11 mark
What is formed when butanone is refluxed with a solution of NaBH4?
Butane
Butan-1-ol
Butan-2-ol
Butanal
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Syllabus Edition
First teaching 2020
Last exams 2024
|
3.5 Carbonyl Compounds
21 mark
In 1903 Arthur Lapworth became the first chemist to investigate a reaction mechanism. The reaction of hydrogen cyanide with propanone.
What do we now call the mechanism of this reaction?
Nucleophilic substitution
Nucleophilic addition
Electrophilic substitution
Electrophilic addition
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31 mark
Which carbonyl compound(s) react with both LiAlH4 and Tollens’ reagent?
Ketones only
Aldehydes only
Both aldehydes and ketones
Neither aldehydes nor ketones
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41 mark
In a nucleophilic addition reaction, aqueous methanolic solution of NaBH4 acts as a reducing agent when added to propanal, CH3CH2CHO.
What is the first step of this mechanism?
Attack of an H– ion at the oxygen atom of the carbonyl group.
Attack of an H+ ion at the oxygen atom of the carbonyl group.
Attack of an H– ion at the carbon atom of the carbonyl group.
Attack of an H+ ion at the carbon atom of the carbonyl group.
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51 mark
The characteristic smell of burnt sugar is partly caused by the following compound.
There are two functional groups in the compound.
Which reagent will react with both functional groups?
Sodium hydroxide
Hydrogen cyanide
Fehling’s solution
Acidified potassium dichromate (VI)
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61 mark
In which reaction is the organic compound oxidised?
CH3CH2CN + dilute H2SO4
CH3CH2CHO + Tollens’ reagent
CH3COCH2CH3 + 2,4-dinitrophenylhydrazine reagent
CH3CH2CH2OH + concentrated H3PO4
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71 mark
Ethanal, CH3CHO, is reduced using NaBH4 in aqueous ethanol in a nucleophilic addition reaction.
What is the first step of this mechanism?
The oxygen atom of the carbonyl group is attacked by an H– ion
The oxygen atom of the carbonyl group is attacked by an H+ ion
The carbon atom of the carbonyl group is attacked by an H– ion
The carbon atom of the carbonyl group is attacked by an H+ ion
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81 mark
The compounds below are treated with hydrogen cyanide.
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1 |
Butanal |
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2 |
Pentan-3-one |
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3 |
2-chlorobutane |
Which compounds react and produce a molecule containing a chiral centre?
1 only
1 and 2
2 only
2 and 3
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91 mark
The orange colour of carrots is due to the presence of β-carotene, the structure of which is shown in the diagram below.
Hot, concentrated, acidified KMnO4 will oxidise β-carotene.
When an individual molecule of β-carotene is oxidised in this way there are multiple possible products.
How many of these product molecules contain a ketone functional group?
3
6
9
12
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101 mark
Hex-3-enal is used as a flavouring agent.
CH3CH2CH=CHCH2CHO
hex-3-enal
Which row correctly shows the product formed when hex-3-enal is treated with the given reducing agent?
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Product |
Reducing agent |
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A B C D |
CH3(CH2)4CH3 CH3(CH2)4CH2OH CH3(CH2)4CHO CH3(CH2)4CHO |
H2 + Ni NaBH4 H2 + Ni NaBH4 |
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11 mark
When HCN reacts with butanal, CH3CH2CH2CHO, product X is formed. If X is then hydrolysed by aqueous acid, product Y is produced.
When pentanal, C4H9CHO, is heated under reflux with acidified potassium dichromate (VI), product Z is formed.
What is the difference in relative molecular mass of products Y and Z?
12
14
16
18
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21 mark
Cyanohydrins (also called hydroxynitriles) can be made from carbonyl compounds by generating CN– ions from HCN in the presence of a weak base.
In a similar reaction, –CH2CO2CH3 ions are generated from CH3CO2CH3 by strong bases.
Which compound can be made from an aldehyde and CH3CO2CH3 in the presence of a strong base?
CH3CH(OH)CO2CH3
CH3CO2CH2CH(OH)CH3
CH3CH2CH(OH)CH2CO2CH3
(CH3)2C(OH)CH2CO2CH3
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31 mark
When compound T reacts with its own oxidation product, a sweet-smelling liquid is produced.
What is the identity of compound T?
Butanal
Butanone
Butan–1–ol
Butanoic acid
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41 mark
Three separate test tubes, 1, 2 and 3, each contain 1 mol of compound X.
An excess of sodium borohydride is added to test tube 1 and an excess of acidified sodium permanganate is added to test tube 2. No reagent is added to test tube 3.
Following this, 2 mol of HCN (g) is added to each test tube and the HCN completely reacts in all 3.
What could X be?
CH3COCH2CH2CHO
CH3CH(OH)COCH3
H2C=CHCH2CHO
HOCH3CH2CH2CHO
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51 mark
Glyceraldehyde, HOCH2CH(OH)CHO, is formed during photosynthesis on the pathway to glucose production.
Which reagents produce an organic product without a chiral carbon atom when reacted with glyceraldehyde?
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1 |
Warmed acidified K2Cr2O7 |
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2 |
Fehling’s reagent |
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3 |
NaBH4 |
1, 2 and 3
1 and 3
2 and 3
1 only
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61 mark
Which of the following techniques will increase the rate of reaction between ethanal and aqueous hydrogen cyanide?
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1 |
Increasing the temperature. |
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2 |
Performing the reacting under ultraviolet light. |
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3 |
Adding a small quantity of aqueous sodium cyanide. |
1 only
1 and 3
2 and 3
1, 2 and 3
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71 mark
Hydrocarbons 1, 2 and 3 all occur naturally.
All three are treated with hot acidified potassium manganate (VII) separately.
Which of the hydrocarbons 1, 2 and 3 will be split into two organic compounds, both containing a ketone group?
1 only
1 and 2
2 only
1 and 3
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81 mark
Which carbonyl compounds can be easily oxidised to carboxylic acids that are readily soluble in water?
1 only
1 and 2
2 and 3
3 only
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91 mark
The hormone progesterone is produced during pregnancy to suppress ovulation.
Which reagents would give positive results with this compound?
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1 |
Fehling’s reagent |
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2 |
Aqueous bromine |
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3 |
2,4-dinitrophenylhydrazine |
1, 2 and 3
1 and 2
2 and 3
1 only
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101 mark
The Mr of compound X is 72.
The composition by mass of X is 66.7 % carbon, 11.1 % hydrogen and 22.2 % oxygen.
X does not react with Fehling’s reagent and gives an orange precipitate with 2,4-dinitrophenylhydrazine reagent.
What can be deduced from this information?
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1 |
X is a ketone |
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2 |
X is butanone |
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3 |
X is a carbonyl compound |
1 and 2
1, 2 and 3
3 only
1 only
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11 mark
CH3COCH2CHO CH3COCH2CH2OH CH3CH2CH2CHO CH3CH(OH)CH2CH3
1 2 3 4
Which of these compounds gives a positive response to Tollens’ reagent and can also be oxidised by acidified dichromate (VI) solution?
1 and 2
1 and 3
2 and 3
3 and 4
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21 mark
When alkaline I2 solution is added to butanone, a yellow precipitate is formed.
Which of the following compounds is responsible for the precipitate?
CH3CH2COCH2I
CH3CH2CO2-
CH3CHICOCH3
CHI3
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31 mark
Liquid L is known to be either a single organic compound or a mixture of organic compounds.
Two tests were done on liquid L to determine its constituents:
- When treated with sodium, L gives off hydrogen gas.
- When treated with 2,4-dinitrophenylhydrazine reagent, L gives orange crystals.
Which deductions about L can definitely be made?
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1 |
At least one component of L is an alcohol. |
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2 |
At least one component of L is a carbonyl compound. |
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3 |
Only one of the components of L is a carbonyl compound. |
1, 2 and 3
1 and 2
2 and 3
2 only
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41 mark
The colour of warm acidified sodium dichromate (VI) changes from orange to green when added to compound Y. 1 mol of Y reacts with 2 mol of hydrogen cyanide in the presence of potassium cyanide.
What could Y be?
H2C=CHCH2CHO
CH3CH2CH2CHO
OHCCH2CH2CHO
CH3COCH2COCH3
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51 mark
Hydroxyethanal has the structural formula HOCH2CHO.
In an experiment hydroxyethanal is heated under reflux with an excess of acidified potassium dichromate (VI) until no further oxidation takes place.
What is the skeletal formula of the organic product formed in the experiment?
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61 mark
Which reagent will give similar results with both propanone and propanal?
2,4-dinitrophenylhydrazine reagent
Acidified aqueous potassium dichromate (VI)
An aqueous solution containing [Ag(NH3)2]+ (Tollens’ reagent)
An alkaline solution containing complexed Cu2+ ions (Fehling’s solution)
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71 mark
Carvone is used as a flavouring for spearmint chewing gum.
When carvone is heated for a prolonged time with hot concentrated acidified potassium manganate (VII) the products carbon dioxide and compound X are formed.
X contains nine carbon atoms and reacts with 2,4-dinitrophenylhydrazine reagent.
What is the maximum number of molecules of 2,4-dinitrophenylhydrazine that will react with one molecule of X?
4
3
2
1
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81 mark
When ethanal and propanone are reacted separately with reagent X both cause the same colour change.
Which colour changes occurs in both reactions?
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1 |
Black to yellow |
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2 |
Orange to green |
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3 |
Blue to red |
1 only
1 and 2
2 and 3
1, 2 and 3
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91 mark
A reaction occurs between ethanal and hydrogen cyanide in the presence of sodium cyanide.
Which statements about the reaction mechanism are correct?
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1 |
The last stage involves the formation of a hydrogen-oxygen bond. |
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2 |
In the intermediate, the oxygen carries a negative charge. |
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3 |
A new carbon-carbon bond is formed. |
1 only
1 and 2
2 and 3
1, 2 and 3
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101 mark
When compounds 1, 2 and 3 react with PCl5, hydrogen chloride is evolved. However, only one of the three reacts with 2,4-dinitrophenylhydrazine reagent.
Which one of the following combinations could be 1, 2 and 3?
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