Aldehydes And Ketones Test

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Aldehydes And Ketones Test - 18

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Question 1
1 / -0

The IUPAC name of PhCOPh is-

A
Diphenylmethanone

B
Benzophenone

C
Dibenzylmethanone

D
Dibenzylketone

Solution

Hint: Ketone is the functional group and benzene ring will be substituents

Explanation:

"one" is used as a suffix, and when more than one ring is attached, rings become substituents.

Hence the IUPAC name is Diphenylmethanone.

Question 2

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Match the common names given in Column I with the IUPAC names given in Column II.

Column l (Common names)	Column ll (IUPAC names)
A. Cinnamaldehyde	1. Pentanal
B. Acetophenone	2. Prop-2-enal
C. Valeraldehyde	3. 1-phenylethanone
D. Acrolein	4. 3-Phenylprop-2-en-al

Codes

A B C D

2 3 4 1

3 1 4 2

1 4 3 2

4 3 1 2

Solution

Hint: Valeraldehyde is Pentanal.

Common names	Structure	IUPAC names
A. Cinnamaldehyde		3-Phenylprop-2-en-al
B. Acetophenone		1-Phenylethanone
C. Valeraldehyde		Pentanal
D. Acrolein		Prop-2-en-al

Question 3

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Match the reactions given in Column I with the suitable reagents given in Column II.

Column l (Reactions)	Column ll (Reagents)
A. Benzophenone→Diphenylmethane	1. LiAlH₄
B. Benzaldehyde→ 1-Phenylethanol	2. DlBAL-H
C. Cyclohexanone →Cyclohexanol	3. Zn(Hg)/Conc.HCl
D. Phenyl benzoate → Benzaldehyde	4.CH₃MgBr

Codes

A B C D

2 3 4 1

3 4 1 2

1 4 3 2

4 3 2 1

Solution

Reactions	Reagents
A.	Zn(Hg)/Conc. HCl
B.	CH₃MgBr
C.	LiAlH₄
D.	DlBAL-H

Question 4
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A: Aldehydes are more reactive than ketones in nucleophilic addition reactions.

R: The magnitude of positive charge present on the carbonyl carbon of aldehydes is more than that of ketones.

A
Both Assertion & Reason are true and the reason is the correct explanation of the assertion.

B
Both Assertion & Reason are true but the reason is not the correct explanation of the assertion.

C
Assertion is a true statement but Reason is false.

D
Both Assertion and Reason are false statements.

Solution

Hint: Aldehydes are more reactive than ketones in nucleophilic addition reactions.

Aldehydes are generally more reactive than ketones in nucleophilic addition reactions due to steric and electronic reasons. Sterically, the presence of two relatively large substituents in ketones hinders the approach of nucleophiles to carbonyl carbon than in aldehydes having only one such substituent.

Electronically, aldehydes are more reactive than ketones because two alkyl groups in ketone reduce the electrophilicity of the carbonyl carbon more effectively than in the aldehyde.
Question 5
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The correct increasing order of boiling point is-

A
CH₃OCH₃ < CH₃CHO < CH₃CH₂OH < CH₃COOH

B
CH₃CHO < CH₃OCH₃ < CH₃CH₂OH < CH₃COOH

C
CH₃CHO < CH₃OCH₃ < CH₃COOH < CH₃CH₂OH

D
CH₃OCH₃ < CH₃CH₂OH < CH₂CHO < CH₃COOH

Solution

Hint: Order of intermolecular forces is Hydrogen bonding > dipole-dipole > london forces

Explanation:

The boiling point depends on intermolecular forces between molecules. In alcohol, hydrogen bonding takes place.

Thus, alcohols tend to have a higher boiling point than aldehyde because in aldehyde dipole-dipole interaction occurs. Dipole-dipole interaction is less than hydrogen bonding.

The same reason supports the fact that carboxylic acids have even higher boiling points than aldehyde and alcohol.

In carboxylic acid, strong hydrogen bonding occurs than alcohol. Thus, the carboxylic acid boiling point is maximum.

Ether has a minimum boiling point because it has very weak dipole-dipole interactions.
Question 6
1 / -0

The product formed by the reaction of an aldehyde with a primary amine is-

A
Ketone

B
Carboxylic acid

C
Aromatic acid

D
Schiff base

Solution

Hint: Nucleophilic addition reaction

When ammonia and derivative of ammonia reacts with aldehyde or ketone then nucleophilic addition reaction takes place.

So, when primary amine reacts with aldehyde then schiff base is formed as a product. The reaction is as follows:

The mechanism of the reaction is as follows:
Question 7
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Acetone on reaction with concentrated H₂SO₄ gives-

A
Phorone

B
Mesitylene

C
Mesityl oxide

D
Crotonaldehyde

Solution

Hint: Prouct is 1,3,5-Trimethylbenzene

Explanation

Mesitylene is obtained either by treating 3 molecules of acetone with conc. H₂SO₄ or passing propyne through a red-hot tube. Mesitylene is a condensation product as it is formed by the removal of water molecules.
Question 8
1 / -0

A carbonyl compound reacts with hydrogen cyanide to form cyanohydrins, that forms a racemic mixture of α-hydroxy acid on hydrolysis. The carbonyl compound is-

A
Acetaldehyde

B
Acetone

C
Diethyl ketone

D
Formaldehyde

Solution

Hint: Racemic mixture is obtained when molecule contains chiral carbon

Cyanohydrins are formed and hydrolysed according to the mechanism shown below:

Since it is given that a racemic mixture of hydroxyacid is formed, hence asymmetric or chiral carbon atom must be present in hydroxyacid. From the following reactions shown below, it can be seen that only hydroxyacid obtained from acetaldehyde is chiral and will lead to the formation of the racemic mixture of two hydroxyacids.
Question 9
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The product formed in aldol condensation is-

A
A beta-hydroxy acid

B
A beta-hydroxy aldehyde or a beta-hydroxy ketone

C
An alpha-hydroxy aldehyde or ketone.

D
An alpha-beta unsaturated ester

Solution

Hint: Aldol contains both aldehyde and OH group.

In the aldol condensation, two aldehyde molecules or ketones molecule reacts with each other in the presence of base and beta-hydroxyaldehyde or beta-hydroxyketone is formed as a product. In the next, beta-hydroxyaldehyde or beta-hydroxyketone heated and alpha-betaunsaturated aldehyde or ketone is obtained as a product.

The reaction is as follows:
Question 10
1 / -0

Self-condensation of two moles of ethyl acetate in presence of sodium ethoxide yield-

A
Ethyl butyrate

B
Acetoacetic ester

C
Methyl acetoacetate

D
Ethyl propionate

Solution

Hint: Claisen condensation reaction

When two moles of ethyl acetate in the presence of sodium ethoxide reacts with each other then Claisen condensation reaction occur and an acetoacetic ester is obtained as a product.

The reaction is as follows: