Unusual Examples

In the absence of a detailed mechanishc inveshgation, a few examples available in the literature are difficult to categorize according to the format used in this chapter. 

Formally, the affected monomers and obtained polymers match the definition of a cycloalkane direct ROP, but the known chemistry of the monomers or close analogues casts some doubts on the polymerization mechanism. Of specific concern are monomers known to rearrange into molecules whose polymerization becomes possible via an addition on a C=C double bond. A few examples are presented below  

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This space truss is seemingly an unusual example, but space is now a part of our everyday lives. Thus, there are many space examples in which you must expect to use composite materials because they are the least-expensive design solution. The raw material cost is not even close to the bottom-line cost. The raw material cost has something to do with the bottom line, but the ordering of material choices that you get based on raw material cost does not mean anything in comparison to the ordering of the actual bottom-line costs. 

In an unusual example of displacement of fluonne by hydroxyl, hydroxyl radicals attack fluorinated benzenes Hexafluorobenzene is the least reactive The hydroxyl radical generates the pentafluorocyclohexadienonyl radical from it [13] (equation 13) These unstable species are detected spectroscopically Their disap-... 

Fluorinated alkenes can insert into C-H bonds at elevated temperatures, a relatively unusual example of simultaneous C-C and C-H bond formation [20, 21] (equations 16 and 17)... 

Halide complexes are also well known but complexes with nitrogen-containing ligands are rare. An exception is the blue phthalocyanine complex formed by reaction of Be metal with phthalonitrile, 1,2-C6H4(CN)2, and this affords an unusual example of planar 4-coordinate Be (Fig. 5.5). The complex readily picks up two molecules of H2O to form an extremely stable dihydrate, perhaps by dislodging 2 adjacent Be-N bonds and forming 2 Be-O bonds at the preferred tetrahedral angle above and below the plane of the macrocycle. 

The complex CUCN.NH3 provides an unusual example of CN aeting as a bridging ligand at C, a mode which is common in p,-CO complexes (p. 928) indeed, the complex is unique in featuring tridentate CN groups which link the metal atoms into plane nets via the Cu... 

An unusual example involves two complexes of formula Au(S2CNBu2)-(S2C2(CN)2) one has a molecular structure, the other is ionic [Au(S2CNBu2)2]+[Au[S2C2(CN)2]2]- [133],... 

Deamination reactions of (2-amino-l,l-dimethyl)ethyldiphenylphosphine oxide (57) result in the formation of three products, in each of which the diphenylphosphinyl group has migrated to the primary carbon of the starting material. These reactions are unusual examples of non-assisted migration of a phosphinyl group. 

Heavy-metal cations and oxyanions are generally toxic to bacteria although resistance may be induced by various mechanisms after exposure. Attention is drawn to an unusual example in which AF+ may be significant, since the catechol 1,2-dioxygenase and 3,4-dihydroxybenzoate (protocat-echuate) 3,4-dioxygenase that are involved in the metabolism of benzoate by strains of Rhizobium trifolii are highly sensitive to inhibition by AP (Chen et al. 1985). 

An unusual example of a process that produces a lot of waste is the intensive rearing of pigs. They need additional phosphorus in their feed for healthy growth, and this is usually added as inorganic phosphorus in the form of monocalcium phosphate (calcium dihydroxy-oxido-oxo-phosphorane). Unabsorbed phosphorus passes through into the manure, and if spread onto fields as a fertiliser can lead to excess phosphorus run-off into rivers and lakes leading to eutrophication. 

An unusual example of an anchimerically assisted (O—C) bond cleavage is found in the electron impact induced dissociation of alkyl silylmethyl ether 137 (33) 6). 

Several nickel(II) complexes (e.g., (173)-(176)) have successfully been used to catalyze ATRP, especially when coupled with bromo-initiators, although activities are usually lower than with copper, ruthenium or iron systems.416-419 The alkylphosphine complex (175) is thermally more stable than (174) and has been used to polymerize a variety of acrylate monomers between 60 °C and 120 °C.418 Complex (176) is an unusual example of a well-defined zerovalent ATRP catalyst it displays similar activities to the Ni11 complexes, although molecular weight distributions (1.2-1.4) are higher.419 Pd(PPh3)4 has also been investigated and was reported to be less controlled than (176).420... 

Conversion of other heterocyclic systems into pyridazines has also been used, for example the reaction of 3-aminopyrone 9 with hydrazine, followed by oxidative aromatisation <06T9718> and the more unusual utilisation of a 1,2,4-triazole 10 as the source of the N-N unit <06T8966>. In this latter transformation, the intermediate quaternary salt 11 was isolable. An even more unusual example was the reaction of the diazetidine 12 with enolates <06S2885>. 

The theoretical lower limit of the molecular weight distribution for the diblock OBC is 1.58. The observed MJMn of 1.67 indicates that the sample contains a very large fraction of polymer chains with the anticipated diblock architecture. The estimated number of chains per zinc and hafnium are also indicative of a high level of CCTP. The Mn of the diblock product corresponds to just over two chains per zinc but 380 chains per hafnium. This copolymer also provides a highly unusual example of a polyolefin produced in a continuous process with a molecular weight distribution less than that expected for a polymer prepared with a single-site catalyst (in absence of chain shuttling). 

A conveniently prepared amorphous silica-supported titanium catalyst exhibits activity similar to that of Ti-substituted zeolites in the epoxidation of terminal linear and bulky alkenes such as cyclohexene (22) <00CC855>. An unusual example of copper-catalyzed epoxidation has also been reported, in which olefins are treated with substoichiometric amounts of soluble Cu(II) compounds in methylene chloride, using MCPBA as a terminal oxidant. Yields are variable, but can be quite high. For example, cis-stilbene 24 was epoxidized in 90% yield. In this case, a mixture of cis- and /rans-epoxides was obtained, suggesting a step-wise radical mechanism <00TL1013>. 

The charts are arranged in order of increasing element content. Correlations given in one chart (e.g. those for Cl I2 and CH3) are not repeated in subsequent charts. The frequency limits within which the band of a particular grouping is usually found are indicated by the black strips and extensions of the range to include unusual examples are shown as thin lines, e g. relative intensities are given in a very approximate fashion (see below). Both the position and the intensity of some absorptions are dependent on state, solvent, etc., and the actual frequency quoted is that most commonly observed. 

The opposite of the stabilisation of an ester is its activation. If we include in the concept ester the alkyl halides, their Friedel-Crafts reactions provide familiar examples of this phenomenon. An unusual example especially relevant to our present considerations is provided by some results made available to me in advance of publication by Giusti and Andruzzi. Their results [38] on the polymerisation of styrene by iodine and hydrogen iodide can be interpreted in terms of an organic iodide derived from styrene, probably 1-phenylethyl iodide, being activated by the co-ordination of one or two molecules of iodine. This process appears to polarise the C—I bond to such an extent that the normally stable ester becomes activated to a chain-propagating species and induces a pseudocationic polymerisation ... 

Unusual examples of the dienone-phenol rearrangement include the reactions of 1,4-dihydrosilabenzene 361 which rearranges in two directions upon treatment with BCI3 or during purification on silica gel (equation 131)185. 

The use of iron(II) sulfate as a detoxicant for mimosine-affected sheep is an unusual example of iron supplementation (7). It provides an interesting complement and link to the following paragraphs on the use of hydroxypyridinones as detoxicants for iron-burdened humans. 

Somewhat unusual examples, which illustrate the usefulness of cycloadditions in the synthesis of polycyclic compounds, are the controlled synthesis of an unsymmetrically substituted aromatic compound (131 from very simple commercially available compounds (Scheme 6.9), and the one-step thermal cyclisation of compound J6 to the aromatic steroid 14 (Scheme 6.10). 

One of the first examples of this type of blend was composed of SPEEK or SPES as the acidic component and diaminated PES, poly(4-vinylpyridine) (P4VP), poly(benzimidazole) (PBl), or poly(ethyleneimine) (PEI) as the basic component. " For blend lEC values of 1.0 meq/g, conductivity values were reported to be good, as was H2/O2 EC performance. Thermal stabilities for these blends was also demonstrated to be high (>270°C). Other examples of acid-base PEMs include blends of SPPO and PBI, sulfonated poly(phthalazinone ether ketone) and aminated SPES, SPIs and aminated Pls, and SPEEK with PES bearing benzimidazole side groups, ° as well as an unusual example in which the blend is composed of sulfonated, hyper-branched polyether and pyridine-functionalized polysulfone. ... 

Unusual example of bidentate ligand involved in linkage isomerism. Forms characterized by P nmr and x-ray diffraction. (ly isomer favored at 40 °C pH 6.5. No kinetic data on rearrangement. 

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