Pattern of substitution

The isothiazole ring causes deactivation of phenyl substituents, particularly in 3-phenyl-isothiazoles. Nitration of arylisothiazoles, however, occurs only in the benzene ring, the pattern of substitution varying greatly with the position of the aryl group on the isothiazole... 

The reactions of copper salts with diacyl peroxides have been investigated quite thoroughly, and the mechanistic studies indicate that both radicals and carbocations are involved as intermediates. The radicals are oxidized to carbocations by Cu(II), and the final products can be recognized as having arisen from carbocations because characteristic patterns of substitution, elimination, and rearrangement can be discerned " ... 

Metal alkyl reacts with nonsaturated ends of macromolecules following the pattern of substitution reaction [and causing a decrease in the number of methyl groups] ... 

The reactivity of diphenyl (6, X=H) and dibenzoy] (7, X=H) disulfide derivatives is higher than aliphatic derivatives. The value of Ctr depends markedly on the substituents, X, and on the pattern of substitution. Electron withdrawing substituents (e.g. X = p-CU or /t-NCK) may increase Cir by an order of magnitude.59 60 However, these compounds also give marked retardation. 

In contrast to AGX, the GAX consists of an arabinoxylan backbone, which contains about ten times fewer uronic acid side chains than a-L-Ara/ ones, and has some Xylp residues doubly substituted with these sugars. GAX are located in the non-endospermic tissues of cereal grains such as in wheat, corn, and rice bran. The degree and pattern of substitution of GAX appears to vary with the source from which they are extracted. These differences are reflected in the ratio of Ara to Xyl, the content of MeGlcA, and the presence... 

Of eleven possible triazaadamantanes from 76 to 86, only two, 1,3,5- with three nitrogens all at the bridegheads (76) and 2,4,8-triazaadamantanes with three nitrogens all at the bridges (77) are known. Interestingly, this pattern of substitution is similar to that in diazaadamantanes. 

The UV spectra of bisannelated benzenes are dependent on the pattern of substitution (Table H),66<=-68a,80,i09,iio annelations (meta) cluster around... 

As a consequence, the general pattern of substitutive names becomes ... 

Thiadiazoles are generally quite stable to heat due to the aromatic nature of the ring. Their thermal stability is influenced by the nature of the 3- and 5-substituents <65AHC(5)l 19>. Mass spectral decomposition patterns of substituted 1,2,4-thiadiazoles are discussed in Section 4.08.3.5. Photochemical behavior of 1,2,4-thiadiazoles has not been studied to date. 

FIGURE 15.2 Flavanones with simple patterns of substitution. 

The amount of substitution, and tendencies in the pattern of substitution, of galactomannans can be related to possible effects in the biosynthesis.116... 

For any one of the DHAP aldolases, the absolute configuration at the newly created stereocenter at C-3 is invariably conserved upon reaction with any electrophile, apparently for mechanistic reasons [199] no exceptions are known so far. For the stereogenic center at C-4, the relative positioning of the aldehyde carbonyl in the transition state, and thus the relative configuration in the product, usually follows closely that of the natural substrates. Depending on the nature of the enzyme used and on the pattern of substitution present in the aldehydic component, a distinct fraction of the 4-epimeric diastereomers may also be observed which is presumably the result of incorrect binding of the respective aldehyde (cf. Sect. 3.1). 

Consider chemistry. What are isoquinolines These are chemical structures built around a two-ring compound. This compound, Isoquinoline, consists of a benzene ring and pyridine ring fused together at a specific bond. There is a pattern of substitution that gives an isoquinoline its absolute definition. Thus, for example, Salsoline is an isoquinoline, which is a major component of the Pachycereus pecten-aboriginum plant. 

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