Aldehydes And Ketones Test

Result

Aldehydes And Ketones Test - 4

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Weekly Quiz Competition

Question 1
1 / -0

What is the increasing order of the rates of HCN addition to compounds A to D?

A. HCHO
B. CH₃COCH₃
C. PhCOCH₃
D. PhCOPh

A
C < D < B < A

B
A < B < C < D

C
D < B < C < A

D
D < C < B < A

Solution

The greater the positivity of carbon in carbonyl group, the higher the reactivity towards nucleophilic addition, i.e. HCN addition.
Aldehydes are more reactive than ketones. The bulkier the alkyl group of the ketone, the more hindered is the nucleophilic attack on the carbonyl carbon. Hence, the correct order is D < C < B < A.
Question 2
1 / -0

Which of the following aldehydes is most reactive towards nucleophilic addition reactions?

A
HCHO

B
CH₃CHO

C
C₂H₅CHO

D
PhCHO

Solution

Formaldehyde (HCHO) is the most reactive aldehyde towards nucleophilic addition reactions because of the absence of the +I effect.
Question 3
1 / -0

Cannizzaro reaction is not given by

A
trimethylacetaldehyde

B
acetaldehyde

C
benzaldehyde

D
formaldehyde

Solution

For aldehydes with alpha hydrogen atom to the carbonyl, i.e. R₂CHCHO, the preferred reaction is an aldol condensation, originating from deprotonation of this hydrogen. This reaction restricts the scope of Cannizzaro reaction.
Question 4
1 / -0

Benzyl alcohol is obtained from benzaldehyde by which of the following reactions?

A
Wurtz reaction

B
Cannizzaro reaction

C
Claisen reaction

D
Perkin reaction

Solution

Aldehydes that do not have alpha hydrogen undergo Cannizzaro reaction. So benzaldehyde, which does not have alpha hydrogen, undergoes this reaction to form benzyl alcohol.