Aldehydes And Ketones Test

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Aldehydes And Ketones Test - 15

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Question 1
1 / -0

Vanillin, used as a flavouring agent is-

A
An Aliphatic alcohol

B
An Aromatic aldehyde

C
A Hydrocarbon

D
A Carbohydrate

Solution

Hint: Parent chain contains benzaldeyde

The structure of vanillin is as follows:

4-hydroxy-3-methoxy benzaldehyde
Question 2
1 / -0

The correct statement regarding a carbonyl compound with a hydrogen atom on its alpha-carbon, is-

A
A carbonyl compound with a hydrogen atom on its alpha-carbon rapidly equilibrates with its corresponding enol and this process is known as aldehyde-ketone equilibration.

B
A carbonyl compound with a hydrogen atom on its alpha-carbon rapidly equilibrates with its corresponding enol and this process is known as carbonylation.

C
A carbonyl compound with a hydrogen atom on its alpha-carbon rapidly equilibrates with its corresponding enol and this process is known as keto-enol tautomerism.

D
A carbonyl compound with a hydrogen atom on its alpha-carbon never equilibrates with its corresponding enol.

Solution

Hint: Enol form contains a double bond and an OH group.

When a carbonyl compound with a hydrogen atom on its alpha-carbon rapidly equilibrates with its corresponding enol component,it is called keto-enol tautomerism.
Question 3
1 / -0

The major product formed when cyclohexanecarbaldehyde reacts with PhMgBr and H₃O⁺ is-

A

B

C

D
None of the above

Solution

Hint: Nucleophilic addition on the carbonyl carbon of aldehyde followed by acidic neutralization

Explanation:

Step 1: Do the nucleophilic addition of Grignard reagent nucleophile on the carbonyl carbon of aldehyde to form anion

Step 2:

Do the acidic neutralization of oxygen-magnesium salt with H3O+ to give secondary alcohol product.
Question 4
1 / -0

The correct order of decreasing acid strength of

trichloroacetic acid (A), trifluoroacetic acid (B),

acetic acid (C) and formic acid (D) is-

A
B > A > D > C

B
B > D > C > A

C
A > B > C > D

D
A > C > B >D

Solution

Hint: Stability of conjugate base is directly proportional to acidity of acid

As stability of conjugate base increases the acidity of acid increases. The structures of conjugate bases is as follows:

As number of electronegative elements at alpha position increases the stability of conjugate base increases due to -I effect. Fluorine is more electronegative than chlorine. Hence, a is more stable than b. In d, +I effect of CH₃ destabilized the negative charge hence, c is more stable than d. The stability order of conjugate base is a > b > c >d.

Hence, the correct order of decreasing acid strength of hgiven acids are B > A > D > C.

The order of acidity of given compounds is
Question 5
1 / -0

A compound that can be reduced to the corresponding hydrocarbon by Zn-Hg/ conc HCl is -

A
Butan-2-one

B
Acetic acid

C
Acetamide

D
Ethyl acetate

Solution

Hint: Reduction of ketone to the corresponding alkane using Zn/HCl

When ketone reacts with Zn-Hg/ conc HCl then it converts into an alkane. The reaction is an example of Clemmensen's reaction.
Question 6
1 / -0

The correct sequence of increasing order of reactivity in nucleophilic addition reactions is -

A
Butanone < Propanone < Propanal < Ethanal

B
Butanone > Propanone > Propanal > Ethanal

C
Butanone < Propanal< Propanone < Ethanal

D
Propanal< Propanone < Ethanal < Butanone

Solution

Hint: Rate of nucleophilic addition reaction based on electronic effects

Explanation:

Nucelophilic attack need:

1) High δ+ charge density arounc C = 0

2) Lesser steric hindrance
Question 7
1 / -0

The most reactive compound among the following towards nucleophilic addition reaction is-

A
Benzaldehyde

B
p-Tolualdehyde

C
p-Nitrobenzaldehyde

D
Acetophenone

Solution

Hint: Apply the concept of nucleophilic addition in carbonyl compounds

The structure of the given compounds are as follows:

If benzaldehyde is attached to an electron-withdrawing group then the reactivity of benzaldehyde increases. If benzaldehyde is attached to an electron-donating group then the reactivity of benzaldehyde decreases.
Question 8
1 / -0

A compounds with molecular formula C₅H₁₀ yields acetone on ozonolysis is -

A
2-Methyl-2-butene

B
2-Methyl-1-butene

C
Cyclopentane

D
3-Methyl-1-butene

Solution

Hint: Alkene reacts with O₃ in ozonolysis.

The ozonolysis of the given compounds are as follows:

Only 2-methyl-2-butene yields acetone on ozonolysis. Cyclopantane didnot give ozonolysis reaction.
Question 9
1 / -0

2-Methyl propene gives on oxidation with hot KMnO₄ gives-

A
Acetone

B
Ethanoic acid

C
CO₂ and H₂O

D
Both 1 & 3

Solution

Hint: One of the products is carbon dioxide

Explanation:

It is an example of an oxidation reaction. The terminal carbon is converted into carbon dioxide and the other part of the compound is oxidized into ketone. The reaction is as follows:
Question 10
1 / -0

The IUPAC name of CH₃COCH₂COCH₃ is-

A
Pentane-2,4-dione

B
Pentane-1,4-dione

C
Pentane-2,2-dione

D
Pentane-3,4-dione

Solution

Hint: Functional group is a ketone, and it is attached at the 2nd, and 4th carbon.

Explanation:

Follow the IUPAC rules for the ketone functional group where +one is used as a suffix with the longest chain is having 5 carbon

Hence the IUPAC name is Pentane-2,4-dione