Reactions and Compounds of Practical Importance

Both sodium and potassium are rather abundant in the Earth s surface (Na, 2.6% K, 2.4%), but potassium, due to its greater solubility and subsequent uptake by plant life, is much less prevalent in the seas. Indeed, potassium is so vital to plants that its major use, usually as the chloride or sulfate, is in fertilizers. This is certainly not a newly recognized technology. Even centuries ago, farmers knew that spreading wood ashes on their lands made crops grow better. We now recognize that the potassium in these ashes was primarily responsible for the effect. Both sodium and potassium ions are present in plants and animals and are essential for normal biochemical functions, particularly for the maintenance of the concentrations of ions across various cellular membranes, enzyme functions, and the firing of nerve impulses. 

Advertisement for 7-Up, the lithiated lemon soda. 7-Up contained lithium citrate between 1929 and 1950. Its advertising slogan was takes the ouch out of grouch.  

Other applications of these elements take advantage of their nuclear properties. For example, one prevalent method of establishing the age of early humanoids is the potassium-argon dating procedure developed in the 1950s. Potassium-40 has a half-life of 1.3 billion years and decays by either beta-minus or beta-plus emission, as shown in Equations (12.22) and (12.23)  

Other uses of the alkali metals related to their nuclear properties include the use of lithium-6 and lithium-7 in nuclear reactors to produce tritium, as shown in Equations (12.24) and (12.25)  

Tritium would then be readily available for use in fusion reactors. (See Chapter 10, p. 273, for more details on fusion as an alternative energy source of the future.) 

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The first two sections of this chapter are the usual ones on (1) the discovery and isolation of the elements and (2) the application of the network to group chemistry. The third section, necessitated by the great ability of sulfur to catenate, concentrates on the allotropes and compounds that involve element-to-element bonds. Next is a short section on the relatively new and potentially useful sulfur nitrides. The reactions and compounds of practical importance in the fourth section include sodium-sulfur batteries, the photoelectric properties of selenium and tellurium, and the most important commercial chemical in the world, sulfuric acid. The selected topic in depth is the production, effects, and possible control of acid rain. 

After the usual sections on the history of the discoveries of and the application of the network to the halogens, special sections on (1) the oxoacids and their salts and (2) the interhalogens follow. The section on reactions and compounds of practical importance comes next and finally the selected topic in depth, which concerns the threat posed by chlorofluorocarbons to the ozone layer. 

Usually at this point, we discuss reactions and compounds of practical importance. However, for Group 8A there are very few reactions and compounds of any kind, independent of their practical importance. On the other hand, there are, to use the... 

At present nitration is one of the most widely applied direct substitution reactions. This is due to several factors. For example nitration usually proceeds easily, its products can readily be separated from the spent acid, said there is a wide range of possibilities in the practical use of nitro compounds, both as intermediates and end products. The presence of a nitro group in the starting product made it possible to obtain a number of basic organic intermediates such as aniline said benzidine. Dyes with more than one nitro group, such as picric acid were obtained. It has been found that higher nitrated nitro compounds and nitric acid esters have explosive properties and are of practical importance. Some nitro compounds are used in perfumes. Medicinal properties have lately been discovered in certain nitro compounds, eg. chloramphenicol. 

The reaction is of practical importance in the vulcanization of siUcone mbbers (see Rubber compounding). Linear hydroxy-terrninated polydimethyl siloxanes are conveniently cross-linked by reaction with methyldiethoxysilane or triethoxysilane [998-30-1]. Catalysts are amines, carboxyflc acid salts of divalent metals such as Zn, Sn, Pb, Fe, Ba, and Ca, and organotin compounds. Hydroxy-terrninated polysiloxanes react with Si—H-containing polysiloxanes to... 

A large fraction of the chemical reactions known are used to form heterocyclic compounds. Displacement reactions and cycloadditions are particularly important, and their rates are therefore of great practical interest. The same is true for the rates of reverse reactions — ring opening by displacements or retrocycloadditions. It was realized over the last 40 years that... 

Exercise 13-17 Show how each of the following compounds could be synthesized from the indicated starting material and other appropriate organic or inorganic reagents. Specify the reaction conditions, mention important side reactions, and justify the practicality of any isomer separations. 

Modified polyphosphate pigments, which are of practical importance today, are predominantly reaction products of acidic aluminum tripolyphosphate with compounds based upon zinc, strontium, calcium, and magnesium (Table 5.7). 

One of the characteristic features of aromatic nitro compounds, particularly those with two or more nitro groups is their ability to react with bases and in many instances the reaction is accompanied by an intense colour. The colour had caught the attention of chemists by the late nineteenth century and initiated a considerable amount of research on the nature of the formed substances. Thus considerable literature appeared on reactions known as Janovsky or Jackson-Meisenheimer or Meisenheimer reactions which are discussed later. They are nucleophilic reactions and are not only of theoretical but also of practical importance. Thus the Janovsky reaction became an important analytical method, and reactions of di- and trinitrobenzene and their homologues with bases, are of great importance in the problem of the safety of manufacture and of the stability of these nitro compounds. 

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