A site for drawing 2D and 3D structures online. It looks like it will be useful for students, but read the comments under Read More when the warning "The resolved 3D structure can sometimes be inaccurate" appears. It explains when and why the structure might be incorrect. It also explains how to fix potential problems.
Why is 1,4-cyclohexadiene stabilized? Using qualitative perturbation theory to teach conjugation
Six-carbon polyenes display quite regular properties, when one compares their stabilities using hydrogenation enthalpies. Each double bond in a conjugated system is worth about 10 kJ/mol in resonance energy, and non-conjugated dienes show no resonance energy. Cyclohexadienes are puzzling: 1,3-cyclohexadiene is less stable, and 1,4-cyclohexadiene is more stable, than corresponding open-chain dienes. Qualitative molecular orbital perturbation theory can be used to explain these anomalies.
This is an iPad app (only for iPad, I'm afraid!) sponsored by the Chemical Heritage Foundation.
What it does is to simulate an old-time chemistry set, with all the dangerous chemicals. You start with alkali metals in water, and work your way up to heating reactive metals in air with a blowtorch, and mixing alkalic metals with halogens. There's a strong emphasis on BOOM.
Unfortunately this is not suitable for classroom use, at least for me, because you can't get random access to particular reactions. But it is a lot of fun to play with, and perfectly suitable (recommended) for children.
The YouTube promotional video is below.
This very sophisticated page developed by Otis Rothenberger gives you all the presence of a physical molecular model but with all sorts of additional features. These additional features include the ability to search and load molecules from the protein data bank, PubChem, or the NIH/NCI Chemical Identifier resolver.
Java-based software for drawing chemical structures
Superb software to draw structures. It converts structutres to names, and visa versa, and predicts 1H and 13C chemical shifts.