Scrambling theory

One of the most intriguing features of olefin metathesis, and an aspect which continues to receive increasing attention, is the stereochemistry of the reaction. Rationalizations of stereochemical peculiarities have undergone a metamorphosis which parallels advances of mechanistic theories from the pairwise scrambling schemes to the now-popular car-bene-to-metallocycle scheme. As yet there exists no unified stereochemical model which can adequately account for all the observed results. 

Table 3. Relative Energies (in kcal mol ) of the CHj Transition Structures for Hydrogen Scrambling, 2 and 3 (A = C), Relative to 1 (Energetic Reference Point) at Different Levels of Theory.

E. Brandas, N. Elander, Energy Scrambling Out in the Continuum Weyl s Theory and Predissociation, in J. Hinze (Ed.), Proceedings Bielefeld Symposium on Energy Storage and Redistribution in Molecules, Plenum Press, New York, 1983, p. 543. 

Suppose now that we allow the orbitals to interact. The ultimate result will be a scrambling of the orbitals to give in the end the same set of many-center MO s that would be obtained by a normal LCAO MO treatment.49 Let us, however, consider the interactions in terms of perturbation theory. There will be a first order perturbation to the degenerate set of MO s yBl due to their mutual interaction. Writing the perturbed energy of the... 

Labelled reticuline was readily incorporated into thebaine 14, codeinone 15a, codeine 15b, and morphine 16 without scrambling of the labels. Salutaridine is not present in detectable quantities in Papaver somniferum. However, when appropriately labelled, it is well incorporated into morphine alkaloids. Salutaridine can be readily reduced to two stereo-isomeric allylic alcohols 17, both of which are converted by mild acid catalysis (17, see arrows) to give thebaine 14. The alkaloids 17, 14, 15a, and 15b were all shown to be precursors of morphine. This was of interest, because the earlier theory of Robinson suggested that unmethylated alkaloids were first assembled and methylation was a terminal stage of biosynthesis. 

CPT symmetry is deeply embedded in fundamental physics. One can prove that quantum field theory and special relativity (as we currently understand these theories) respect CPT symmetry. If CPT were to be proven invalid, contemporary physics would be scrambled. 

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