Simple Multicomponent Compounds

Generally the most important components of a compound are the polymers, which supply much of the basic necessary properties ranging from mechanical behavior to solvent resistance. In this section we consider the simplest manner, in which the additional components may modify the properties of the neat polymers. 

We first consider that the simplest of multicomponent compounds consists of polymer components, which are mutually miscible. The particles of the filler are large, spherical, and interact only hydrodynamically. The oils should dissolve in the miscible polymer blend. The additives do not interact with each other and dissolve in the polymer blend-oil system. 

The viscosity enhancement of large particle (75 pm) filled compounds depends on the volume fraction of solid particles and particle shape. For roughly spherical large particles 

The modulus of the solidified product G((p) (or E((p)) will similarly be given by 

---

Liquid-Solution Models. The simple-solution model has been used most extensively to describe the dependence of the excess integral molar Gibbs energy, Gxs, on temperature and composition in binary (142-144, 149-155), quasi binary (156-160), ternary (156, 160-174), and quaternary (175-181) compound-semiconductor phase diagram calculations. For a simple multicomponent system, the excess integral molar Gibbs energy of solution is expressed by... 

Multicomponent compounds can accommodate many more types of defects than simple binary compounds. As we have seen, there are six types of point defects possible in binary compounds. In a ternary compound of general formula ML X, where L may represent a second type of electropositive component and r is the stoichiometric ratio of L to M (e.g., in MgAl204, M = Mg, L = Al, X = O, r = 2, and s = 4) the following point defects may occur V, Fl, V, M, L, Xj, X, Xl, Ml, M, and Lx, for a total of 12. Furthermore, in many ternary compounds (e.g., spinels) there are two types of interstitial sites, which adds three more possible defects. 

A simple example of the analysis of multicomponent systems will suffice for the present consideration, such as the calculation of the components in a gaseous mixture of oxygen, hydrogen and sulphur. As a first step, the Gibbs energy of formation of each potential compound, e.g. S2, H2S, SO, SO2, H2O etc. can be used to calculate the equilibrium constant for the formation of each compound from the atomic species of the elements. The total number of atoms of each element will therefore be distributed in the equilibrium mixture in proportion to these constants. Thus for hydrogen with a starting number of atoms and the final number of each species... 

In extending this concept to transformations that formally deliver Diels-Alder products, a one-pot three-component Mannich/Michael reaction pathway was developed in which simple cyclic enones, formaldehyde, and aryl amines were treated with catalytic amounts of proline (2) to provide regio-, diastereo-, and enantioselective bicyclic compounds in high yields (Scheme ll.lOb). Multicomponent domino... 

Heterocycles with a l,2,3,4-tetrahydropyrrolo[l,2-a]pyrazine core are also available through this multicomponent reaction. Compounds with a related structure are of high interest either for synthetic applications or for biological purposes. For the first time we were able to propose a one-pot access to pyrrolopiperazine and azasteroide-type scaffolds, illustrating the potential of this ecocompatible sequence to create molecular complexity and diversity from simple and readily available substrates (Scheme 60) [164]. In this case, the primary amine partner bears a pyrrole nucleophile, which neutralizes the transient iminium intermediate to form a new C-C bond via an intramolecular Pictet-Spengler-type cyclization. 

A general way to improve synthetic efficiency, which in addition also gives access to a multitude of diversified molecules in solution, is the development of multi-component domino reactions which allow the formation of complex compounds starting from simple substrates. Domino reactions are defined as processes of two or more bond-forming reactions under identical conditions, in which the subsequent transformation takes place at the functionalities obtained in the former transformation thus, it is a time-resolved process [la,c,f,3]. The quality and importance of a domino reaction can be correlated to the number of bonds formed in such a process and the increase of complexity. Such reactions can be carried out as a single-, two- or multicomponent transformation. Thus, most of the known multicomponent transformations [4], but not all, can be defined as a subgroup of domino transformations. 

An excellent introduction to the common features observed in electron spectra of non metallic surfaces and a simple discussion of the physical processes giving rise to these features is included in the review article by Holm and Storp (7). A good discussion from a practical introductory viewpoint is included in a Handbook of XPS (22). More exotic effects that lead to secondary lines of lower intensity such as multicomponent structure are more often encountered in transition metals and metallic oxides or transition compounds. These effects are discussed in more detail in Carlson (3) and Wertheim (23). 

This simple sketch illustrates clearly that convergent multicomponent reactions performed with a limited set of reactive building blocks (reactophores) in a multigeneration format offer a tremendous potential to produce diverse small-molecule compound collections, depending on the reaction sequence used (the combinatorics of reactive building blocks ). The concept of combinatorics of reactive building blocks should ultimately lead to novel multicomponent reactions. In Section III we will focus on reactophores such as a-alkynyl ketones, which allow the construction of a wide variety of core structures. 

Molecular fluorescence spectrometry has long been regarded as a useful technique for the determination of polycyclic aromatic hydrocarbons (PAHs) and related materials, due to the very high sensitivities which can be achieved. However, molecular fluorescence spectra measured in liquid solution usually are broad and relatively featureless hence, spectral interferences are common in the liquid-solution fluorometric analysis of multicomponent samples. Moreover, the fluorescence of a particular component of a complex sample may be partially quenched by other sample constituents if quenching occurs to a significant extent, the fluorescence signal observed for a particular compound present at a particular concentration will also depend upon the identities and concentrations of other substances present in the sample. Under these conditions, it is virtually impossible to obtain accurate quantitative results. Therefore, it is generally observed that molecular fluorescence spectrometry in liquid solution media is useful for quantitative determination of individual components in complex samples only if the fluorescence measurement is preceded by extensive separation steps (ideally to produce individual pure compounds or, at worst, simple two- or three-component mixtures). 

The parallel synthesis of several tens of compounds with two complementary SP routes employing a multicomponent reaction and producing diverse tetrahydroquinolines as decorated, biologically relevant scaffolds (101-103) was realized using simple laboratory equipment and commercially available reagents as monomers. The assessment work to produce compounds 6.14 and 6.25 with the optimized reaction conditions was deemed to be sufficientiy robust to pass immediately to library production. This... 

---