3D Hydrocarbon Models – Alkanes, Alkenes, Alkynes, Benzene, and Br₂ Addition
ChemistryOrganic ChemistryAges 16–17
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Organic Chemistry
Ball-and-stick (or space-filling) models of methane, ethane, propane, butane, 2-methylpropane, ethylene, propene, acetylene, and benzene are built automatically with sp³/sp²/sp geometry; drag or touch to rotate. For alkenes and alkynes, click Add Br₂: the Br₂ molecule approaches the multiple bond, the π bond breaks open, one Br atom attaches to each carbon, and the bromine solution loses its color. Compare the C₄H₁₀ isomers side by side. Two more tabs add HBr or H₂O (H₂SO₄) to propene, but-1-ene, 2-methylpropene and but-2-ene, with a curly-arrow panel, carbocation stability, major and minor products by Markovnikov's rule and the peroxide route; and run ozonolysis, whose aldehydes and ketones show where the C=C bond was. An Alkynes tab shows the acidity of terminal alkynes (sodamide, and the precipitates with ammoniacal AgNO₃ and Cu₂Cl₂) and the stepwise addition of H₂ (Lindlar or Ni), HBr and water.
Lesson: Alkanes, unsaturated hydrocarbons (alkenes, alkynes), and arenes – structure and the bromine addition reaction
What it shows
Hybridization sets the shape of a hydrocarbon: sp³ carbons give zigzag alkanes, sp² carbons make ethylene planar, sp carbons make acetylene linear. Alkenes and alkynes add bromine and decolorize bromine water. With an unsymmetrical alkene, HBr or water adds by Markovnikov's rule through the more stable carbocation; a peroxide gives the anti-Markovnikov product. Ozonolysis cuts the C=C bond into two carbonyl compounds. The sp C–H of a terminal alkyne is weakly acidic (pKa about 25): it reacts with sodamide and gives a white silver or red-brown copper(I) precipitate. Alkynes add H₂, HBr and water step by step.
How to use
In Molecules, pick a molecule, drag to rotate and press Add Br₂. In Addition of HX / H₂O, choose the Alkene and Reagent, tick Peroxide present if you like, pick Your prediction of the major product and press React. In Ozonolysis, choose an alkene or press Mystery alkene, then Ozonolysis. In Alkynes, choose the Alkyne and the Reagent and press React; press Add again or Enol → carbonyl for the second step.
Parameters you can change
- Molecule Methane CH₄, Ethane C₂H₆, Propane C₃H₈, Butane C₄H₁₀, 2-Methylpropane C₄H₁₀, Ethylene C₂H₄, Propene C₃H₆, Acetylene C₂H₂, Benzene C₆H₆
- Model style Ball-and-stick, CPK (space-fill, van der Waals radius)
- Auto-rotate
- Show atom labels
- Screen Molecules, Addition of HX / H₂O, Ozonolysis, Alkynes
- Alkene Propene CH₂=CHCH₃, But-1-ene CH₂=CHCH₂CH₃, 2-Methylpropene CH₂=C(CH₃)₂, But-2-ene CH₃CH=CHCH₃
- Reagent HBr, H₂O with H₂SO₄
- Peroxide present (HBr only)
- Alkyne Ethyne HC≡CH, Propyne CH₃C≡CH, But-2-yne CH₃C≡CCH₃
- Reagent for the alkyne Sodamide NaNH₂, AgNO₃ in NH₃, Cu₂Cl₂ in NH₃, H₂, Lindlar catalyst, H₂, Ni catalyst, HBr, H₂O, HgSO₄, H₂SO₄
Questions to explore
- Why do all six atoms of ethylene lie in one plane, while the atoms of ethane do not?
- Could bromine water distinguish ethane from ethylene, and what would you observe with each?
- How do butane and 2-methylpropane differ in structure, even though both have the formula C₄H₁₀?
- Why does propene give mainly 2-bromopropane with HBr, but mainly 1-bromopropane when a peroxide is present?
