the compound. 
Answer:
(a) (i) Because one of the -NH, in semicarbazide is involved in the resonance with group. 

(ii) Due to steric hinderance in 2. 4. 6-trimethylcyclohexanone, it doesn't react with HCN easily. 

But the yield of the product is very less. 

(b) Compound C₉H₁₀O, forms 2, 4-DNP derivative, so it contains a carbonyl group. Also it reduces Tollens reagent therefore carbonyl group is an aldehyde group. Since it undergoes Cannizzaro's reaction, aldehyde has no a-hydrogen atom, so compound is C₈H₉ CHO. On vigorous oxidation, compound gives 1, 2-benzene dicarboxylic acid hence the compound is 

Question 13. 
(a) Give chemical tests to distinguish between 
(i) Phenol and Benzoic acid 
(b) Write the structures of the main products of following reactions: 

Answer:
(i) Phenol and Benzoic acid : On addition of NaHCO₃ to both solutions carbon dioxide gas is evolved with benzoic acid while phenol does not form CO₂. 

(ii) Acetophenone and Benzophenone: They can be distinguished by iodoform test which is given by only acetophenone with the formation of yellow ppt. while benzophenone does not respond to iodoform test. 

Question 14. 
(a) Write a suitable chemical equation to complete each of the following transformations: 
(i) Butan-1-ol to butanoic acid 
(ii) 4-Methylacetophenone to benzene-1, 4-dicarboxylic acid. 
(b) An organic compound with molecular formula C₉H₁₀O forms 2, 4-DNP derivative, reduces Tollen's reagent and undergoes Cannizzaro reaction. On vigorous oxidation it gives 1, 2-benzenedicarboxylic acid. Identify the compound. 
Answer:
(a) (i) Butan-1-ol to butanoic acid: 

(ii) 4-Methylacetophenone to benzene-1, 4-dicarboxylic acid : 

(b)  C₉H₁₀O, forms 2, 4-DNP derivative, so it contains a carbonyl group. Also it reduces Tollens reagent therefore carbonyl group is an aldehyde group. Since it undergoes Cannizzaro's reaction, aldehyde has no a-hydrogen atom, so compound is C₈H₉ CHO. On vigorous oxidation, compound gives 1, 2-benzene dicarboxylic acid hence the compound is 

Question 15. 
(a) Give chemical tests to distinguish between: 
(i) Propanol and propanone 
(ii) Benzaldehyde and acetophenone. 
(b) Arrange the following compounds in an increasing order of their property as indicated: 
(i) Acetaldehyde, Acetone, Methyl tert-butyl ketone (reactivity towards HCN) 
(ii) Benzoic acid, 3,4-Dinitrobenzoic acid, 4-Methoxybenzoic acid (acid strength) 
(iii) CH₃CH₂CO(Br)COOH, CH₃CH(Br)CH₂COOH, (CH₃)₂CHCOOH (acid strength) 
Answer:
(a) (i) Propanone and Propanol: 
 It can be done by lodoform test where propanone gives yellow ppt. of iodoform while propanol does not respond to  test.

(ii) Benzaldehyde and acetophenone: 
By Iodoform test: Acetophenone being a methyl ketone on treatment with I₂/NaOH acetophenone undergoes iodoform test to give yellow ppt. of lodoform but benzaldehyde does not. 

(b) (i) Methyl tert-butyl ketone< Acetone < Acetaldehyde 
(ii) 4-Methoxybenzoic acid < Benzoic acid < 3, 4-Dinitro benzoic acid 

Question 16. 
(a) An organic compound A' with molecular formula C₈H₈O forms an, orange red precipitate with 2, 4-DNP reagent and given yellow precipitate on heating with I₂, and NaOH. It neither reduces Tollen's reagent nor Fehling's reagent nor does it decolourizes bromine water or Baeyer's reagent. On drastic oxidation with chromic acid, it gives a carboxylic acid "having molecular formula C₇H₆O₂. Identity the compounds A' and 'B' and explain the reactions involved. 
(b) Write the mechanism of esterification of carboxylic acids. 
Answer:
(a) (i) Molecular formula: C₈H₈O. 
(ii) Since it gives orange red ppt with 2, 4-DNP reagent.  Therefore it must be either aldehyde or a ketone. 
(iii) Since, it does not reduce Tollen's reagent nor Fehling's reagent, solution “A must be a ketone. Therefore, it must › be a methyl ketone. 
(iv) 'A' on treatment with I₂/NaOH gives yellow ppt. Therefore, it must be a methyl ketone
(v) It does not decolorise Br₂, water or Baeyer's reagent so the unsaturation of 'A' is due to benzene ring. Therefore the structure of A should be as 

Reactions: 

(b) Mechanism of esterification of carboxylic acids : 

Question 17. 
(a) An organic compound A' which has characteristic odour, on treatment with NaOH forms two compounds B' and 'C. Compound 'B' has the molecular formula C₇H₈O which on oxidation with CrO₃, gives back compound ‘A. Compound 'C is the sodium salt of the acid. 'C when heated with soda lime yields an aromatic hydrocarbon D. Deduce the structures of 'A', 'B', 'C' and 'D'. 
(b) Give reasons: 
(i) Electrophilic substitution in Benzoic acid takes place at meta position. 
(ii) Carboxylic acids do not give characteristic reactions of carbonyl group. 
Answer:
(a) (A) gives characteristic odour which on treatment with NaOH and forms two compounds B and C 
(A) should be benzaldehyde
Reactions: 

 
(b) (i) The benzene ring of benzoic acid undergoes electrophilic substitution reaction such as nitration, sulphonation etc. Since the -COOH group in benzene is an electron withdrawing group, therefore it is meta directing group. 
(ii) The carboxylic carbon is less electrophilic than carbonyl carbon because of the possible resonance structure. 

Question 18. 
(a) Give chemical tests to distinguish between the following pairs of compounds: 
(i) Benzene amide and 4-aminobenzoic acid 
(ii) Methyl acetate and Ethyl acetate 
(b) An organic compound with molecular formula C₉H₁₀O forms 2. 4-DNP derivative and reduces Tolien's reagent and undergoes Cannizzaro's reaction. On vigorous oxidation, it gives 1.2 benzenedicarboxylic acid. Identify the compound and write chemical equations for the reactions. 
Answer:
(a) (i) NaHCO₃, test: p-Aminobenzoic acid is an acid which decomposes NaHCO₃, solution to produce effervescence due to evolution of CO₂ gas while benzene amide does not give this test. 
(ii) Ethyl acetate when boiled with exces of NaOH gives ethyl alcohol and if it is heated with I₂, and NaOH solution, it gives yellow precipitate of iodoform. Methyl acetate on hydrolysis with NaOH gives methyl alcohol which does not respond to iodoform test. 

(b) (i) Molecular formula of compound: C₉H₁₀O 
(ii) It forms a 2,4-DNP derivative and reduces Tollen's reagent. It must be an aldehyde. 
(iii) Since it undergoes Cannizzaro reaction, therefore CHO group is directly attached to the benzene ring. 
(iv) On oxidation it gives 1,2-benzenedicarboxylic acid, therefore it must be an ortho-substituted benzaldehyde, so the structure should be 

Reaction:

Question 19. 
(a) Give chemical tests to distinguish between the following pairs of compounds: 
(i) Benzoic acid and Phenol 
(ii) Benzaldehyde and Acetophenone 
(b) An organic compound with molecular formula C₅H₁₀O does not reduce Tollen's reagent but forms an addition compound with sodium hydrogen sulphite and gives a positive iodoform test. On vigorous oxidation, it gives ethanoic acid and propanoic acid, identify the compound and write all chemical equations for the reactions. 
Answer:
(a) Phenol and Benzoic acid: On addition of NaHCO₃ to both with solutions, carbon dioxide gas is evolved benzoic acid while phenol does not form CO₂. 

(ii) Benzaldehyde and Acetophenone lodoform test: Warm each organic compound with I, and NaOH solution. Acetophenone forms yellow precipitate of iodoform. Benzaldehyde does not respond to this test. 
 
(b) (i) Molecular formula of compound: C₅H₁₂O. 
(ii) It gives an addition product with NaHSO₃, so it must be either an aldehyde or methyl ketone. 
(iii) It does not reduce Tollen's reagent so it is not an aldehyde. 
(iv) It gives + ve iodoform test, therefore it is methyl ketone. 
(v) On oxidation it gives a mixture of ethanoic acid and propanoic acid. Therefore, possible structure is pentan-2-one. 

Reactions: 

Question 20. 
(a) Although phenoxide ion has more number of resonating structures than carboxylate ion, carboxylic acid is a stronger acid than phenol. Give two reasons. 
(b) How will you bring about the following converstions? 
(i) Propanone to propane 
(iii) Ethanal to but-2-enal 
(ii) Benzoyl chloride to benzaldehyde 
Answer:
(a) Carboxylic acid is a stronger acid than phenol because: 
(i) In the resonating structure of phenol and carboxylic acid, the negative charge on the carboxylate ion is delocalised over two oxygen atoms while they are localized on oxygen atom. 

(ii) The release of a proton from carboxylic acids is much easier than from phenols. 
(b) (i) Propanone to Propane 

(ii) Benzoyl chloride to Benzaldehyde (Rosenmund reduction) 

(iii) (i) The benzene ring of benzoic acid undergoes electrophilic substitution reaction such as nitration, sulphonation etc. Since the -COOH group in benzene is an electron withdrawing group, therefore it is meta directing group. 
(ii) The carboxylic carbon is less electrophilic than carbonyl carbon because of the possible resonance structure. 

Question 21. 
(a) Complete the following reactions: 

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

(b) (i) Ethanal and Propanal: Ethanal and propanal can be distinguished by iodoform test. Warm each compound with iodine and sodium hydroxide solution in water. Ethanal gives yellow crystal of iodoform while propanal does not respond to iodoform test. 

(ii) Phenol and Benzoic acid: On addition of NaHCO₃ to both with solutions, carbon dioxide gas is evolved benzoic acid while phenol does not form CO₂. 

Question 22. 
(a) How will you convert the following: 
(i) Propanone to Propan-2-ol 
(ii) Ethanal to 2-hydroxy propanoic acid 
(iii) Toluene to benzoic acid 
(b) Give simple chemical test to distinguish between: 
(i) Pentan-2-one and Penton-3-one 
(ii) Ethanal and Propanal 
Answer:
(a) (i) Propanone to Propan-2-ol 

(ii) Ethanal to 2-hydroxy propanoic acid 

(iii) Toluene to Benzoic acid 

(b) (i) Pentan-2-one and Pentan-3-one By iodoform test: 

Add I₂, and NaOH in both the solutions. Pentan 2-one gives yellow coloured precipitate, but pentan 3-one does not. 
(ii) Ethanal and Propanal : Add I, and NaOH in both the solutions. Ethanal gives yellow coloured precipitate but propanal does not. 

Question 23. 
(a) Write the products of the following reactions: 

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

Answer:
(a) (i) Clemmensen Reduction: 

(ii) Rosenmund Reaction: 

(iii) Bromination 

(b) (i) Due to much stronger l-effect of F over CI, the FCH₂COO" ion is much more stable than ClCH₂COO ̄ ion and hence FCH₂COOH is a stronger acid than ClCH₂COOH. 

(ii) Ethanoic acid is more stronger acid than phenol due to less pk, than that of phenol and the carboxylate ion is much more resonance stabilized than phenoxide ion. 

Question 24. 
Two moles of organic compound 'A' on treatment with a strong base gives two compounds '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. 

Answer:

∴ A = Formaldehyde, 
B = Methyl alcohol, 
C = Sodium formate, 
D = Formic acid 

Question 25. 
(a) How will you carry out the following conversions? 
(i) Acetylene to Acetic acid 
(ii) Toluene to m-nitrobenzoic acid 
(iii) Ethanol to Acetone 
(b) Give reasons: 
(i) Chloroacetic acid is stronger than acetic acid. 
(ii) pH of reaction should be carefully controlled while preparing ammonia derivatives of carbonyl compounds. 
Answer:
(a) (i) Acetylene to Acetic acid 

(ii) Toluene to m-nitrobenzoic acid 

(iii) Ethanol to acetone 

(b) (i) Because - I effect of CI decrease the electron density in the O-H bond therby making the release of a proton easier. 

(ii) In strongly acidic medium, ammonia derivatives being will react with acid and will not react with carbonyl compound. In basic medium, OH will attack carbonyl group. 

Question 26. 
(a) 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) Benzaldehyde and Benzoic acid 


(ii) Propanal and Propanone:
 

Question 27. 
(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:
(a) (i) Aldehydes are more reactive than ketones due to the following two reasons: 
1. Due to smaller +1 effect of one alkyl group in aldehydes as compared to larger + effect of two alkyl groups, the magnitude of positive charge in the carbonyl carbon is more in aldehydes than in ketones. As a result, nucleophilic addition reactions occur more readily in aldehydes than in ketones. 

2. Due to presence of a H-atom on the carbonyl group, aldehydes can be more easily oxidised than ketones. 
(ii) The release of a proton from carboxylic acid is much easier than phenols because carboxylate ion much more resonance stabilized than phenoxide ion. 

(b) (i) Wolff-Kishner reduction: The reduction of aldehydes and ketones to the corresponding hydrocarbons by heating them with hydrazine and KOH or potassium tert-butoxide in a high boiling solvent like ethylene glycol is called Wolff- Kishner reduction. 

(ii) Aldol condensation : Those aldehydes and ketones with atleast one a-hydrogen atom condense together in presence of dil. alkali eg NaOH etc. to form a B-hydroxy aldehyde or α β-hydroxy ketone respectively which gets dehydrated in the presence of acid upon heating to form a, α β-unsaturated compound. 

(iii) Cannizzaro reaction: Aldehydes, which do not have an a-hydrogen atom undergo self oxidation and reduction on treatment with conc. alkali and produce alcohol and carboxylic acid salt. 

Question 28. 
(a) Write the products formed when CH,CHO reacts with the following reagents: 
(i) HCN 
(iii) CH₃CHO in the presence of dilute NaOH 
(ii) H₂N - OH 
(b) Give simple chemical tests to distinguish between the following pairs of compounds: 
(i) Benzoic acid and Phenol 
(ii) Propanal and Propanone. 
Answer:

(b) (i) Benzoic acid and Phenol: On addition of NaHCO₃ to both solutions, carbondioxide gas is evolved with benzoic acid while phenol does not form CO₂. 

(ii) Propanal and Propanone: Propanal gives positive test with Fehling solution in which a red ppt. of cuprous oxide is obtained while propanone does not respond to test. 

Question 29. 
(a) Account for the following: 
(i) Cl – CH2COOH is a stronger acid than CH3COOH. 
(ii) 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 reaction 
(c) Out of CH₃CH₂-CO-CH₂-CH₃ and CH₃CH₂- CH₂- CO - CH₃ which gives iodoform test? 
Answer:
(a) (i) Because-I effect of Cl decreases the electron density in the O-H bond thereby making the release of a proton  easier. 

(ii) Carboxylic acids do not give the reactions of.carbonyl group as there is no carbonyl group present due to resonance. 

(b) (i) Rosenmund reduction 

(ii) Cannizzaro reaction: Aldehydes, which do not have an a-hydrogen atom undergo self oxidation and reduction on treatment with conc. alkali and produce alcohol and carboxylic acid salt. 

Question 30. 
(a) Draw the structures of the following compounds: 
(i) 4-chloropentan-2-one 
(b) Write the product(s) in the following: 

Answer:

Question 31. 
(a) Write the IUPAC names of the following compounds: 
(i) CH₃CO(CH₂)₄CH₃ 
(ii) Ph.- CH = CH– CHO 
(b) Describe the following conversions in not more than two steps: 
(i) Ethanol to 3-Hydroxybutanal 
(ii) Benzoic acid to m-nitrobenzyl alcohol 
(iii) Propanone to Propene 
Answer:
(a) (i) CH₃CO(CH2)4CH3 
IUPAC name: Heptan-2-one 
(ii) Ph- CH = CH - CHO 
IUPAC name: 3-phenylprop-2-en-1-al 
(b) (i) Ethanol to 3-hydroxybutanal: 


(ii) Benzoic acid to m-nitrobenzyl alcohol: 

 
(iii) Propanone to Propene 

Question 32. 
(a) Draw the structures of the following compounds: 
(i) 4-Chloropentan-2-one 
(ii) p-Nitropropiophenone 
(b) Give tests to distinguish between the following pairs of compounds : 
(i) Ethanal and Propanal 
(ii) Phenol and Benzoic acid 
(iii) Benzaldehyde and Acetophenone 
Answer:
(a) (i) 4-Chloropentan-2-one 

(ii) p-Nitropropiophenone 

(b) (i) Ethanal and Propanal: Ethanal and propanal can be distinguished by iodoform test. Warm each compound with iodine and sodium hydroxide solution in water. Ethanal gives yellow crystal of iodoform while propanal does not respond to iodoform test. 

 (ii) Phenol and Benzoic acid : On addition of NaHCO₃ to both solutions, carbon dioxide gas is evolved with benzoic acid while phenol does not form CO₂. 

(iii) Benzaldehyde and Acetophenone lodoform test: Warm each organic compound with I, and NaOH solution. Acetophenone forms yellow precipitate of iodoform. Benzaldehyde does not respond to this test.

 

Question 33. 
(a) Describe the following giving chemical equations : 
(i) Decarboxylation reaction 
(ii) Friedel-Crafts reaction 
(b) How will you bring about the following conversions? 
(i) Benzoic acid to Benzaldehyde 
(iii) Ethanol to 3-Hydroxybutanal 
(ii) Benzene to m-Nitroacetophenone 
Answer:
(a) (i) Decarboxylation reaction: When sodium salt of carboxylic acid is heated with soda lime (NaOH + CaO), then corresponding alkane and CO₂ will be evolved. 

(ii) Friedel-Crafts reaction: The introduction of alkyl or acetyl group in the presence of anhydrous aluminium chloride (AICl₃) as catalyst to ortho and para positions of an aromatic compound is called Friedel-Crafts reaction. 

(b) (i) Benzoic acid to Benzaldehyde 

(ii) Benzene to m-Nitroacetophenone 

(iii) Ethanol to 3-Hydroxybutanal 

Question 34. 
(a) Describe the following actions: 
(i) Acetylation 
(ii) Aldol condensation 
(b) Write the main product in the following equations: 

Answer:
(a) (i) Acetylation: The addition of aryl (-COCH₃) group on the ortho and para positions of acyl halide in the presence of a Lewis acid i.e. anhydrous aluminium chloride (AICl₃) which acts as a catalyst. 

(ii) Aldol condensation : Those aldehydes and ketones with atleast one a-hydrogen atom condense together in presence of dil. alkali eg NaOH etc. to form a B-hydroxy aldehyde or α β-hydroxy ketone respectively which gets dehydrated in the presence of acid upon heating to form a, α β-unsaturated compound. 

Question 35. 
(a) Draw the structure of the following 
(i) p-Methylbenzaldehyde 
(b) Give chemical tests to distinguish between the following pairs of compounds: 
(i) Benzoic acid and Ethyl benzoate. 
(ii) Benzaldehyde and Acetophenone. 
(iii) Phenol and Benzoic acid. 
Answer:
(a) (i) p-Methylbenzaldehyde : 

(ii) 4-Methylpent 3-en-2-one 

(b) (i) Distinction between Benzoic acid and Ethyl benzoate: 
By Sodium bicarbonate test: Acids react with NaHCO₃ to produce brisk effervescence due to the evolution of CO₂ gas. Benzoic acid being an acid responds to this test, but ethyl benzoate does not. 

(ii) Benzaldehyde and Acetophenone 
By lodoform test: Acetophenone being a methyl ketone on treatment with I₂ and NaOH (NaO) undergoes iodoform test to give yellow ppt. of iodoform on heating whereas benzaldehyde does not. 

(iii) Phenol and Benzoic acid : On addition of NaHCO₃ to both solutions, carbon dioxide is evolved with benzoic acid while phenol does not form CO₂. 

 Question 36. 
(a) Draw the structures of the following derivatives 
(i) Propanone oxime 
(ii) Semicarbazone of CH₃CHO 
(b) How will you convert ethanal into the following compounds? Give the chemical equations involved. 

Answer:
(a) (i) Propanone oxime:

 
(ii) Semicarbazone of CH₃CHO (Ethanal) 

(b) (i) Ethanal to Ethane: 

(ii) Ethanal to 3-hydroxy butanal (Aldol condensation) 

(iii) Ethanal to Ethanol (Partial Reduction)

Question 37. 
(a) Write the chemical equation for the reaction involved in Cannizzaro reaction. 
(b) Draw the structure of the semicarbazone of ethanal. 
(c) Why 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:
(a) Cannizzaro reaction: Aldehydes which do not have an a-hydrogen atom undergo reduction on treatment with conc. alkali and produce alcohol and carboxylic acid salt. 

 
(b) Semicarbazone of CH₃CHO (Ethanal) 

 
(c) In FCH₂-COOH fluorine is more electron withdrawing than chlorine in CICH₂-COOH so FCH₂-COOH is more acidic than CICH₂ - COOH, hence its pka value is lesser than CICH₂-COOH. 

(e) Propanál and Propanone: Propanal being an aldehyde gives positive test with Fehling solution in which a red brown ppt. of cuprous oxide is obtained while propanone being a ketone does not respond to this test. 

Question 38. 
(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:

(b) (i) Benzaldehyde and Acetophenone 
By lodoform test: Acetophenone being a methyl ketone on treatment with I₂ and NaOH (NaO) undergoes iodoform test to give yellow ppt. of iodoform on heating whereas benzaldehyde does not. 
 

(ii) CH₃COOH (Acetic acid) and HCOOH (Formic acid). Formic acid is the only acid which contains aldehydic group and thus show reactions with Tollen's reagent (silver nitrate) and Fehling's solution while Acetic acid does not show. 
Tollen's Test: 
Add ammonical solution of silver nitrate to both the compounds, HCOOH gives silver mirror but CH₃COOH does not. 

(c) CH₃CHO < CH₃CH₂OH < CHCOOH 

Question 39. 
(a) Write the chemical reaction involved in Wolff-Kishner reduction. 
(b) Arrange the following in the increasing order of their reactivity towards nucleophilic reaction: 
C₆H₅COCH₃ CH₃ − CHO,CH₃COCH 
(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 < CH₃ CHO 

(c) The carboxylic carbon is less electrophilic than carbonyl carbon because of the possible resonance structure. 

(e) The given compound has molecular formula C₃H₆O One of its functional isomer i. B shows iodo form test which can be only shown by compounds having methyl Ketone so the compound B will be Acetone or 2-propanone Its functional isomer A will be propanal. 

The formula of compound (A) will be . It will not give iodoform test due to absence of methyl ketone group
 

Question 40. 
(a) Write the product(s) in the following 

(b) Give simple tests to distinguish the following pairs of compounds:
(i) Ethanal and Propanal 
(iii) Benzoic acid and Ethyl benzoate 
(ii) Benzaldehyde and Acetophenone 
Answer:
(a) (i) Aldol condensation: 

(ii) Clemmensen reduction: 

(b) (i) On heating with NaOH and I₂, ethanal forms yellow ppt of CHI₃, whereas propanal can not. 
CH₃CHO + 3I₂ + 4NaOH → CHI₃ + 3NaI + HCOONa + 3H₂O

(ii) On heating with NaOH and I₂, aceptophenone forms yellow ppt of CH₃I, whereas benzaldehyde does not. 
C₆H₅COCH₃ + 3NaOI → C₆H₅COONa + CH₃I ↓+ 2NaOH

(iii) On adding NaHCO₃, benzoic acid produces brisk effervescence of CO₂ gas whereas ethylbenzoate does not. 
C₆H₅COOH + NaHCO₃ → С₆H₅COONa + CO₂↑ + H₂O 

Question 41. 
(a) Give reasons: 
(i) CH₃-CHO is more reactive than CH₃COCH₃ towards HCN. 
(ii) 4-nitrobenzoic acid is more acidic than benzoic acid. 
(b) Describe the following 
(i) Acetylation 
(ii) Cannizzaro reaction 
(iii) Cross aldol condensation 
Answer:
(a) (i) Because carbonyl carbon of CH₃-CHO is more electrophilic than CH₃COCH₃, due to only one electron donating CH-3 group. 
(ii) Because of electron withdrawing nature of -NO₂ group. 

(b) (i) Acetylation : Introduction of an acetyl group/CH₃COO- by heating an organic compound with acetyl chloride/ acetic anhydride. 

(ii) Cannizzaro reaction: Aldehydes having no a-hydrogen atom when treated with conc. NaOH, undergoes self oxidation and self-reduction simultaneously. 

(iii) Cross Aldol Condensation: When aldol condensation is carried out between two different aldehydes or ketones, it is called cross aldol condensation. 

Question 42. 
(a) Complete the following equations: 

(b) Distinguish between: 

Answer:
(a) (i) Cannizzaro reacion: 

(b) (i) On adding NaHCO₃, CH₃COOH produces brisk effervescence of CO₂ gas whereas phenol does not. 
(ii) On heating with Tollen's reagent, CH₃CHO forms silver mirror whereas CH₃COCH, does not. 

Question 43. 
(a) What is meant by the following terms? Give an example of the reaction in each case. 
(i) Aldol 
(ii) Semicarbazone 
(b) Complete the following: 

Answer:
(a) (i) Two molecules of aldehyde and ketones containing a-hydrogen atom react in the presence of aqueous alkali giving product known as Aldol. 
Example: 

(ii) Aldehydes and ketones react with semicarbazide giving product called semicarbazone. 

Question 44. 
Write the product(s) in the following reactions. 

Answer:

Question 45. 
(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:

(b) (i) Tollen's reagent test. Add ammonical solution of silver nitrate (Tollen's Reagent) in both the solutions. Butanal gives silver mirror whereas Butan-2-one does not. Therefore Butanal gives Tollen's test. 

(ii) Ferric chloride test. Add neutral FeCl₃ in both the solutions phenol reacts with neutral FeCl₃ to form an iron- phenol complex giving violet colour but benzoic acid does not. 

Question 46. 
(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:
(a) (i) Etard reaction: 

(ii) Stephen reduction: 

(b) (i) Benzoic acid to Benzaldehyde. Refer to Question 5. (b) (ii). 
(ii) Acetophenone to Benzoic acid: 


(iii) Ethanoic acid to 2-Hydroxyethanoic acid : 

Question 47. 
(a) How will you convert: 
(i) Benzene to acetophenone 
(ii) Propanone to 2-Methylpropan-2-ol 
(b) Give reasons: 
(i) Electrophilic substitution in benzoic acid takes place at meta position. 
(ii) Carboxylic acids are higher boiling liquids than aldehydes, ketones and alcohols of comparable molecular masses. 
(iii) Propanal is more reactive than propanone in nucleophilic addition reactions. 
Answer:
(a) (i) Benzene to acetophenone 

(ii) Propanone to 2-methylpropan-2-ol. 

(b) (i) Because -COOH group is electron withdrawing group and deactivates the benzene ring. As a result of this ortho and para position acquires positive charge but only meta does not so electrophile can attack on metå position. 
(ii) Because -COOH group of carboxylic acids is capable to do intermolecular hydrogen bonding forming a dimer while alcohols, aldehydes and ketones can not. 

(iii) Because of smaller + I effect of one alkyl group in propanal as compared to larger - I effect of 2 alkyl groups of propanone, the magnitude of positive charge on the carbonyl carbon is more in propanal than propanone. 

Question 48.
(a) Write the products of the following reactions 

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

(b) (i) Propanal and Propanone: Propanal gives positive test with Fehling solution in which a red ppt. of cuprous oxide is obtained while propanone does not respond to test. 

(ii) Distinction between Benzaldehyde and Benzoic acid: Benzaldehyde has no alpha hydrogen atom. Therefore, it undergoes Cannizzaro's reaction as follows: 

Where, Benzoic acid dose not undergo Cannizzaro's reaction. 

COMPETITION CORNER:
 
Question 1. 
Which of the following give nucleophilic reaction? 
(a) Kolbe's reaction of phenol 
(b) Williamson's synthesis of ether 
(c) Reimer Tiemann reaction of phenol 
(d) Koble's electrolytic synthesis of ethane from sodium acetate 
(e) Aldol formation from ethanal. 
Answer:
(e) Aldol formation from ethanal. 

Question 2. 
That reaction in which dichlorocarbene act as electrophile: 
(a) Reimer-Tiemann Reaction 
(b) Kolbe's reaction 
(c) Friedal craft alkylation 
(d) Fitting reaction 
Answer:
(a) Reimer-Tiemann Reaction 

Question 3. 
Given Reaction 

(a) Carbylamine reaction 
(b) Hundsdiecker reaction 
(c) Hoffmann reaction 
(d) Etard reaction 
Answer:
(d) Etard reaction 

Question 4.
The product (B) in the following sequence of reaction is
Ethyl benzene 
(a) Benzaldehyde
(b) Benzophenone
(c) Benzoic acid
(d) Acetophenone
Answer:
(c) Benzoic acid

Question 5.
Which one of the following compounds will not give Cannizzaro reaction with base? 
(a) Cl₃CCHO 
(b) Me₃CCHO 
(c) C₆H₅CHO 
(d) HCHO 
Answer:
(a) Cl₃CCHO 

Question 6. 
The reagent used in Etard reaction is: 
(a) Chromyl chloride 
(b) Ethanoyl chloride 
(c) SnCl₂ and HCl
(d) CdCl₂ 
Answer:
(a) Chromyl chloride 

Question 7. 


Answer:

Question 8.
The main product of sequence of reaction is


Answer:

Question 9.
A organic compound X is oxidised by acidified K₂Cr₂O₇ solution. The product formed reacts with phenyl hydrazine but does not give silver mirror test.
(a) 2-Propanol
(b) Ethanal
(c) Ethanol
(d) Propane
Answer:
(a) 2-Propanol

Question 10. 
A Grignard reagent reacts with ketone, the product obtained is:
(a) 1 alcohol
(b) 2 alcohol
(c) 3 alcohol
(d) ethanol
Answer:
(c) 3 alcohol

Question 11.

The product (p) in above reaction is:

Answer:


Question 12.
Which of the following is nucleophilic addition reaction?

Answer:


Question 13.
Tollen reagent is:
(a) Alkaline solution of copper nitrate
(b) Ammonical silver nitrate
(c) Ammonical copper nitrate
(d) None of these
Answer:
(b) Ammonical silver nitrate

Question 14.

The correct structure of product A In reaction is:

Answer:


Question 15.
The correct order of acidity is:

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

Question 16.
The best representation of carboxylate ion structure is:

Answer: