The shape of the lesson
By the end of the lesson, learners can
- Name it, then draw it: Pick a stem and an ending in the simulator and check that your displayed formula matches the name.
- Structural isomers: Extended.
- Stems: meth 1, eth 2, prop 3, but 4 (count the −COOH carbon too).
- Endings: -ane, -ene, -ol, -oic acid.
- Extended: esters are alcohol-yl acid-oate: ethyl ethanoate.
- Extended: isomers = same molecular formula, different structural formula.
One picture every idea returns to
The stem counts the carbon atoms in the chain: meth- 1, eth- 2, prop- 3, but- 4. The ending names the homologous series: -ane for alkanes, -ene for alkenes, -ol for alcohols and -oic acid for carboxylic acids. A number shows where the functional group sits when it could be in more than one place, as in propan-1-ol or but-2-ene. (Extended) An ester is named alcohol part first (ending -yl) then acid part (ending -oate): ethanol + ethanoic acid gives ethyl ethanoate. (Extended) Structural isomers have the same molecular formula but different structural formulae, such as butane and methylpropane (both C4H10).
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, Stem plus ending.. Every organic name is built from two parts: a stem that counts the carbon atoms and an ending that names the family. 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: Name it, then draw it | Pick a stem and an ending in the simulator and check that your displayed formula matches the name. Project tab 2 of the lab (Organic chemistry lab, naming) and let a student drive it while the class predicts. | Whole class, then pairs |
| 17 to 30 min | Teach and check: Structural isomers | Extended. Project tab 3 of the lab (Organic chemistry lab, structural isomerism) and let a student drive it while the class predicts. | Think-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, 14 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 Structural isomers, 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.
Think-Pair-Share
Pose the question, give thirty seconds of silent thinking, then a minute to compare with a partner before a few pairs share with the class. The silent minute is the part that cannot be cut.
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 |
|---|---|
| A chain drawn with a bend is the same molecule, not an isomer: follow the bonds, not the shape on the page. | Name the longest unbroken carbon chain, so a "bent butane" is still butane. In esters the alcohol gives the first word (ethyl) and the acid gives the second (ethanoate), the reverse of the order in the word equation. |
Naming organic compounds: worksheet
6 questions, 14 marks. Written in the style of the papers; no past paper question is reproduced.
Name: (a) CH3CH2CH2CH3; (b) CH3CH=CH2; (c) CH3CH2OH; (d) HCOOH.
Draw the displayed formula of propanoic acid.
Give the structural formula and name of the alcohol with four carbon atoms and the −OH group on the end carbon.
(Extended) Name the ester formed from methanol and ethanoic acid and give its structural formula.
(Extended) Define structural isomers and give the names of two structural isomers with formula C4H10.
(Extended) A student says CH3CH2CH2OH and CH3CH(OH)CH3 are the same compound because both are C3H8O. Explain why the student is wrong and name both compounds.
Answer key and marking notes
- (a) butane.
- (b) propene.
- (c) ethanol.
- (d) methanoic acid.
- CH3−CH2− chain with all C−H bonds drawn (3 H on the first carbon, 2 H on the second).
- Third carbon has C=O and C−O−H: every carbon has four bonds.
- CH3CH2CH2CH2OH.
- Butan-1-ol.
- Methyl ethanoate (alcohol part methyl, acid part ethanoate).
- CH3COOCH3.
- Compounds with the same molecular formula but different structural formulae.
- Butane and methylpropane.
- The −OH group is on a different carbon atom, so the structural formulae differ: they are structural isomers, not the same compound.
- Propan-1-ol and propan-2-ol.
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 name of CH3CH2CH3?
- Apropane
- Bpropene
- Cethane
- Dbutane
Which compound is an alcohol?
- ACH3CH2OH
- BCH3COOH
- CCH2=CH2
- DCH3CH3
What is the name of CH3CH2COOH?
- Apropanoic acid
- Bethanoic acid
- Cpropanol
- Dbutanoic acid
Which is the structural formula of butene with the double bond at the end of the chain (but-1-ene)?
- ACH2=CHCH2CH3
- BCH3CH2CH2CH3
- CCH2=CHCH3
- DCH3CH2CH2CH2OH
Which pair shows the name endings for alcohols and carboxylic acids correctly?
- Aalcohol: -ol; carboxylic acid: -oic acid
- Balcohol: -ane; carboxylic acid: -ene
- Calcohol: -oic acid; carboxylic acid: -ol
- Dalcohol: -ene; carboxylic acid: -ol
Which ester is formed when propan-1-ol reacts with ethanoic acid?
- Apropyl ethanoate
- Bethyl propanoate
- Cpropyl propanoate
- Dethyl ethanoate
Which ester has the structural formula HCOOCH3?
- Amethyl methanoate
- Bmethyl ethanoate
- Cethyl methanoate
- Dmethanoic acid
Propan-1-ol, CH3CH2CH2OH, has a structural isomer that is also an alcohol. What is it?
- Apropan-2-ol, CH3CH(OH)CH3
- Bpropanoic acid, CH3CH2COOH
- Cethanol, CH3CH2OH
- Dpropene, CH2=CHCH3
Quiz key
Three carbon atoms gives the stem prop-, and only single bonds gives the ending -ane, so it is propane. Propene would have a C=C double bond (C3H6). Ethane has two carbons and butane has four.
CH3CH2OH is ethanol, which has the −OH group. CH3COOH also contains O and H, but as part of −COOH, which makes it a carboxylic acid (ethanoic acid). CH2=CH2 is ethene, an alkene, and CH3CH3 is ethane, an alkane.
Counting the COOH carbon, the chain has three carbons, so the name is propanoic acid. Ethanoic acid (CH3COOH) has only two carbons: forgetting to count the COOH carbon gives this wrong answer. Propanol is an alcohol with an −OH group. Butanoic acid has four carbons.
CH2=CHCH2CH3 has four carbons and a C=C bond between carbons 1 and 2, so it is but-1-ene. CH3CH2CH2CH3 has no double bond (butane). CH2=CHCH3 has only three carbons (propene). The last option is butan-1-ol, an alcohol.
Alcohols end in -ol (ethanol) and carboxylic acids end in -oic acid (ethanoic acid). The endings -ane and -ene belong to alkanes and alkenes. Swapping -ol and -oic acid mixes up the two series.
In an ester name the alcohol part comes first and ends in -yl, and the acid part comes second and ends in -oate. Propanol gives propyl and ethanoic acid gives ethanoate: propyl ethanoate. Ethyl propanoate swaps the two parts (it would come from ethanol and propanoic acid). Propyl propanoate and ethyl ethanoate each use only one of the two reactants.
HCOO− comes from methanoic acid (one carbon, counting the C=O carbon) and −CH3 on the oxygen comes from methanol, so the ester is methyl methanoate. Methyl ethanoate is CH3COOCH3, with two carbons on the acid side. Ethyl methanoate is HCOOCH2CH3. Methanoic acid is HCOOH, with H on the oxygen, not CH3.
Propan-2-ol has the −OH on the middle carbon. It has the same molecular formula, C3H8O, but a different structure, so it is a structural isomer. Propanoic acid is C3H6O2, ethanol is C2H6O and propene is C3H6; none has the same molecular formula as propan-1-ol.
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.