## Molecular gymnastics in 2+2 cycloadditions. Two different moves compared.

The previous post showed how the 2+2 cycloaddition of an alkene could occur by a sort of sideways insinuation of the bonds. I have also shown how the same reaction can occur with a dramatic rotation of one of the double bonds. This post compares the two moves side by side.

 0.0 5.3 kcal/mol The forbidden dance The allowed dance.

As is sometimes the case in real life, the forbidden option has the lower activation barrier!

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