Organic moiety

In comparison to the Si—OR bond, the Si—C bond can be considered essentially unreactive if the organic moiety is a simple unsubstituted hydrocarbon. If the organic moiety is substituted as in the case of a trialkoxysilane, the chemistry is more appropriately considered elsewhere (see Silicon COMPOUNDS, SILANES SILICON COMPOUNDS, SILYLATING AGENTS). 

It is possible to react an organic moiety to the hydroxyl groups on ceU waU components. This type of treatment also bulks the ceU with a permanently bonded chemical (68). Many compounds modify wood chemically. The best results are obtained by the hydroxyl groups of wood reacting under neutral or mildly alkaline conditions below 120°C. The chemical system used should be simple and must be capable of swelling the wood stmcture to facUitate penetration. The complete molecule must react quickly with wood components to yield stable chemical bonds while the treated wood retains the desirable properties of untreated wood. Anhydrides, epoxides, and isocyanates have ASE values of 60—75% at chemical weight gains of 20—30%. 

R is an organic moiety, which can be aliphatic or aromatic. Most commonly used in adhesives are the aromatic isocyanates, e.g., methylene diphenylisocyanate (MDI) and toluene diisocyanate (TDI). These polyisocyanates and others will be discussed in Section 3. 

Eacli of tlie four organic moieties bridges between an equatorial and an axial copper atom tlirougli its C( 1) atom, while tlie nitrogen atom in tlie substituent is coordinated to an adjacent equatorial copper atom. Hie two bromine atoms bridge, at opposite sites, between two equatorial copper atoms. Tliis structural ariange-menl has tlie consequence tliat tlie aggregate incorporates two distinct types of... 

Y = RS", RCOO, or RO" (where R is a hydrocarbon residue or an organic moiety containing one or more heteroatom functionalities). 

The polymeric resin beads fill a need that arises from the instability of silica gel and its products to mobile phases of extreme pH (outside a pH range of about 4.0-7.0) and, consequently, are employed in most ion exchange separations. Organic moieties containing ionic groups can be bonded to silica and produce an effective ion exchange media, but the restrictions of pH on phase stability still apply. It follows that ion exchange bonded phases are less popular than the polymer bead alternatives. 

The brush phases are made from the mono-chlorsilanes or the mono-alkoxysilanes which attach a single organic moiety to each reacted hydroxyl group. For example using octyldimethylchlorsilane, dimethyloctyl chains would be attached to the surface like bristles of a brush, hence the term brush phase. In all bonding processes, some hydroxyl groups remain unreacted which would allow the polar character of the silica play a part in retention and also render the surface liable to dissolution in water and dilute acids. For this reason the material is capped by treatment with either trimethylchlorsilane or hexamethyldisilazane to eliminate any unreacted or stearically... 

In addition to complex-formation, the interaction of transition-metal atoms with organic substrates at low temperatures can result in rearrangement of the organic moiety without complexation. Two such reactions have already been briefly mentioned, namely, the polymerization of hexafluoro-2-butyne by Ge and Sn atoms (72) and the polymerization of styrene by Cr atoms (i 1). In this section we shall briefly summarize some of these transition-metal-atom-promoted, organic rearrangements. 

When a transition-metal hydride reacts with EtZnCl the organic moiety, rather than the halogen, is replaced ... 

Based on the molecular design of precursor metal complexes, the solvent-free controlled thermolysis of metal complexes may cause the thermal reduction and simultaneous attachment of organic moiety on the growing metal nuclei and give us a solution of the defects of ordinary... 

Result The sonochemical degradation of phenol is less than either p-aminophe-nol or p-nitrophenol. However, the sonochemical degradation of p-aminophenol is more than that of p-nitrophenol. This difference in the degradability of individual organic moieties can be understood / explained as below. 

At the end of this section, carbolithiation-based domino processes will be discussed in which a bond and a new lithium organic moiety from an alkene and a starting lithium compound is produced. The new lithium compound can react with another C-C-double or -triple bond and finally with an electrophile, as depicted in Scheme 2.121 [283],... 

Metal cations Organic moieties covalently attached to phyllosilicate framework References... 

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