Homologous series and isomers builder sim
Build molecules atom by atom, check and name them, find every isomer of a formula, test for C=C with bromine water and compare boiling points across five series.
Organic chemistry: homologous series, naming and structural isomers · covers the O-Level, IGCSE, GCSE topic
What the sim shows
A homologous series is a family with the same general formula and functional group. Each member differs from the next by CH₂, so members have similar chemical properties and a steady trend in physical properties. Build a molecule atom by atom: carbon makes 4 bonds, oxygen 2, hydrogen 1. Check names it, gives Mr (C 12, H 1, O 16) and plots its boiling point. Boiling point rises down every series because longer molecules have stronger forces between molecules; alcohols and acids boil far higher than alkanes of the same length, and branched isomers boil lower than the straight chain. Bromine water goes from orange-brown to colourless with alkenes (C=C) and stays orange-brown with alkanes. Nothing runs on its own: each button press is one step. How it is worked out and its limits: valency is enforced exactly; only single and double bonds, no rings. Names follow the syllabus subset: one main chain, the group given the lowest number, methyl branches only, up to C10; esters only from methanol–butanol and methanoic–butanoic acid. Other valid molecules are accepted but not named. Isomers are structural only, so but-2-ene counts once (bp about 1–4 °C, cis/trans). The C₄H₈ count covers alkenes only (no cyclobutane) and the C₃H₇OH count alcohols only (no methoxyethane). In CₙH₂ₙ₊₁COOH, n is one less than the number of carbons. Boiling points at 1 atm from the CRC Handbook of Chemistry and Physics (97th ed.), rounded. The 3D shapes are idealised (109.5° and 120°, not to scale). The bromine test assumes no UV light; the share of bromine taken by a floating layer uses an estimated partition coefficient (K = 25). Viscosity and flammability trends are in words only.
- Index mark: drag the model sideways to turn it
- Atoms in CPK colours: C black (4 bonds), H white (1), O red (2)
- Bromine water: orange-brown, decolourised by C=C
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