Anionic ends structures

Influence of the Anionic Ends Structures In adding different monomer units at the end of monocarban-ionic polystyrenes, we obtain a set of carbanionic structures which habe been deactivated In the same way. The results (Table VI) show that the terminal unit, which allows the more delocalized anion or radical charge, and presents the more sterlc hindrance, gives the lower coupling ratio, and the best functionality. 

Influence of the Anionic Ends Structures on the Coupling Reaction and on the Functionality... 

Salts and Esters of Acids. Neutral salts of acids are named by citing the cation(s) and then the anion, whose ending is changed from -oic to -oate or from -ic to -ate. When different acidic residues are present in one structure, prefixes are formed by changing the anion ending -ate to -ato- or -ide to -ido-. The prefix carboxylato- denotes the ionic group —COO-. The phrase (metal) salt of (the acid) is permissible when the carboxyl groups are not all named as affixes. 

Polar solvents are those liquids whose relative permittivity is sufficiently high that electrolytes can be dissolved in them. The best-known example of such a liquid is water. The oxygen end of this simple molecule is electron-rich and can stabilize cations. The hydrogen atoms are electron-poor and thus are involved in the solvation of anions. The structure of pure water is very much influenced by the... 

The atomic arrangement of apatite sensu stricto is formed of three cation polyhedra, and the structural variations among the three anion end-members is perhaps best understood by examining variations that occur in the three polyhedra concomitant with substitution of the three column anions. The three polyhedra as they occur in fluorapatite, hydroxylapatite, and chlorapatite are compared and superimposed below. 

Ca2, in the 6h special position of space group P63//W, bonds to 6 oxygen atoms (01, 02, 4 x 03) and one column anion (X). The major structural response to substitution of the three column anions occurs in this polyhedron. Figure 1 displays the superposition of the three Ca2 polyhedra for the pure anion end-members, and illustrates the large shifts that occur in the positions of the X anions in the [OOz] anion column. 

As mentioned before, small cations also coordinate anionic end-groups, which means that such cations may exhibit different multidirectional behavior in a structure. Thus, the frequency of end-groups (lb)X is a function of the concentration of such cations. Complex cations like [M60] (M = Ca, Sr, Ba), which have also been found in Zintl phases, tend to act similarly. If the Zintl anions are viewed as soft geometrical sensors, then the coulomb fields generated by the complex cations should be similar to those of the above-discussed small or highly charged cations. 

The effect of chain-end structure (stability and steric requirements) has also been investigated. The steric and electronic nature of the anionic chain end can be modified by reaction with DPE as shown in eqn [17]. When the direct... 

The resins are based on standard styrene/divinyl benzene polymers with weakly acidic functionality. The first resins developed borrowed directly from chelation (L. chela = claw) chemistry. Compounds such as ethylene diamine tetraacetic acid (EDTA) when ionized have two monovalent anionic end groups that do in fact have a claw-like structure. They have a powerful affinity for divalent cations such as calcium and magnesium. When iminodiacetate functionality is built into a polymer, it provides... 

Stupp and coworkers reported on rod-coil systems containing a monodisperse rod part basing on an azo dye bound to a rigid monomer [151-153]. For these systems, the authors synthesized poly-isoprenes anionically and terminated the living chains with carbon dioxide resulting in carboxylated polyisoprenes that were then coupled to the rigid block (see Figure 42(a) for the end structure). 

POLYMER AND CHAIN END STRUCTURE IN ANIONIC DIENE POLYMERIZATION... 

In order to optimize specific anionic functionalization reactions such as carbonation with carbon dioxide, the effect of chain end structure (stability and steric requirements) has often been investigated. The steric and electronic nature of the anionic chain end and the chain-end aggregation can be modified by reaction with 1,1-diphenylethylene as shown in Eq. (13). When the direct carbonation is effected in benzene at room temperature with the diphe-nylalkyllithium species formed by addition of poly(styryl)lithium to 1,1-diphenylethylene (Eq. 31), the carboxylated polymer can be isolated in 98% yield compared to only a 47% yield for poly(styryl)lithium without end-capping under the same conditions [141] ... 

Conversion of Aromatic Rings to Nonaromatic Cyclic Structures. On treatment with oxidants such as chlorine, hypochlorite anion, chlorine dioxide, oxygen, hydrogen peroxide, and peroxy acids, the aromatic nuclei in lignin typically ate converted to o- and -quinoid stmctures and oxinane derivatives of quinols. Because of thein relatively high reactivity, these stmctures often appear as transient intermediates rather than as end products. Further reactions of the intermediates lead to the formation of catechol, hydroquinone, and mono- and dicarboxyhc acids. 

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