Side substitution

Interesting examples are found in substituted anthracenes. The lifetimes and quantum yields of fluorescence of substituted anthracenes show different dependencies on temperature. The position of the substituent is more important than its nature. For 9- and 9,10-substituted anthracenes, fluorescence quantum yields increase steeply with decrease of temperature, while side-substituted derivatives have low yield and small temperature dependence. The variation is of the form... 

By the effect of ionization irradiation side substituents are abstracted from excited macromolecules in parallel to the scission of main chains. Elimination of side substitutions such as hydrogen and halogen atoms may be the main primary process. For instance, in polyethylene, although the C —H bond is stronger than the C—C bond, excited macromolecules eliminate hydrogen atoms preferentially through a C —C bond cleavage of a macromolecular backbone. Part of the... 

Distribution of amorphous scattering intensity, in particular, angular 20 position, depends on the sizes of cyclic fragment and side substituting agent (Figure 14). 

Muitipiy both sides by —1 and take the antiiog of each side. Substitute pH = 2.38. 

Elementary stages of tribochemical transformations. Tribochemical reactions in polymers usually follow a free-radical mechanism [78,80]. As a result of mechanical interactions pol3mier or low-molecular radicals appear, taking part in substitution, addition, decomposition or other reactions. On breakage of a macromolecule, two primary radicals with free valence at the chain ends are formed. In the vinyl series these radicals are CH2 and CXY (where X and Y are hydrogen atoms and other side substitutes) in... 

The highly ordered planar stmctures, as obtained by stereospecific polymerization, were mentioned in Section 2.3. In contrast to the branched chains, we deal here with linear chains where side substitute groups appear regularly on the same side of the plane, or alternatively. These structures are named isotactic or syndiotactic, respectively, and the degree of order is termed "tacticity." In both cases, good conditions for crystallization exist, even when the polymer itself is known as difficult to crystallize (as in the case of polystyrene or polymethylmethacrylate). Any orderless structure is named atactic. 

The periodate oxidation reaction can often be used to determine the location of a substituted hydroxyl in a molecule. Methyl jS-D-glucopyrano-side, substituted by 0-methyl on carbon 2 or 4, on 3, or on 6, consumes one, none, and two moles of oxidant, respectively, per mole of substance. The method has been extended to the determination of the types of linkages present in oligosaccharides (99) and to the determination of the degree of branching and of the types of linkages present in polysaccharides (103). (See Chapters IX and XII.)... 

Biotite (black mica) K(Mg,Fe)3(OH)j (AlSijOjQ) Type B + silicate on both sides. Substituted talc")) A black, brown, or dark green, foliated mineral, more common than muscovite )... 

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