Structural Features of Solids

CHAPTER 12 Intermolecular Forces Liquids, Solids, and Phase Changes 

There are 7 erystal systems and 14 types of unit cells that occur in nature, but we will be eoneerned primarily with the cubic system, which gives rise to the eubic lattiee. The solid states of a majority of metallic elements, some covalent eompounds, and many ionic compounds occur as cubic lattices. (We also describe the hexagonal unit eell a bit later.) There are three types of cubic unit cells within the cubie system  

Atoms/unit cell = g x 8 = 1 Atoms/unit cell = (gx 8) + 1 =2 

Body-centered cubic unit cell. C, Face-centered cubic unit cell. 

Top row Cubic arrangements of atoms in expanded view. Second row Space-filling views of these cubic arrangements. All atoms are identical but. for clarity, corner atoms are blue, body-centered atoms pink, and face-centered atoms yellow. Third row A unit cell shaded 

Animation Cubic Unit Cells and Their Origins Online Learning Center 

The packing efficiency of both hexagonal and cubic closest packing is 74%, and the coordination number of both is 12. There is no way to pack identical spheres more efficiently. Most metallic elements crystallize in either of these arrangements. Magnesium, titanium, and zinc are some elements that adopt the hexagonal structure nickel, copper, and lead adopt the cubic structure, as do many 

---

Chatani, Y., Structural Features of Solid-State Polymerization, in Progress in Polymer Science Japan, Vol. 7, p. 149, K. Imahori and T. Higashimura, eds., Halsted Press (Wiley), New York, 1974. 

Structural Features of Solids Crystalline Solids Amorphous Solids Bonding in Solids... 

The Solid State Structure, Properties, and Bonding 373 Structural Features of Solids 373 Types and Properties of Crystalline Solids 379... 

Khaldoyanidi, 2003] K. A. Khaldoyanidi. Structural features of solid phases and topology of phase diagrams. Journal of Structural Chemistry 44 116-129, 2003. 

The practical development of plant sterol drugs as cholesterol-lowering agents will depend both on structural features of the sterols themselves and on the form of the administered agent. For example, the unsaturated sterol sitosterol is poorly absorbed in the human intestine, whereas sitostanol, the saturated analog, is almost totally unabsorbable. In addition, there is evidence that plant sterols administered in a soluble, micellar form (see page 261 for a description of micelles) are more effective in blocking cholesterol absorption than plant sterols administered in a solid, crystalline form. 

Incorporation into a Polymer Layer In recent years a new electrode type is investigated which represents a layer of conducting polymer (such as polyaniline) into which a metal catalyst is incorporated by chemical or electrochemical deposition. In some cases the specific catalytic activity of the platinum crystallites incorporated into the polymer layer was found to be higher than that of ordinary dispersed platinum, probably because of special structural features of the platinum crystallites produced within the polymer matrix. A variant of this approach is that of incorporating the disperse catalyst directly into the surface layer of a solid polymer electrolyte. 

In its solid state, however, the basic structural features of ordinary hexagonal ice (ice I) are well established. In this structure (Figure 1.2), each water molecule is hydrogen bonded to four others in nearly perfect tetrahedral coordination. This arrangement leads to an open lattice in which intermolecular cohesion is large. 

At this stage it could be useful to make a comment on the structural features of complexes 4-17. The coordination number of the metal affects strongly the shape of the calix[4]arene fragment. In the case of five-coordinate and, eventually, four-coordinate metals, the calix[4]arene moiety displays a cone, which changes to an elliptical conformation in the case of a six-coordinate metal.4,10 Such conformation changes, which appear in the solid state, are also detectable in solution, as in the... 

The epoxide selectivity did not depend noticeably on the gross structural features of the catalyst. For instance, the selectivity in the epoxidation of 4 is about 85% on all solids (Table XIII). 

Pores are found in many solids and the term porosity is often used quite arbitrarily to describe many different properties of such materials. Occasionally, it is used to indicate the mere presence of pores in a material, sometimes as a measure for the size of the pores, and often as a measure for the amount of pores present in a material. The latter is closest to its physical definition. The porosity of a material is defined as the ratio between the pore volume of a particle and its total volume (pore volume + volume of solid) [1]. A certain porosity is a common feature of most heterogeneous catalysts. The pores are either formed by voids between small aggregated particles (textural porosity) or they are intrinsic structural features of the materials (structural porosity). According to the IUPAC notation, porous materials are classified with respect to their sizes into three groups microporous, mesoporous, and macroporous materials [2], Microporous materials have pores with diameters < 2 nm, mesoporous materials have pore diameters between 2 and 50 nm, and macroporous materials have pore diameters > 50 nm. Nowadays, some authors use the term nanoporosity which, however, has no clear definition but is typically used in combination with nanotechnology and nanochemistry for materials with pore sizes in the nanometer range, i.e., 0.1 to 100 nm. Nanoporous could thus mean everything from microporous to macroporous. 

CH3CN (8 -85.1) and 32 CH3CN (8 -84.8) by the solid-state NMR experiments. Furthermore, the solution-state NMR data of 31 and 32 differ significantly from all the other 29Si chemical shifts listed in Table IV. These results are indicative of special structural features of the zwitterions 31 and... 

In this section, an example will be given in which a (small) library of a new type of cationic lipids was synthesized and screened for TE (63). For synthesis, combinatorial solid phase chemistry was used. All cationic lipids of the example library are structurally based on 3-methylamino-1,2-dihydroxy-propane as the polar, cationic lipid part. As nonpolar lipid part, different hydrocarbon chains are boimd to the amino group of the scaffold and the amino group was further methylated to get constantly cationic-charged lipids. Lipids were synthesized in both configurations and as racemats, and the counterions were varied as well. Table 1 summarizes the structural features of these lipids. 

The structural features of the linear R-Cu-R arrangement are identical to those observed for other [R2CU] anionic units discussed previously (cf. Fig. 1.31). The [Li2CN(THF)2(PMDTA)2] cationic unit consists of a central cyanide moiety, to which two lithium atoms are bound in end-on fashion. Coordination saturation at each lithium atom is achieved by coordination of the three nitrogen atoms of the PMDTA molecule and one THF molecule, rendering each lithium atom penta-coordinate. Recent H, Li HOESY experiments showed that this ionic structure found in the solid state is probably retained in polar solvents such as THF [140]. 

The HDAC inhibitors TSA and TPX (Fig. 2) have been utilized as structural leads in the early stages of the quest for new and more selective small molecule inhibitors of the HDAC enzyme family. In order to investigate the function of the individual HDAC members, Schreiber et al. synthesized a library of 7200 potential HDAC inhibitors based on the structural features of TSA and TPX [93]. The members of this library were prepared on solid support by means of split pool methods. The key characteristics of these compounds consist of a dioxane-containing capping region and a zinc binding motive, connected via an aliphatic chain. Three different zinc binders, i.e., carboxylic acid, o-aminoanilide and hydroxamic acid were used. 

---