Chemical versatility

The most important members of the cyanocarbon class are the alkenes tetracyanoethylene, hexacyanobutadiene, and tetracyanoquino dime than the alkanes tetracyanomethane and hexacyanoethane dicyano acetylene hexacyanobenzene tetracyanoquinone cyanocarbon acids oxacyanocarbons thiacyanocarbons and azacyanocarbons. Tetracyanoethylene is described first because its chemical versatility makes it a rich source of other polycyano compounds. Moreover, an understanding of its chemistry is helpful in understanding the chemistry of other cyanocarbons. 

Molybdenum because of its unique chemical versatility and unusually high bio-availability has been incorporated widely into biological systems. It is the only second-row transition metal that is essential for most of living organisms and belongs to elements (along with Cu, Cd, Hg, Pb and Cr) potentially hazardous to humans. 

The side chains of the 20 different amino acids listed in Panel 1.1 (pp. 6-7) have very different chemical properties and are utilized for a wide variety of biological functions. However, their chemical versatility is not unlimited, and for some functions metal atoms are more suitable and more efficient. Electron-transfer reactions are an important example. Fortunately the side chains of histidine, cysteine, aspartic acid, and glutamic acid are excellent metal ligands, and a fairly large number of proteins have recruited metal atoms as intrinsic parts of their structures among the frequently used metals are iron, zinc, magnesium, and calcium. Several metallo proteins are discussed in detail in later chapters and it suffices here to mention briefly a few examples of iron and zinc proteins. 

Butadiene is a diolefmic hydrocarbon with high potential in the chemical industry. In 1955, it was noticed that the assured future of butadiene (CH2=CH-CH=CH2) lies with synthetic rubber. . . the potential of butadiene is in its chemical versatility. .. its low cost, ready availability, and great activity tempt researchers. 

Solvent polymeric membranes, conventionally prepared from a polymer that is highly plasticized with lipophilic organic esters or ethers, are the scope of the present chapter. Such membranes commonly contain various constituents such as an ionophore (or ion carrier), a highly selective complexing agent, and ionic additives (ion exchangers and lipophilic salts). The variety and chemical versatility of the available membrane components allow one to tune the membrane properties, ensuring the desired analytical characteristics. 

To support the various spectroscopic methods for structure determination of dienes and polyenes we will mention some typical chemical reactions yielding derivatives that aid in the location of the double bonds, assign the cis or trans geometry and indicate whether these double bonds are conjugated. It is not our intention to review the chemical versatility of dienes and polyenes but rather to show some cases where the variation helps in the analysis. 

The chemical versatility of the oxaspiropentanes makes these compounds exceedingly useful building blocks. Being a strained epoxide, they are very labile towards acid catalyzed rearrangements accompanied by carbon bond migration leading to... 

The C4 family includes normal and iso butane, C4H10, which have only single bonds, normal and isobutylene butenes, C4HS, which each have one double bond and butadiene, C4H(5, which has two double bonds. The reactivities and chemical versatility of these three groups are roughly related to the number of double bonds. 

Epoxides are much more reactive than simple ethers due to ring strain, and are useful intermediates because of their chemical versatility. They undergo nucleophilic substitution reactions with both acids and bases to produce alcohols (see Sections 4.3.7 and 5.5.4). 

The redox properties of tris(quinoxaline-2,3-dithiolato)molybdate(IV), [Mo(qdt)3]2, in the presence of protons provides a clear demonstration of the chemical versatility that is possible for a redox-active metal dithiolene center that involves a pyrazine ring linked to the dithiolene group. In an aprotic solvent, two reversible, Nernstian, waves are observed that (formally) correspond to the Mo(V)/Mo(IV) and Mo(IV)/Mo(III) couples. However, on addition of trifluoroacetic acid (Htfa), the Mo(V)/Mo(IV) couple slightly shifts to a higher potential and becomes non-Nernstian and a new three-electron, quasir-eversible, couple occurs some 900 mV less negative than the original Mo(IV)/ Mo(HI) couple. The latter is attributed to the addition of one electron and one... 

By carefully designing the reaction sequence so that the first step creates the conditions to trigger the next stage, and that in turn sets up the third reaction, and so on, chemists can plan this type of multistage reaction. In this context, the choice of starting materials with high chemical versatility is crucial. 

The aim of this chapter is to show some representative examples in which aliphatic nitrocompounds are the key starting materials for the synthesis of different targets in a one-pot process. Thus, the availability of a variety of nitroalkenes and nitro-alkanes, their chemical versatility and their reactivity make these compounds highly powerful precursors and intermediates in environment-friendly organic synthesis. 

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