Introduction to organic chemistry — AS & A Level Chemistry (9701) questions by topic
Chirality and rate-equation reasoning both appear in this topic: counting chiral carbon atoms in a drug structure such as perindopril, deducing optical isomer counts, and constructing a rate equation from steps consistent with given reaction orders.
Identify, draw, deduce, state and calculate top the command words across 53 questions from 2023 to 2025 papers, worth from 1 to 15 marks, mixing structural counting with mechanism steps that must balance exactly. Checking each mechanism step or rate-equation answer with instant marking flags a squared ClO2 concentration or an unbalanced step before the same slip appears in the next multi-step organic question.
What examiners look for
- A recurring criticism is a mechanism step not being a 1:1 molar ratio consistent with the given orders of reaction, or steps that were not balanced overall.
- A common error was squaring the concentration of ClO2 where the rate equation did not require it.
- Examiners note candidates gave 'carbonyl' and 'arene' as common wrong answers, and 'tetrahedral' where few understood what 'geometry' was actually asking for.
- Strong answers suggested two mechanism steps consistent with the given orders that summed to the overall equation, and gave the correct rate equation as a result.
- Candidates who plotted points accurately and drew a suitable best-fit curve tended to answer this topic's data questions well.
May–June 2025, Paper 11
An organic compound J reacts with an excess of sodium to produce an organic ion with a charge of –3. J reacts with an excess of NaOH(aq) to produce an organic ion with a charge of…
Answer this question and get it marked →Structural isomerism and stereoisomerism should be considered when answering this question. 2,5-dibromohexane is heated under reflux with ethanolic KOH. How many isomeric…
Answer this question and get it marked →A possible mechanism for the exothermic hydrolysis of 2-chloro-2-methylpropane is shown. Step 1 (slow): (CH3)3CCl → (CH3)3C^+ + Cl^- Step 2 (fast): (CH3)3C^+ + OH^- → (CH3)3COH…
Answer this question and get it marked →The structure of the testosterone molecule is shown, with C1 (the carbon bearing the ketone C=O) and C2 (the carbon bearing the OH group) labelled. Which statements are correct? 1…
Answer this question and get it marked →The structural formula of hept-1,4,5-triene is shown. CH2=CHCH2CH=CCHCH3 How many of the carbon atoms in one molecule of hept-1,4,5-triene are sp^2 hybridised? A 4 B 5 C 6 D 7
Answer this question and get it marked →May–June 2025, Paper 12
Including structural isomers and stereoisomers, how many isomers are there of C2H2Br2? A 2 B 3 C 4 D 5
Answer this question and get it marked →Which compound exhibits stereoisomerism? A 1,1-dichloropropene B 2,3-dichloropropene C 1,2-dichloropropane D 1,3-dichloropropane
Answer this question and get it marked →May–June 2025, Paper 13
The equation shows the overall reaction between an amine and an acid chloride. 2CH3CH2NH2 + CH3CH2COCl → CH3CH2CONHCH2CH3 + CH3CH2NH3Cl The four steps in the mechanism are shown…
Answer this question and get it marked →Ethanal reacts with KCN dissolved in liquid HCN. This reaction involves the formation of an intermediate. Which statement is correct? A HCN does not have any lone pairs of…
Answer this question and get it marked →Structural and stereoisomerism should be considered when answering this question. How many alcohols with the molecular formula C5H12O give a yellow precipitate with alkaline…
Answer this question and get it marked →An amine is produced in the following reaction. C2H5I + 2NH3 → C2H5NH2 + NH4I What is the mechanism? A electrophilic addition B free-radical substitution C nucleophilic addition D…
Answer this question and get it marked →Fructose is a sugar with more than one chiral centre. The fructose molecule is shown with X, Y and Z indicating three carbon atoms. Which carbon atoms are chiral centres? A X, Y…
Answer this question and get it marked →May–June 2025, Paper 14
1-chloro-2-methylbutane reacts with sodium cyanide in a nucleophilic substitution reaction. What is the most likely intermediate or transition state in this reaction? A…
Answer this question and get it marked →Testosterone is an optically active organic molecule (structure shown with fused ring system, ketone and alcohol). How many chiral centres are there in one molecule of…
Answer this question and get it marked →Structural isomerism and stereoisomerism should be considered when answering this question. How many isomeric esters of methanoic acid can be made with the molecular formula…
Answer this question and get it marked →May–June 2025, Paper 42
May–June 2025, Paper 44
Atorvastatin is a drug with the molecular formula C₃₃H₃₅FN₂O₅. Its structure includes an amide group, two OH groups, an NH group, an alkene, and a fluorine-substituted aromatic…
Answer this question and get it marked →May–June 2024, Paper 11
Structural isomerism and stereoisomerism should be taken into account when answering this question. The structure of 3-methylcyclobutene is shown: a cyclobutene ring with a methyl…
Answer this question and get it marked →May–June 2024, Paper 12
Compound T has the skeletal formula shown: a branched alkane (an isomer of nonane / C9H20) drawn as a chain with several methyl branches. Which structure is a structural isomer of…
Answer this question and get it marked →A sample of pent-2-en-4-ol, C5H10O, contains all the possible stereoisomers of this compound. How many stereoisomers are there in the sample? A 2 B 3 C 4 D 5
Answer this question and get it marked →May–June 2024, Paper 13
Which alkene shows geometric isomerism? A CH3CH2CH2CH=CH2 B CH3CH2CH=CHCH3 C CH3CH2C(CH3)=CH2 D CH3CH=C(CH3)CH3
Answer this question and get it marked →May–June 2024, Paper 21
V shows stereoisomerism (see Fig. 6.1). Explain what is meant by stereoisomerism.
Answer this question and get it marked →May–June 2024, Paper 22
CH3(CH2)5CHBrCH3 exists as a pair of stereoisomers. Draw the three-dimensional structures of the two stereoisomers of CH3(CH2)5CHBrCH3. R can be used to represent CH3(CH2)5.
Answer this question and get it marked →May–June 2024, Paper 41
Neotame is an artificial sweetener added to some foods. (i) State the number of chiral carbon atoms in a molecule of neotame. (ii) Neotame contains the arene functional group.…
Answer this question and get it marked →May–June 2024, Paper 43
Neotame is an artificial sweetener added to some foods. (i) State the number of chiral carbon atoms in a molecule of neotame. (ii) Neotame contains the arene functional group.…
Answer this question and get it marked →October–November 2024, Paper 11
Geraniol and nerol are isomers of each other. They are shown as skeletal/structural formulae. Both have the same carbon skeleton with a CH₂OH group attached to a carbon–carbon…
Answer this question and get it marked →Which compound has the greatest number of stereoisomers? A 2-methylhex-2-ene B 3-methylhex-2-ene C 4-methylhex-2-ene D 5-methylhex-2-ene
Answer this question and get it marked →October–November 2024, Paper 12
Compound X is found in cell walls of some bacteria. Its structural formula is shown. CH₃(CH₂)₁₇CH=CH(CH₂)₁₇CH(OH)CH(CH₃)CO₂H How many stereoisomers are there with this structural…
Answer this question and get it marked →Structural isomerism only should be considered when answering this question. How many straight-chain isomers are there with molecular formula C₄H₈Cl₂? A 6 B 7 C 8 D 9
Answer this question and get it marked →October–November 2024, Paper 13
Geraniol and nerol are isomers of each other. They are shown as skeletal/structural formulae. Both have the same carbon skeleton with a CH₂OH group attached to a carbon–carbon…
Answer this question and get it marked →Which compound has the greatest number of stereoisomers? A 2-methylhex-2-ene B 3-methylhex-2-ene C 4-methylhex-2-ene D 5-methylhex-2-ene
Answer this question and get it marked →October–November 2024, Paper 42
The amino acid serine, HOCH2CH(NH2)COOH, exists in two optically active forms. These optical isomers, isomer P and isomer Q, are shown in Fig. 8.1 as three-dimensional structures…
Answer this question and get it marked →February–March 2023, Paper 12
Which two formulae correctly represent a pair of structural isomers? A CH3CH(CH3)COOH and (CH3)2CHCOOH B CH3CH(COOH)CH3 and (CH3)2CHCOOH C CH3CHCOOH and CH3CH2CH2COOH D…
Answer this question and get it marked →May–June 2023, Paper 11
Structural isomerism and stereoisomerism should be considered when answering this question. If a molecule contains two non-identical chiral carbon atoms, four optical isomers…
Answer this question and get it marked →May–June 2023, Paper 12
Which species is a free radical? A He B Be- C O2- D Zn
Answer this question and get it marked →Which statement about the ClN=O molecule is correct? A Each molecule contains one sigma and one pi bond. B It is a non-polar molecule. C It is a linear molecule. D The nitrogen…
Answer this question and get it marked →Compound X, C5H10O3, has one chiral carbon atom per molecule. Compound X produces bubbles with Na but not with Na2CO3. Which formula could represent compound X? A…
Answer this question and get it marked →May–June 2023, Paper 22
May–June 2023, Paper 41
Some transition element complexes can show stereoisomerism. State two types of stereoisomerism shown by transition element complexes.
Answer this question and get it marked →Compound H has the structural formula CH₂=CHCH(NH₂)COOH. Name all the functional groups in H.
Answer this question and get it marked →May–June 2023, Paper 42
Perindopril is a drug used to treat heart disease (structure shown in Fig. 6.1). State the number of chiral carbon atoms present in one molecule of perindopril.
Answer this question and get it marked →May–June 2023, Paper 43
Some transition element complexes can show stereoisomerism. State two types of stereoisomerism shown by transition element complexes.
Answer this question and get it marked →Compound H has the structural formula CH2=CHCH(NH2)COOH. Name all the functional groups in H.
Answer this question and get it marked →October–November 2023, Paper 11
The compound aspartame is widely used as a sweetener in diet soft drinks. The skeletal structure of aspartame is shown. Aspartame is chiral (there are no chiral carbon atoms in…
Answer this question and get it marked →October–November 2023, Paper 12
How many geometrical (cis/trans) isomers are there of hexa-2,4-diene, CH3CH=CHCH=CHCH3? A: none; hexa-2,4-diene does not show geometric isomerism. B: 2. C: 3. D: 4.
Answer this question and get it marked →October–November 2023, Paper 13
Hexamine is a crystalline solid used as a fuel in portable stoves. The diagram shows its skeletal structure. [A skeletal structure of hexamine is shown: an adamantane-like cage in…
Answer this question and get it marked →The compound aspartame is widely used as a sweetener in 'diet' soft drinks. [The skeletal structure of aspartame is shown. It contains a HOOC-CH2- group, a carbon bearing an NH2…
Answer this question and get it marked →How many sigma and pi bonds are in the molecule HCCCH2CH2CHCH(CH3)2? A 17 sigma 3 pi B 17 sigma 5 pi C 18 sigma 4 pi D 19 sigma 3 pi
Answer this question and get it marked →October–November 2023, Paper 22
Lactic acid, CH3CH(OH)COOH, and pyruvic acid, CH3COCOOH, both contain two functional groups. [Fig. 4.1 shows the displayed structures of lactic acid (a central carbon bearing H,…
Answer this question and get it marked →October–November 2023, Paper 41
Fluorine reacts with chlorine dioxide, ClO₂, as shown: F₂(g) + 2ClO₂(g) → 2FClO₂(g). The rate of the reaction is first order with respect to the concentration of F₂ and first…
Answer this question and get it marked →Capsaicin is found in chilli peppers. Its structure is a methoxy-substituted, hydroxy-substituted benzene ring bonded via a CH₂ group to an N-H of an amide, whose carbonyl is part…
Answer this question and get it marked →October–November 2023, Paper 43
Fluorine reacts with chlorine dioxide, ClO₂, as shown: F₂(g) + 2ClO₂(g) → 2FClO₂(g). The rate of the reaction is first order with respect to the concentration of F₂ and first…
Answer this question and get it marked →Capsaicin is found in chilli peppers. Its structure is a methoxy-substituted, hydroxy-substituted benzene ring bonded via a CH₂ group to an N-H of an amide, whose carbonyl is part…
Answer this question and get it marked →Other AS & A Level Chemistry topics
- Practical skills (106)
- Hydrocarbons (65)
- Chemical bonding (63)
- The Periodic Table: chemical periodicity (59)
- Chemical energetics (53)
- Equilibria (53)
- Reaction kinetics (52)
- Carboxylic acids and derivatives (52)
- Group 2 (51)
- Carbonyl compounds (45)
- Atomic structure (44)
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