Chemistry 11–12 · Year 12

Building and naming structural isomers with model kits: alkanes, alkenes, alcohols, esters

Module 7: Organic Chemistry

Practical, model not builtLow risk

This site has no interactive model of its own. Where a step or a material names a Concept Studio model, simulation or tool, it has not been built; an external simulation a step names (for example PhET) is not part of this site.

The idea

The same molecular formula can be assembled into different carbon skeletons or functional groups, and each arrangement is a distinct compound with its own IUPAC name and properties.

What you need

Molecular model kits (carbon, hydrogen, oxygen and chlorine centres; single and double bonds), one per pair
Worksheet of formulas: C4H10, C5H12, C6H14, C4H8, C3H7Cl, C4H10O (alcohols only), C3H6O2 (acid and esters only)
Data table of boiling points for the C5H12 isomers, the four C4H10O alcohols and the C3H6O2 acid and esters (secondary source)

How to do it

Build every chain isomer of C4H10 and C5H12; rotate each model to check whether two apparently different models are the same molecule; draw the structural and skeletal formula and give the IUPAC name of each.
Repeat for C6H14 and check the count against the simulation.
Build the position isomers of C3H7Cl and the position and geometric isomers of C4H8 (including cyclic forms if the kit allows).
Build the four alcohols of formula C4H10O and sort them into primary, secondary and tertiary; then build propanoic acid and the two esters of formula C3H6O2 (methyl ethanoate and ethyl methanoate), which are functional group isomers of the acid.
Use the boiling-point table to relate branching and functional group to intermolecular forces.
In the simulation step the carbon number from 1 to 8 and record how fast the number of alkane isomers grows.

What you should see

Chain isomers: C4H10 has 2 (butane, 2-methylpropane), C5H12 has 3 (pentane, 2-methylbutane, 2,2-dimethylpropane) and C6H14 has 5. The model's enumeration gives alkane isomer counts for C1 to C8 of 1, 1, 1, 2, 3, 5, 9, 18, matching OEIS A000602. C3H7Cl has 2 position isomers (1-chloropropane, 2-chloropropane). C4H10O gives four alcohols: butan-1-ol and 2-methylpropan-1-ol (primary), butan-2-ol (secondary) and 2-methylpropan-2-ol (tertiary); its three ether isomers are left out because neither syllabus covers ethers. C3H6O2 gives propanoic acid and the esters methyl ethanoate and ethyl methanoate, functional group isomers of the acid. More branching lowers the boiling point, and propanoic acid boils well above its two ester isomers because its molecules hydrogen bond to one another.

What changes

This activity lists no variables to change, measure and keep the same.

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

Bending a chain makes a new isomer (rotating about single bonds gives the same molecule; only a new connection pattern is a new isomer).
Isomers have the same properties because they have the same formula (branching and functional group change the boiling point and the chemistry).
A carboxylic acid and an ester with the same formula are the same kind of compound (they are functional group isomers with different reactions).

Safety card

Low riskLearners carry it out

Hazards

small model pieces

Controls

kits counted back in at the end

Note

No chemicals are handled and the kits are plastic models, so the NSW Department of Education Chemical Safety in Schools package does not apply; ordinary classroom supervision.

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Chemistry Stage 6 Syllabus (2017), NESA; the current syllabus, taught in 2026 (codes read from the syllabus document)CH12-14 CH11/12-5 CH11/12-6 CH11/12-7
Chemistry 11-12 Syllabus (2025), NESA; implemented from 2028, not yet taughtCH-12-03 CH-12WS-05 CH-12WS-06
Australian Curriculum v9No Australian Curriculum v9 code is listed.

Sources

The pages the author read to write this activity.

All Concept Studio activities