Bonding agents function

Systematic description of reductions of bonds and functions is preceded by discussion of methods, mechanisms, stereochemistry and scopes of reducing agents. Correlation tables (p. 177) show what reagents are suitable for conversion of individual types of compound to their reduction products. More... 

The hydroboration of carbon-carbon double bonds with diborane leads conveniently to trialkylboranes. The presence of second unhindered double or triple bonds, or functional groups generally affords a complicated mixture of products when diborane is employed as hydroborating agent, arising from competing hydroboration Chart 2). 

One of the most convenient synthetic routes for the preparation of vinyl fluorides 2 is by treatment of the corresponding vinyltin compounds 1 with electrophilic fluorinating reagents. This procedure is also used for the preparation of aryl fluorides, since it is well-established that fluorination with electrophilic reagents is facilitated by ipso substitution of a suitable, usually weakly bonded, metal function. In the case of aryl fluorides, the reaction is also carried out using elemental fluorine as the fluorinating agent. ... 

Surface silanols could react with many different functional groups to form the so-called bonded phase. The majority of the bonding agents used are chlorosi-lanes, although ethoxysilanes and sometimes alcohols are also used. Practically all commercially available chromatographic phases are made using silaniza-tion modification process. 

Lignin is an important component of wood, which functions primarily as an interfiber bonding agent. It is a three-dimensional, cross-linked polymer of heterogeneous structure composed of predominantly n-propylbenzene units joined by a variety of ether (C-O-C) and carbon-carbon (C-C) links (Fig. 15.3). Lignin is also biosynthetically derived from glucose, like cellulose. 

A third topic, not specific to the use of dioxygen as oxidizing agent, concerns selectivity and, in particular, the closely related aspect of over-oxidation. This problem is most severe in the partial oxidation of saturated hydrocarbons, because activation of alkanes is usually more difficult than that of any of the oxygenated products (e.g., alcohols and aldehydes), which are easily oxidized further. The reason is simply that C-H bonds of functionalized alkanes are generally weaker than those of the parent hydrocarbons. Moreover, as far as metal catalysis is concerned, the polar oxidation products can... 

Another intramolecular Heck reaction could be called a heteroaryl Heck reaction because the C-C bond formation involves a benzene and an indole ring. The resulting phenylcarbazoles are potential anti-cancer agents functioning as DNA topoisomerase I inhibitors. 

In addition to the blend of monomers, composite resins contain fillers. These are typically finely divided quartz or barium silicate glasses, and their function is to provide strength for the fully formulated composite [2]. These fillers are linked to the polymer phase by coupling agents, which are typically silane-based substances [2]. Composite reins are characterized by the absence of a chemical reaction between the filler and the monomer or polymer phase. Also, they show no inherent adhesion to the tooth but instead they have to be bonded to the tooth with bespoke bonding agents. These are discussed in detail in Chapter 5. 

---