Vicinal 1,2 interchange

There are many enzymes that need a cobalt complex as cofactor in order to carry out vicinal 1,2 interchange ... 

Fig. 3. The vicinal interchange reaction of coenzyme B12-dcpendent rearrangements.

Patterson S, O Hagan D. Biosynthetic studies on the tropane alkaloid hyoscyamine in Datura stramonium hyoscyamine is stable to in vivooxidtion and is not derived from Uttorine via a vicinal interchange process. Phytochemistry 2002 61 323-329. 

In the next reaction, the tropate ester moiety of hyoscyamine is derived by condensation of tropine with the phenylalanine-derived (/ )-phenyllactate to form littorine 26 [7,37]. Patterson and O Hagan [39] suggested that the rearrangement of littorine 26 into hyoscyamine 1 does not occur with a vicinal interchange process as previously considered. Recently, a multifunctional cytochrome P450 has been identified from H. niger L., classified as Cyp80Fl and catalyzes the oxidation of... 

E. J. Corey, N. J. Cooper, and M. L. H. Green (1977), Biochemical catalysis involving coenzyme B12 A rational stepwise mechanistic interpretation of vicinal interchange rearrangements. Proc. Nat. Acad. Sci. USA 74, 811-815. 

In a review of the subject, Ubbelohde [3] points out that there is only a relatively small amount of data available concerning the properties of solids and also of the (product) liquids in the immediate vicinity of the melting point. In an early theory of melting, Lindemann [4] considered that when the amplitude of the vibrational displacements of the atoms of a particular solid increased with temperature to the point of attainment of a particular fraction (possibly 10%) of the lattice spacing, their mutual influences resulted in a loss of stability. The Lennard-Jones—Devonshire [5] theory considers the energy requirement for interchange of lattice constituents between occupation of site and interstitial positions. Subsequent developments of both these models, and, indeed, the numerous contributions in the field, are discussed in Ubbelohde s book [3]. 

Water in food products can be described as being free or bound. The definition of what consitiutes bound water is far from clear (see Fennema, 1985) but it can be considered as that part of the water in a food which does not freeze at — 40°C and exists in the vicinity of solutes and other non-aqueous constituents, has reduced molecular mobility and other significantly altered properties compared with the bulk water of the same system (Fennema, 1985). The actual amount of bound water varies in different products and the amount measured is often a function of the assay technique. Bound water is not permanently immobilized since interchange of bound water molecules occurs frequently. 

The term has also been used interchangeably with the term transition coordinate, applicable to the coordinate in the immediate vicinity of the potential energy maximum. Being more specific, the name transition coordinate is to be preferred in that context. 

The low reactivity of the rhodium clusters is surprising if one assumes that aryl group interchange can occur between vicinal metal centers as is proposed by Kaneda et al. (5). It is possible however that the rhodium clusters used here are rather coordinatively and structurally stable and do not promote aryl interchange at the employed temperatures. At the higher temperatures however, cluster breakdown to reactive mononuclear species and/or coordinatively unsaturated clusters is likely. 

The fact that an electronic state must be antisymmetric under interchange of any two electrons is an expression of the Pauli Principle. It implies also that no two electrons are allowed to be in exactly the same 1-electron state for if we replace V b by a second ipA the antisymmetric combination disappears In a many-electron atom, say, the state of lowest energy (the ground state ) must have electrons spread over different 1-electron states Vu, b> , not more than one in each, even if the energy of the A state is lower than all the others. Were it not for the antisymmetry restriction, the ground state would be the one in which all electrons crowded into i a- atoms would show no shell structure and would collapse into dense and compact clouds of electrons, in the immediate vicinity of their nuclei. It can be argued that the Pauli Principle is perhaps the most important single principle in the whole of physics were it not valid there would be no atoms, no chemistry, no life, no universe as we know it. 

Very often the terms dihedral and torsional are used interchangeably. In a later section, discussing explicit dihedral potentials, we shall specifically reserve the term torsional for an internal rigid rotation, and the term dihedral for the rotation of two vicinal bonds about a middle bond. 

It is isomeric with thalictrifoline and has the same functional groups. When demethylenated with phloroglucinol and sulfuric acid it yields a dihydroxy base (m.p. 246°, in vacuo) which on methylation is converted into corydaline. Thalictricavine is therefore either steroisomeric with thalictrifoline or it is thalictrifoline with the pairs of vicinal ether groups interchanged as in LXVI. 

When an ionic compound dissolves in a polar solvent such as water, the ions become strongly solvated. The ion-dipole forces produce a layer of solvent molecules (the primary solvation sphere) surrounding each ion. This layer can cause other solvent molecules in the immediate vicinity to become oriented as well. Although the primary solvation sphere may seem to be rather firmly attached to the ion, there is considerable interchange between these molecules and the bulk solvent in a dynamic process in most cases. For strongly solvated ions like [Cr(H206] , the exchange of coordinated water molecules and those of the bulk solvent is very slow. As we shall describe later, some desolvation of ionic species may be required before a reaction of the ion can take place. 

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