Aldehydes And Ketones Test

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Aldehydes And Ketones Test - 9

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Weekly Quiz Competition

Question 1
1 / -0

Methanal and ethanal are miscible in water in all proportions because

A
the dipole-dipole interactions are strong

B
they have a low molecular mass

C
they form hydrogen bonds with water

D
they ionise in water

Solution

The lower members of aldehydes and ketones are soluble in water because of the formation of hydrogen bonds.
Question 2
1 / -0

Propanone and propanal are functional isomers and have the same molecular formula C₃H₆O and molecular mass. Which of the two isomers has higher boiling point?

A
Propanal

B
Propanone

C
Nothing can be predicted

D
Both have the same boiling point

Solution

Aldehydes have a higher boiling point than isomeric ketones because of H-bonding.
Question 3
1 / -0

Which of the following statements is incorrect about the reactivity of aldehydes and ketones towards nucleophilic addition?

A
It is greater in aldehydes because of lesser steric hindrance to the attacking nucleophile.

B
It is greater in ketones because of the +I effect of the alkyl groups.

C
It is greater in aldehydes because of greater electrophilicity of the carbonyl carbon.

D
Carbonyl compounds have a tendency to show nucleophilic additions because of the polarity of the C = O bond.

Solution

Ketones are less reactive towards nucleophilic addition because the +I effect of the alkyl groups increases the electron density around the carbonyl carbon and decreases its electrophilicity.
Question 4
1 / -0

Identify the correct order of reactivity towards nucleophilic addition reactions.

A
Ar₂C=O < R₂C=O < ArCHO < RCHO < H₂C=O

B
H₂C=O < R₂C=O < ArCHO < RCHO < Ar₂C=O

C
Ar₂C=O < RCHO < ArCHO < R₂C=O < H₂C=O

D
Ar₂C=O < R₂C=O < RCHO < ArCHO < H₂C=O

Solution

Aldehydes are more reactive towards nucleophilic addition than ketones. Among the aldehydes, formaldehyde is the most reactive.
Question 5
1 / -0

Which of the following reagents can be used to separate a mixture of CH₃CH₂OH and CH₃CHO?

A
NH₂OH

B
NaHSO₃

C
NH₂NH₂

D
HCN

Solution

Aldehydes react with NaHSO₃ to form bisulphite adducts, which are white crystalline solids and are insoluble in water. They can be regenerated by acidic or alkaline hydrolysis.
Question 6
1 / -0

The compound that reacts differently with C₆H₅CHO, HCHO and CH₃CHO is

A
NH₂OH

B
NH₂NH₂

C
NH₃

D
H₂NNHCONH₂

Solution

2NH₃ +3C₆H₅CHO → (C₆H₅CH = N)₂CHC₆H₅+ 3H₂O
6HCHO + 4 NH₃→(CH₂)₆N₄ + 6H₂O
CH₃CHO + NH₃→CH₃CH = NH

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Re-Attempt Weekly Quiz Competition

Aldehydes And Ketones Test - 9

Result

Aldehydes And Ketones Test - 9

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SHARING IS CARING

Question 1

the dipole-dipole interactions are strong

they have a low molecular mass

they form hydrogen bonds with water

they ionise in water

Solution

Question 2

Propanal

Propanone

Nothing can be predicted

Both have the same boiling point

Solution

Question 3

It is greater in aldehydes because of lesser steric hindrance to the attacking nucleophile.

It is greater in ketones because of the +I effect of the alkyl groups.

It is greater in aldehydes because of greater electrophilicity of the carbonyl carbon.

Carbonyl compounds have a tendency to show nucleophilic additions because of the polarity of the C = O bond.

Solution

Question 4

Ar2C=O < R2C=O < ArCHO < RCHO < H2C=O

H2C=O < R2C=O < ArCHO < RCHO < Ar2C=O

Ar2C=O < RCHO < ArCHO < R2C=O < H2C=O

Ar2C=O < R2C=O < RCHO < ArCHO < H2C=O

Solution

Question 5

NH2OH

NaHSO3

NH2NH2

HCN

Solution

Question 6

NH2OH

NH2NH2

NH3

H2NNHCONH2

Solution

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Ar₂C=O < R₂C=O < ArCHO < RCHO < H₂C=O

H₂C=O < R₂C=O < ArCHO < RCHO < Ar₂C=O

Ar₂C=O < RCHO < ArCHO < R₂C=O < H₂C=O

Ar₂C=O < R₂C=O < RCHO < ArCHO < H₂C=O

NH₂OH

NaHSO₃

NH₂NH₂

NH₂OH

NH₂NH₂

NH₃

H₂NNHCONH₂