The shape of the lesson
By the end of the lesson, learners can
- Eight groups to recognise: Pick each A Level functional group in the simulator and see it highlighted on a molecule, then watch how the suffix or prefix changes the name.
- Locants on the ring: Two or more substituents on a benzene ring need numbers.
- Phenol: OH directly on the ring; that carbon is C1.
- Acyl chloride, amide, nitrile: count the functional carbon in the stem.
- Amines: 1, 2 or 3 carbon groups on N.
- Ring locants: lowest set, alphabetical order.
One picture every idea returns to
At A Level the organic toolkit grows. An arene contains a benzene ring (C6H5– is the phenyl group); a halogenoarene has a halogen joined directly to the ring; a phenol has –OH joined directly to the ring. Acyl chlorides (RCOCl), amides (RCONH2) and nitriles (RCN) are named from the parent acid or alkane, counting the functional carbon. Amines are classified by the number of carbon groups bonded to the nitrogen: one (primary, RNH2), two (secondary, R2NH) or three (tertiary, R3N). An amino acid has both –NH2 and –COOH, and 2-amino acids carry both on the same carbon. On a benzene ring, substituents get locants numbered to be as low as possible, as in 1,3-dinitrobenzene.
Forty-five minutes, phase by phase
| Time | Phase | What happens in the room | Grouping |
|---|---|---|---|
| 0 to 5 min | Hook: predict | Open with the question in the title, New groups, same naming rules.. The A Level year brings benzene rings, phenols, acyl chlorides, amines, amides and amino acids. Put the figure on the board: it is the one picture every idea in the lesson returns to. | Whole class, then pairs |
| 5 to 17 min | Teach and check: Eight groups to recognise | Pick each A Level functional group in the simulator and see it highlighted on a molecule, then watch how the suffix or prefix changes the name. Project tab 1 of the lab (Organic chemistry (A Level introduction) lab, eight A Level groups) and let a student drive it while the class predicts. | Whole class, then pairs |
| 17 to 30 min | Teach and check: Locants on the ring | Two or more substituents on a benzene ring need numbers. Project tab 2 of the lab (Organic chemistry (A Level introduction) lab, locants on the ring) and let a student drive it while the class predicts. | Mix-Pair-Share |
| 30 to 36 min | Check | The four Stage 1 questions from the student lesson, answered on mini whiteboards or by show of fingers. Re-teach the one most get wrong. | Individual, then whole class |
| 36 to 43 min | Plenary | The exam-style questions from Stage 2, one at a time: thirty seconds alone, then a random call. The feedback lines in the key give the examiner's wording. | Individual, random call |
| 43 to 45 min | Exit and homework | Set the worksheet below (6 questions, 16 marks). Learners self-assess against the objectives before they leave. | Individual |
Protect the parts that carry the learning
The sequence carries about fifty minutes of material, so the lab is driven by one student while the class predicts rather than explored freely. Times are a guide.
Protected: the check at 30 minutes. It is the only individual read on whether the key idea landed, and it is not cut.
Cut first if the build overruns: the last check in Locants on the ring, never the check or the plenary.
In a 60 minute block: run worksheet questions 1 to 3 in class as a Rally Coach set and model both the hardest worked example and its check live.
Mix-Pair-Share
Students mix around the room until you call pair; they pair with the nearest classmate, discuss the prompt, then mix again. Three prompts of rising difficulty, three different partners.
The full structure, with its variations and the other twelve, is on the cooperative-learning page.
What to head off, and how
| Trap learners fall into | Teaching move that pre-empts it |
|---|---|
| Amines are classified by counting the carbon groups on the nitrogen, not by the type of carbon the nitrogen is on: (CH 3) 3 CNH 2 is a primary amine even though it would be a tertiary alcohol if the NH 2 were OH. | Phenol has –OH directly on the ring; C 6 H 5 CH 2 OH is an alcohol (phenylmethanol). Chlorobenzene is a halogenoarene; C 6 H 5 CH 2 Cl, with Cl on a side chain, behaves like a halogenoalkane. |
A Level functional groups and naming: worksheet
6 questions, 16 marks. Written in the style of the papers; no past paper question is reproduced.
Name the homologous series of each compound: (a) C6H5Br, (b) CH3CH2COCl, (c) CH3CH2CONH2, (d) CH3CH2CN.
Classify each amine as primary, secondary or tertiary: (a) CH3CH2NHCH3, (b) C6H5NH2, (c) (C2H5)3N.
Draw or describe 1,3-dinitrobenzene and explain why it is not called 1,5-dinitrobenzene.
Calculate the percentage by mass of nitrogen in 1,3-dinitrobenzene, C6H4(NO2)2.
Explain why C6H5OH is a phenol but C6H5CH2OH is an alcohol.
2-aminopropanoic acid has the formula CH3CH(NH2)COOH. Identify its two functional groups and explain the number 2 in the name.
Answer key and marking notes
- (a) halogenoarene (bromobenzene).
- (b) acyl chloride (propanoyl chloride).
- (c) amide (propanamide).
- (d) nitrile (propanenitrile).
- (a) secondary: two carbon groups (ethyl and methyl) on N.
- (b) primary: one carbon group (phenyl) on N; this is phenylamine.
- (c) tertiary: three ethyl groups on N.
- A benzene ring with NO2 groups on carbons 1 and 3, with one ring carbon between them.
- Numbering the other way round gives 1,5, but the rule is to use the lowest set of locants.
- Mr = 6(12.0) + 4(1.0) + 2(14.0) + 4(16.0) = 168.0.
- %N = 28.0 ÷ 168.0 × 100 = 16.7%.
- In C6H5OH the OH is bonded directly to a carbon of the benzene ring.
- In C6H5CH2OH the OH is on a CH2 side-chain carbon, so it is a primary alcohol (phenylmethanol).
- It has a primary amine group, –NH2, and a carboxylic acid group, –COOH.
- The chain is numbered from the COOH carbon, which is C1.
- The NH2 is on C2, the carbon next to COOH, so it is a 2-amino acid.
8 multiple-choice questions on this lesson
From the topic question bank. Assign them in the app for a marked score in your gradebook, or run the topic as a class game.
What is the systematic name of CH3CH2COCl?
- Apropanoyl chloride
- Bethanoyl chloride
- Cpropyl chloride
- D1-chloropropanone
How is diethylamine, (CH3CH2)2NH, classified?
- Asecondary amine
- Bprimary amine
- Ctertiary amine
- Dsecondary amide
The diagram shows a substituted benzene. What is its name?
- A1,3-dinitrobenzene
- B1,5-dinitrobenzene
- C1,4-dinitrobenzene
- D1,2-dinitrobenzene
Which compound is a halogenoarene?
- AC6H5Cl
- BC6H5CH2Cl
- CC6H11Cl
- DCH3COCl
What is the name of CH3CH2CN?
- Apropanenitrile
- Bethanenitrile
- Cbutanenitrile
- Dpropylamine
N-phenylethanamide has the structure CH3CONHC6H5. Which functional group does it contain?
- Aa secondary amide
- Ba primary amine
- Can ester
- Da ketone
What is the percentage by mass of nitrogen in phenylamine, C6H5NH2? (Ar: H 1.0, C 12.0, N 14.0)
- A15.1%
- B18.2%
- C7.53%
- D30.1%
Phenol reacts with bromine water. Bromine atoms replace the H atoms on both ring carbons next to the C–OH carbon and on the carbon opposite it. What is the name of the product?
- A2,4,6-tribromophenol
- B1,3,5-tribromophenol
- C2,3,4-tribromophenol
- D2,4,6-tribromocyclohexanol
Quiz key
The chain has three carbons and ends in the acyl chloride group –COCl, so it is propanoyl chloride. Ethanoyl chloride, CH3COCl, has only two carbons: that name forgets to count the C=O carbon. Propyl chloride would be CH3CH2CH2Cl, a halogenoalkane with no C=O. 1-chloropropanone would need a ketone with Cl on a CH2 carbon, ClCH2COCH3, which is a different compound.
Two ethyl groups are bonded to N, with one H, so it is a secondary amine (R2NH). A primary amine has one carbon group on N (RNH2) and a tertiary amine has three (R3N). An amide needs the nitrogen joined to a C=O carbon, and there is no C=O here.
The two NO2 groups have one ring carbon between them. Numbering from the top group and going clockwise puts the second on C3, giving 1,3-dinitrobenzene. Going anticlockwise gives 1,5, which is the same molecule but not the lowest set of locants. 1,4 would put the groups on opposite carbons, and 1,2 on neighbouring carbons.
Chlorobenzene, C6H5Cl, has Cl joined directly to the ring, so it is a halogenoarene. In C6H5CH2Cl the Cl is on a side-chain CH2, so it behaves as a halogenoalkane. C6H11Cl is chlorocyclohexane: the ring is saturated, not a benzene ring. CH3COCl is an acyl chloride.
There are three carbons including the nitrile carbon, so the name is propanenitrile. Ethanenitrile is CH3CN, which forgets to count the C≡N carbon. Butanenitrile has four carbons, CH3CH2CH2CN. Propylamine, CH3CH2CH2NH2, is the amine formed when propanenitrile is reduced; it has a single C–N bond, not a triple bond.
The N is bonded to a C=O carbon and to one carbon group (phenyl) as well as one H, so this is a secondary amide; the N- prefix shows the phenyl is on nitrogen. A primary amine would have NH2 on a carbon that is not a C=O carbon, as in phenylamine. An ester has –COO– with no nitrogen. A ketone has C=O between two carbons, but here the C=O carbon is bonded to N.
Mr = 6(12.0) + 7(1.0) + 14.0 = 93.0, so %N = 14.0 ÷ 93.0 × 100 = 15.1%. 18.2% uses Mr = 77.0, the phenyl group only, leaving out NH2. 7.53% uses half the Ar of nitrogen. 30.1% doubles it, as if there were two N atoms.
Numbering starts at the C–OH carbon (C1), so the neighbouring carbons are C2 and C6 and the opposite carbon is C4: 2,4,6-tribromophenol. 1,3,5 numbers from a Br carbon instead of the OH carbon, which is not allowed for a phenol. 2,3,4 would put the Br atoms on three adjacent carbons. Substitution keeps the aromatic ring, so the product is still a phenol, not a cyclohexanol.
What to project
The student lesson embeds these tabs. Open them full screen on the projector; every slider has a drag handle on the stage.
Slides for this lesson
A projectable deck for every pack is on the way. Until then, present the student lesson full screen: its sections, figure and lab tabs follow the same order as the plan above.