Main Chemical Classes

The ideal properties required from any class of organic photochromic compounds are 

Colour development. The material must develop rapidly a strong colour upon irradiation with UV light 

Control of return back to colourless state. The fade rate back to the colourless state must be controllable 

Wide colour range. The range of colours must be across the visible spectrum 

Long life. The response must be constant through many colouration cycles 

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Act to decompose hydroperoxides into stable molecules such as alcohols and ethers, before they can react with light to form free radicals. Main chemical classes are trivalent phosphorous compounds and thio-synergists (esters of thiodipropionic acid). Sulfur-based organic antioxidants decompose hydroperoxides by non-radical reactions. Typical peroxide decomposers are Irgafos 168, Ultranox 626, Irganox PS 800 and others. 

In the following sections we review the compositions of the main chemical classes and their biochemical functions. These functions are related to the structure and shape of the basic carbon skeleton of a molecule and the functional groups (see Box 2.1) attached to it. 

While sterically hindered phenols and secondary aromatic amines are the two main chemical classes of antioxidants for thermoplastics, the greatest diversity is, however, found in the class of the sterically hindered phenols. Most of these phenols are commercially available as relatively pure chemicals. Although aromatic amines are often more powerful antioxidants than phenols, their application is... 

Many synthetic polymers form cholesteric phases, and even solids showing certain of the fundamental symmetries of cholesteric liquids. The purpose of this paper is to review the main examples of biological polymers assembling into cholesteric liquids or into more or less solid analogues. We will present them according to the main chemical classes of polymers to which they belong. We will also indicate the main forces involved in creating the cholesteric twist. 

In order to illustrate the large variety of compounds used as pesticides, the main chemical classes belonging to fungicides and insecticides are listed in Table 6. 

There are three main chemical classes of TPUs polyester, polyether, and a smaller class known as polycaprolactone [3]. 

Abiotic reactions which lead to the formation of cell nutrients at ambient temperatures fall into two main chemical classes namely, hydrolysis and... 

It is also interesting to examine the distribution of the secondary metabolites by main chemical class terpenes... 

Vat Dyes. These water-iasoluble dyes ate appHed mainly to ceUulosic fibers as soluble leuco-salts after teductioa ia an alkaline bath, usuaUy with sodium hydrosulfite. FoUowiag exhaustion onto the fiber, the leuco forms ate reoxidized to the iasoluble keto forms and aftertreated, usuaUy by soapiag, to redevelop the crystal stmcture. The principal chemical classes of vat dyes ate anthraquiaone and iadigoid. 

Antifungal drugs are classified according to their mode of action and/or their chemical class. Four chemical classes have mainly contributed to the actual armentory of antifungal drugs the broadest class is the one of azoles (imidazoles and triazoles), followed by polyenes, allylamines and morpholines. Some individual compounds are used in dermatology. 

The chemistry of the three most important chemical classes of organic colorants, the azo, carbonyl and phthalocyanine classes, has been dealt with individually in Chapters 3-5 respectively. In this chapter, the chemistry of a further five chemical classes which are of some importance for specific applications is discussed. These classes are the polymethines, arylcarbonium ion colorants, dioxazines, sulfur dyes and nitro dyes. A section of this chapter is devoted to each of these, each individual section contains a description of the principal structural features which characterise the particular colorant type, together with an outline of the chemistry of the main synthetic routes. There are many other chemical types of dyes and pigments that do not fall into the categories previously mentioned, but which are neglected in this text either because they are commercially of little importance or because they have been less extensively investigated. 

In Chapters 3-6, the commercially important chemical classes of dyes and pigments are discussed in terms of their essential structural features and the principles of their synthesis. The reader will encounter further examples of these individual chemical classes of colorants throughout Chapters 7 10 which, as a complement to the content of the earlier chapters, deal with the chemistry of their application. Chapters 7, 8 and 10 are concerned essentially with the application of dyes, whereas Chapter 9 is devoted to pigments. The distinction between these two types of colorants has been made previously in Chapter 2. Dyes are used in the coloration of a wide range of substrates, including paper, leather and plastics, but by far their most important outlet is on textiles. Textile materials are used in a wide variety of products, including clothing of all types, curtains, upholstery and carpets. This chapter deals with the chemical principles of the main application classes of dyes that may be applied to textile fibres, except for reactive dyes, which are dealt with exclusively in Chapter 8. 

The aim in this chapter is to summarise the properties of auxiliaries normally used with each of the main dye classes. Where these agents have been dealt with earlier, the emphasis here is on application behaviour. Chemical details are included, however, for those auxiliaries that have not yet been mentioned emphasis is given to the auxiliaries used rather than to processing details. 

This small group of hydroxyquinone (1.16), arylaminoquinone (1.17) and aminophthalimide (1.18) derivatives has contributed a few members of some application ranges, mainly yellow disperse dyes and reddish brown vat dyes, but there are superior alternatives available from the major chemical classes. 

FBAs can be classified according to their application, e.g. in detergents, by far the major use, on paper, the second largest, or on a variety of textiles and plastics. Alternatively, they can be grouped according to their chemical class. In this book the latter will be used, together with an indication of the main application areas of the various major products. 

The inhalation anesthetics belong to diverse chemical classes. There main indication is the maintenance of anesthesia after intravenous induction. There are no suggestions that they interact with pharmacologically-defined receptors like some of the injectable anesthetics do and they have no specific site of action. Apparently they cause physical changes in cells such as changes in cell membrane fluidity. 

Main use Common/trade Chemical class/Structure Source ... 

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