Acceptor products, structures

Research of the structures of alternansucrase acceptor products arising from D- 50... 

M. Dols, M. Remaud-Simeon, R. M. Willemot, M. Vignon, and P. Monsan, Structural characterization of the maltose acceptor products synthesized by Leuconostoc mesenteroides NRRL B-1299 dextransucrase, Carbohydr. Res., 305 (1998) 549-559. 

Fig. Structures of some acceptor products of B-512F dextran...

The products are those produced by Leuc. mesenteroides B-512F dextransucrase unless otherwise indicated. b The starred products are also acceptors that give a homologous series with a-isomalto-oligosaccharides attached to the acceptor.r Structure not determined.d Two products are formed by Leuc. mesenteroides B-512F dextransucrase. Not an acceptor. Four products are formed by Strep, mutans GTF-I. Product formed by altemansucrase. 

Intramolecular conjugate addition naturally results in ring formation. The body of examples of this type of reaction is subdivided into the Sections 4.7.1.1.2.1. Acyclic Acceptors and 4.7.1.1.2.2. Cyclic Acceptors , depending on whether or not the accepting enone/enoate moiety is part of a ring system. In the latter case, the cyclization affords a bi- or oligocyclic product. The steric restrictions thus imposed reduce the number of thermodynamically feasible products. As a consquence, product structures can usually be predicted easily, and high stereoselectivities are observed. 

Table 14.4. Expansion coefficients Co(i) at the acceptor-donor structures in the ground-state wave function at various stages of the 8 2 substitution reaction of ethylene reactant (R), intermediate (I), and product (P). The most important contributions are in bold. ...

This last reaction is typical of many in which F3CIO can act as a Lewis base by fluoride ion donation to acceptors such as MF5 (M = P, As, Sb, Bi, V, Nb, Ta, Pt, U), M0F4O, Sip4, BF3, etc. These products are all white, stable, crystalline solids (except the canary yellow PtFe ) and contain the [F2CIO] cation (see Fig. 17.26h) which is isostructural with the isoelectronic F2SO. Chlorine trifluoride oxide can also act as a Lewis acid (fluoride ion acceptor) and is therefore to be considered as amphoteric (p. 225). For example KF, RbF and CsF yield M [F4C10] as white solids whose stabilities increase with increasing size of M+. Vibration spectroscopy establishes the C4 structure of the anion (Fig. 17.29g). 

C09-0138. In the following reactions, phosphorus forms a bond to a Row 2 element. In one reaction, phosphoms donates two electrons to make the fourth bond, but in the other reaction, phosphorus accepts two electrons to make the fourth bond. Use Lewis structures of starting materials and products to determine in which reaction phosphoms is a donor and in which it acts as an acceptor. 

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