Content deleted Content added
Line 6:
==Thermal cycloadditions and their stereochemistry==
Thermal cycloadditions are those cycloadditions where the reactants are in the ground electronic state. They usually have (4''n'' + 2) π electrons participating in the starting material, for some integer n. These reactions occur for reasons of [[orbital symmetry]] in a [[suprafacial]]-suprafacial or [[antarafacial]]-antarafacial manner (rare). There are a few examples of thermal cycloadditions which have 4''n'' π electrons (for example the [2 + 2] cycloaddition). These proceed in a suprafacial-antarafacial sense, such as the dimerisation of [[ketene]], in which the [[orthogonal]] set of [[p orbital]]s allows the reaction to proceed via a crossed [[transition state]]
==Photochemical cycloadditions and their stereochemistry==
| |||