Examples of Chemical Structures

Japaa In Japanese Food Law, synthetic and naturally occurring additives are treated differently. The latter, in particular naturally occurring flavors and vitamins, do not require any special permission for use. The Japanese Ministry of Health and Welfare (MHW) is responsible for the approval of color additives which are outlined in a positive list of approved colors. MHW allows petitions for the addition of a new colorant to the list. Synthetic dyes permitted for food coloring in Japan include food dyes approved in the EU or/and in the USA (Table 5.7). 

A brief survey is given here of the chemical structure of some food dyes that have been approved for food coloration. From the chemical viewpoint several of the most frequently used synthetic food dyes belong to the azo series. 

1 In the Swiss List of Toxic Substances (Giftliste 1) the dye is classified as Toxic Cat. 4 (May 31, 1999). 

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Carbonyl pigments of a variety of types may also be classed as high-performance products. These include some anthraquinones, quinac-ridones, perylenes, perinones, isoindolines and diketopyrrolopyrroles. The chemistry of these groups of colorant is discussed in Chapter 4. Some representative examples of chemical structures of important high-performance carbonyl pigments are illustrated in Figure 9.4. 

Fig. 14. Examples of chemical structures of PCBs as cited in the text...

Figure 2.3 Example of chemical structure of a chlorogenic acid 5-O-caffeoylquinic acid (with ITJPAC numbering).

Figure 5.1 Some examples of chemical structures of common pesticides.

Table 6.10 gives examples of functionalized monomers and their applications. Examples of chemical structures are given in Figures 6.22-6.27. 

In a molecular system which clearly possess a ct LUMO the photoexcitation process may involve promotion of an electron from a n HOMO to the ct LUMO. This process may or may not produce bond cleavage. Direct observation of a 7t — ct electronic transition is often difficult due to the localized nature of the ct molecular orbitals resulting in a low probability for the transition [91]. More likely ait->it electronic transition takes place initially and ET, i.e., a - ct, is required to eventually populate the lower energy ct antibonding molecular orbital. Onium salts are examples of chemical structures that possess a ct LUMO and are expected to behave in this manner (see in Sect. 3.3). 

Figure 4.8-1 Electronic structure and chemical structure of hole and electron polarons (a), hole and electron bipolarons (b), and hole and electron solitons (c). Examples of chemical structures refer to poly(thiophene) and poly(acetylene), respectively.

Figure 1.11 Examples of chemical structures corresponding to the same GWB reduced graph of type R/F (shown in center). (Adapted from ref 224.)...

Eicosanoids, also referred to as icosanoids, are so named because of the 20-carbon constituency that identifies this class of oxygenated lipid molecules. A primary synthetic pathway for these molecules involves the phospholipase-mediated cleavage of a membrane phospholipid to produce arachidonic acid [(all-Z)-ik osa-5,8,ll,14-tetraenoic acid]. From this biologically essential intermediate fatty acid, two major subclasses of eicosanoids can be produced 1) leukotrienes, via the action of lipooxygenases, and 2) prostanoids, via the action of cyclooxygenases (COX-1 and COX-2). Examples of chemical structures for a leukotriene (Fig. la) and three types of prostanoids (Fig. Ib-d) underscore their shared arachidonate origin. 

Optical brighteners are usually derivatives of coumarin, stilbene, dis-tyrylbipheny, and bis(benzoxazole). Examples of chemical structures of some important optical brighteners are given ... 

FIGURE 1 Example of chemical structures of important degenerate and nondegenerate conjugated polymers. 

Scheme 3 Examples of chemical structures of hydrogenolysis of lignin...

Figure 4.3.3 Example of chemical structures of two basic dyes.

As an example of chemical structure and torsional angles, a sketch of a 1,4-poly butadiene chain in the planar all-trans conformation is shown in Figure 6. Rotational angles about bonds of the chain skeleton are measured relative to the planar conformation shown, for which (j)=0°. X-Ray diffraction studies on cis- and trans-polybutadiene indicate that CH2-CH2 bonds such as bond (i-l-2) connecting C,+i and Cj+2 in Figure 6 assume the trans conformation in the crystalline state. The rotational states accessible to these bonds in the amorphous state or in solution are concluded... 

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