Lactic acid occurs naturally, for example in sour milk.
What is a property of lactic acid?
It decolourises aqueous bromine rapidly.
It is insoluble in water.
It reduces Fehling’s reagent.
It reacts with sodium carbonate.
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First teaching 2023
First exams 2025
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21.1 Organic Synthesis
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21.1 Organic Synthesis
Lactic acid occurs naturally, for example in sour milk.
What is a property of lactic acid?
It decolourises aqueous bromine rapidly.
It is insoluble in water.
It reduces Fehling’s reagent.
It reacts with sodium carbonate.
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Which reagent can be used to convert CH3CH2CO2CH3 into CH3CH2CO2CH2Cl?
Chlorine in bright sunlight at 100 °C
Concentrated hydrochloric acid at 100 °C
Phosphorus pentachloride at room temperature
Sulphur dichloride oxide (thionyl chloride, SOCl2) at 50 °C
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Which reactions produce a coloured organic compound?
|
1 |
Ethene + cold dilute acidified potassium manganate (VII) |
|
2 |
Ethanol + acidified potassium dichromate (VI) |
|
3 |
Ethanal + 2,4-dinitrophenylhydrazine reagent |
1 only
1 and 2
3 only
2 and 3
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A compound C has the following properties:
What could C be?
Propene
Propanol
Propanoic acid
Propyl propanoate
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Tartaric acid can occur naturally, for example in wine, and may be synthesised in the laboratory.
The laboratory synthesis occurs in 2 steps:
OHCCHO intermediate HO2CCH(OH)CH(OH)CO2H
tartaric acid
Which reagents could be used for this synthesis?
Step 1 |
Step 2 |
|
A B C D |
HCl (aq) H2SO4 (aq) KCN (aq/alcoholic) HCN, NaCN (aq/alcoholic) |
HCN (g) K2Cr2O7 / H2SO4 (aq) K2Cr2O7 / H2SO4 (aq) H2SO4 (aq) |
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This molecule is responsible for the flavour of spearmint chewing gum.
What is a true statement about the functional groups 1 or 2?
1 will undergo nucleophilic addition
1 will undergo electrophilic substitution
2 will undergo nucleophilic addition
2 will undergo electrophilic substitution
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Sorbic acid is a natural organic compound which is used as a food preservative because it kills fungi. Sorbic acid reacts with bromine in an organic solvent and hydrogen in the presence of a nickel catalyst.
How many moles of bromine (in an organic solvent) and of hydrogen (in the presence of a Pt / Ni catalyst) will be incorporated into one mole of sorbic acid by these reactions?
Moles of bromine |
Moles of hydrogen |
|
A B C D |
2 2 2 2 |
2 3 2 3 |
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The naturally-occurring molecule civetone was one of the first know ingredients used in perfumery.
Which reagent will not react with civetone?
Fehling’s reagent
Hydrogen bromide
2,4-dinitrophenylhydrazine reagent
Sodium tetrahydridoborate (III), NaBH4
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An alkene is reacted with acidified manganate (VII) ions, MnO4- . The organic product has a relative molecular mass greater than that of the alkene by 34.
What are the specific conditions for this reaction?
Cold, dilute MnO4-
Cold, concentrated MnO4-
Hot, dilute MnO4-
Hot, concentrated MnO4-
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Pentanoic acid can be produced from 1-bromobutane using reagents Y and Z as shown below.
1-bromobutane compound X pentanoic acid
What could be reagents Y and Z?
Y |
Z |
|
A B C D |
NaOH (aq) NH3 in ethanol KCN in ethanol KCN in ethanol |
HCl (aq) H+ /Cr2O72- (aq) HCl (aq) NaOH (aq) |
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In which reaction has a carbocation intermediate?
CH3CH2Br + NaOH CH3CH2OH + NaBr
CH2=CH2 + Br2 CH2BrCH2Br
CH3CH3 + Cl2 CH3CH2Cl + HCl
CH3CHO + HCN CH3CH(OH)CN
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Hept-4-enal naturally occurs in cow’s milk.
CH3CH2CH=CHCH2CH2CHO
hept-4-enal
What organic product is formed when hept-4-enal is reduced with either hydrogen with a nickel catalyst or sodium borohydride?
CH3(CH2)5CH3 when hept-4-enal is reduced by H2 / Ni
CH3(CH2)5CHO when hept-4-enal is reduced by NaBH4
CH3CH2(CH)2(CH2)3OH when hept-4-enal is reduced by H2 / Ni
CH3CH2(CH)2(CH2)3OH when hept-4-enal is reduced by NaBH4
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The diagram shows the structure of the naturally-occurring molecule cholesterol.
Two separate test tubes of cholesterol are used in an experiment. One test tube of cholesterol is treated with cold, dilute acidified KMnO4, and the other is treated with hot, concentrated acidified KMnO4.
Which row correctly describes the change in the number of chiral carbon atoms in the molecule during each reaction and the structure of the product in each test tube?
Cold, dilute acidified KMnO4 |
Hot, concentrated acidified KMnO4 |
|||
Change in the number of chiral carbons |
Number of hydroxy groups in product |
Change in the number of chiral carbons |
Number of 6-membered rings remaining in product |
|
A B C D |
+1 +1 +2 +2 |
1 1 3 3 |
0 -1 -1 0 |
2 3 2 3 |
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The cyclic compound G is heated with dilute hydrochloric acid.
What are the products of the reaction?
HOCH2CO2H and H2NCH2CO2H
H2NCOCH2OH and HOCH2CHO
HOCH2CONH3+ and HOCH2CHO
HO2CCH2NH3+ and HO2CCH2OH
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Santonin is a drug that has been used to treat a worm infection.
When santonin is first treated with warm dilute H2SO4, product X is formed. If X is treated with cold acidified KMnO4, the final product Y is obtained.
How many atoms of hydrogen in each molecule of product Y could be displaced in a reaction with sodium metal?
2
4
5
6
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Compound M is used in leather processing.
Compound M is synthesised in the presence of concentrated sulfuric acid and heat.
Which other starting material(s) are required to synthesise compound M?
CH3COOH only
HOCH2COOH only
CH3COOCH2COOH only
CH3COOH mixed with HOCH2COOH
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Mixture F is produced upon refluxing compound G with aqueous sodium hydroxide.
Upon distillation with acidified potassium dichromate (VI) propanone is produced. Mixing J with aqueous silver nitrate and dilute nitric acid gives a cream precipitate.
What could compound G be?
CH3CHICH3
CH3CHBrCH3
CH3CH2CH2I
CH3CH2CH2Br
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Antipyrine is a drug used to reduce fever. The initial step of its synthesis is the reaction of phenylhydrazine with compound X.
What is the product Y?
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Ibuprofen is an anti-inflammatory drug, the structure of which is shown below.
Which reaction leads to the formation of ibuprofen?
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