Sigmatropic Shifts Cope and Claisen Rearrangement

On the basis of stereochemical and kinetic investigations and quantum-mechanical calculations, most Cope rearrangements are regarded as being pericyclic processes [25, 102, 103]. The van der Waals volumes calculated for the parent 1,5-hexadiene 

All volumes are given in cm -raol The structural parameters necessary for the calculation of the van der Waals volume for the transition structure (TS) were taken from ab initio calculations [25,102]. The partial molar volume for the TS was calculated from the equation  

The utility of high pressure in the elucidation of reaction mechanisms can be also demonstrated by the example of the racemization and diastereomerization in 

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