‹ Chemistry simulationsChemistry · A Level 9701 · 31 HalogenoarenesFour simulations covering Topic 31: chlorobenzene made by electrophilic substitution with Cl⁺ from Cl₂ and a halogen carrier, set beside the addition an alkene would do; why the C-Cl bond in chlorobenzene is short and strong, with the chlorine lone pair overlapping the ring; a hydrolysis race with hot aqueous silver nitrate in ethanol that chloroethane, bromoethane and iodoethane win and chlorobenzene never does; and the ring itself still reacting, with nitration giving the 2- and 4-isomers and the harsh route to phenol.
Benzene will not react with chlorine on its own, because the delocalised ring is stable and chlorine is not a strong enough electrophile. A halogen carrier such as aluminium chloride or iron(III) chloride pulls Cl⁻ off a chlorine molecule and leaves Cl⁺, which the ring can attack. On the right, ethene reacts with the same chlorine and needs no help. Step through both.
A lone pair on the chlorine sits in a p orbital that points above and below the ring, exactly like the p orbitals of the ring carbons. They overlap, so the lone pair spreads into the pi system and the C-Cl bond gains some double-bond character. That makes it shorter and stronger than in chloroethane, and it also leaves nowhere for a nucleophile to attack.
Warm each compound in ethanol with aqueous silver nitrate. If the C-X bond breaks, water takes the halogen away as X⁻, and Ag⁺ catches it as a silver halide precipitate. The faster the precipitate appears, the weaker the bond. Start the clock and watch which tubes cloud over, and which never do.
Chlorobenzene resists attack on its C-Cl bond, but its ring is still a ring of delocalised electrons, and electrophiles still go for it. Nitrate it and you get a mixture of 2- and 4-nitrochlorobenzene, a little slower than benzene itself. The only way to swap the chlorine for OH is to go to extreme conditions.
Four interactive simulations for Cambridge A Level Chemistry 9701 topic 31 Halogenoarenes: electrophilic substitution of benzene by Cl+ from Cl2 with an AlCl3 or FeCl3 halogen carrier stepped through in 3D beside the addition of chlorine to ethene, the C-Cl bond in chlorobenzene with the chlorine lone pair delocalising into the ring compared with chloroethane in terms of bond length, bond enthalpy and electron density, a hydrolysis race of chloroethane, bromoethane, iodoethane and chlorobenzene with hot aqueous silver nitrate in ethanol, and the nitration of chlorobenzene to 2- and 4-nitrochlorobenzene with the 2,4-directing and deactivating effect of chlorine plus the high temperature, high pressure route to phenol.
Four simulations covering Topic 31: chlorobenzene made by electrophilic substitution with Cl⁺ from Cl₂ and a halogen carrier, set beside the addition an alkene would do; why the C-Cl bond in chlorobenzene is short and strong, with the chlorine lone pair overlapping the ring; a hydrolysis race with hot aqueous silver nitrate in ethanol that chloroethane, bromoethane and iodoethane win and chlorobenzene never does; and the ring itself still reacting, with nitration giving the 2- and 4-isomers and the harsh route to phenol.
Halogenoarenes is a free, browser-based simulation for Cambridge International AS & A Level Chemistry 9701 (topic 31 Halogen compounds). The course is assessed in Paper 1 (Multiple Choice (AS)), Paper 2 (AS Structured), Paper 3 (Advanced Practical), Paper 4 (A Level Structured), Paper 5 (Planning, Analysis, Evaluation). Syllabus for examination in 2025-2027. There are 4 tabs, each a self-contained experiment with its own controls and live readings, and nothing to install: it runs on a laptop, tablet or classroom projector.
Full syllabus map: A Level Chemistry 9701 topic 31.
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