Synthesis tree definition

Probably the least mechanical and easily defined operation is the initial choice of bondsets as a starting point for the protocol. Criteria for bond selection on grounds of both target functionality and target skeleton are applied but the procedure is still somewhat arbitrary and in need of sharper definition. In view of the enormous size of the synthesis tree this is probably inevitable, but it may be noted that it is no more arbitrary than the traditional description of stepwise retrosynthetic development from target functionality. In that procedure a bondset is also ultimately defined in steps, of course, by the constructions selected from the functionality each time. Such a procedure in fact misses many... 

Using our definition for alkalinity or ANC whereby any decrease (increase) in concentrations of base cations (e.g., K+, Ca2+, Fe2+, etc.) or any increase (decrease) in concentrations of "acid anions" (e.g., NO3, HPO2, SOf, etc.) is accompanied by a decrease (increase) in alkalinity. Thus, as illustrated in Fig. 5.17 net synthesis of terrestrial biomass (e.g., on the forest and forest floor, where more cations than anions are taken up by the plants (trees), is accompanied by a release of H+ to the environment. 

The problem of molecular weight distribution (MWD) and functionality type distribution (FTD) belongs by definition to an extensive problem of molecular heterogeneity of polymers. In the synthesis of a polymer with the requested properties, e.g. a telechelic polymer, one is always faced with different types of polydispersity the macromolecules can be of different length, they can have a different number of functional groups, i.e. be mono-, bifunctional, etc., they can be branched (star-, comb- or tree-like) and, finally, they can be cyclic. 

The second source of complexity, that of the many possible combinations of bonds to create may be handled in the other way, i.e., by decomposing the tree into independent subtrees. The simplest gross definition of a particular s5mthesis is the bondset, the set of skeletal bonds or links (A in number) which me actually constructed in that synthesis i6). To illustrate this, three steroid syntheses are depicted as bondsets of A =3,6 and 8, respectively, in structures 1, 2 and 3 25). 

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