Chemical functional groups, role

Dendrimers are molecules with regularly placed branched repeat units. They are also known as Starburst, Cascade or Arborols. These names describe aspects of their molecular architecture. Dendrimers consist of different parts (see Fig. 1). Each dendrimer has a core or focal point. The core is the central unit of the den-drimer and can formally be regarded as the center of symmetry for the entire molecule. The core has its characteristic branching functionality, i.e. the number of chemical bond by which it is connected to the rest of the molecule (Fig. la). The focal point plays the same role as the core. Moreover,it has a chemical functional group not found elsewhere in the dendrimer. 

Zeolite membranes are amenable by surface modification with a variety of chemical functional groups using simple silane chemistry that may provide alternative surface chemistry pathways for enzyme immobilization. In this context, Shukla et al. [338] have recently used a chemically modified zeolite-clay composite membrane for the immobilization of porcine lipase using glutaraldehyde to provide a chemical linkage between the enzyme and the membrane. The effects of pH, temperature, and solvent on the performance of such biphasic zeolite-membrane reactors have been evaluated in the hydrolysis of olive oil to fatty acids. Similarly, Algieri et al. [339] have immobilized tyrosinase on FAU membranes for the enzymatic conversion of the 1-tyrosine to 1-DOPA as an effective drug for Parkinson s disease treatment. This approach combines the active role of zeolite membrane as enzyme support and inhibitor suppressor. Moreover,... 

Broadly, chemical functional groups, their overall charge, roughness and the wettability of a surface have fundamental roles in determining their favourability for cell attachment, spreading and proliferation [11,16,17]. 

Collectors ndFrothers. Collectors play a critical role ia flotation (41). These are heteropolar organic molecules characterized by a polar functional group that has a high affinity for the desired mineral, and a hydrocarbon group, usually a simple 2—18 carbon atom hydrocarbon chain, that imparts hydrophobicity to the minerals surface after the molecule has adsorbed. Most collectors are weak acids or bases or their salts, and are either ionic or neutral. The mode of iateraction between the functional group and the mineral surface may iavolve a chemical reaction, for example, chemisorption, or a physical iateraction such as electrostatic attraction. 

Thus, in spite of its lack of reactivity, iodine reacts chemically with unsaturated compounds, whereby the silica gel of the TLC layer can sometimes be assigned a catalytic role [11, 12]. Irreversible oxidations and electrophilic substitution and addition reactions have been observed on the interaction of iodine with tertiary nitrogen compounds such reactions possibly depend on particular steric relationships or are favored by particular functional groups [13, 14]. 

In characterizing the aims, methods, and values of chemistry, some chemists recently have stressed the irreducibility of chemistry to physics. Hoffmann, for instance, in reflecting on the question, has written that "most of the useful concepts of chemistry (for the chemist aromaticity, the concept of a functional group, steric effects, and strain) are imprecise. When reduced to physics they tend to disappear."40 Further, it is the very ambiguity of some chemical concepts, like "oxidation state," that appeals to chemists. For chemists, the oxidation state of an atom varies according to its role in a molecule, appearing to vary from, perhaps, + 3 to -2 for an atom. Physicists are uneasy with this "elastic" heuristic device.41... 

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