Synthon. definition

Paraphrasing Corey s historic definition of synthon [203], Desiraju defined a supramolecular synthon as a structural unit within a supermolecule that can be formed or assembled by known or conceivable synthetic operations involving intermolecular interactions [204], The robustness of the XB has allowed several supramolecular synthons based on this interaction to be identified and some examples have been presented in this chapter. 

The Definite Clause Grammar (DCG) formalism [7] is utilized throughout this project. Grammar rules are used in the expert system rules to recognize the general class of the parent molecule in the disconnection (c.y., cyclohexene). The class determines the patterns used to construct the resultant synthons (discussed in Section 4). 

Without stepping into any nomenclature controversies, for the purposes of this review, cocrystal systems will be regarded as those mixed crystal systems where the individual components exist as solids under ambient conditions [11]. Aakeroy has summarized guidelines for cocrystal formation from supramolecular synthons as being constructed from discrete neutral molecular species that are solids at ambient temperatures, and where the cocrystal is a structurally homogeneous crystalline material that contains the building blocks in definite stoichiometric amounts [12],... 

In the context of organic synthesis, the term synthon was introduced by Corey in 1967 to refer to structural units within molecules which can be formed and/or assembled by known or conceivable synthetic operations. This general definition was modified by Desiraju for supramolecular chemistry Supramolecular synthons are structural units within supermolcules which can be formed and/or... 

Definition 2.3 The reaction distance D(S(/1), S (T)) between two synthons S(4) and S 04) is equal to the graph (topological) distance between those vertices that are assigned to them in %d A). 

Definition 2.4 A stable neighborhood of the synthon S(A), denoted by S(S(A)), is a set composed of stable synthons S (A) such that the internal vertices from each path of (S(A), S (A)) correspond merely to unstable synthons. 

Definition 2.5 A stable synthon S (A) is called synthon precursor successor (SPS) of the stable synthon S(A) iff the reaction graph GR of the transformation S(A) => S (A) is of a cyclic or linear form, see Fig. 12. Both forms must have alternating evaluation of edges by +/— and the linear graph must have terminal virtual vertices. The set of all possible SPS of the synthon S(A) is denoted by S(S(A)). 

Fig. 13. Schematic illustration of definition 2.6. In the first row a chemical transformation is displayed in which a synthon with two nonincident vertices from the reaction set X is transformed into another synthon with already incident vertices which were initially nonincident. In the second row a possible reaction graph is displayed...

Fig. 14. Schematic representation of single terms used in definition 2.7. Synthon S (/4) s <3(S(A/XIX)) is different from the synthon S(A) only in the upper block containing the vertices from A X. The bottom blocks represent the subsynthon S(X) and S (X), respectively, which are mutually isomorphic. In other words, the subsynthons S(X) and S (X) remain intact during the transformation S(A) => S (A)...

The synthon S(A) over an atomic set A is defined as one or several molecules (or their parts) composed of atoms from the set A. In contrast to the definition of the Ensemble of Molecules, EM (A) [13], S(A) is more general because it may also involve free valences, i.e. bonds which do not connect two atoms but only start from an atom. The set of all synthons constructed over the atomic set A is called the Family of Isomeric Synthons and is denoted FIS(A). Implicitly, it means... 

In previous sections almost all the basic algorithms of the synthon model of organic chemistry were briefly sketched. In this subsection we will present a more rigorous and detailed definition of the key algorithms, as the exact definition is needed for deep understanding of the possibilities, and limitations, of the synthon model. 

Molecular modelling is perhaps one of the most useful techniques available to chemists interested in designing supramolecular synthons or modifying their properties. However, despite the astounding advances in computational power and improvements in software over the past few decades, it must be stated first and foremost that results of computer-generated simulations are no substitute for laboratory-based experimentation. It is worth noting the primary dictionary definition of simulation is to assume the outward qualities or appearance of (something), usually with the intent to deceive [1] Computational approaches can be used to simulate atomic, molecular and supramolecular behaviour thereby... 

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