Classification of substituent groups

Studies of electrophilic substitutions on arenes are reported in which the experimental conditions allow a direct comparison of the relative reaction rates. For example, the relative reactivities of benzene and toluene toward halogenation, acetylation, sulfonation, nitration, and methylation have been determined. In all cases, electrophilic aromatic substitution was more rapid with toluene. For example, bromina-tion of toluene is some 600 times faster than that of benzene. Such studies have led to the classification of substituents as ring activators or deactivators, depending on whether the substituted arene reacts faster or slower than benzene itself. Thus, the methyl group of toluene is a ring activator. 

The other structural parameters, such as the ester group content, the presence, nature, and position of substituents on monomer units, and the number and nature of comonomers, are of less importance and do not modify this classification of hnear polyesters. 

Make a classification of the type of substituent we can put on a carbonyl group so that it... 

In this section, the classification of carbenes and carbenoids bearing two different substituents is made by giving priority to the functional group which will appear in the later... 

Chemical classification of polysaccharides is the least ambiguous system of grouping these macromolecules. Polysaccharides of different origins can have similar structures, as Kravtchenko et al. (1992) discovered in lemon and apple pectin. Likewise, polysaccharides of the same origin can have different structures, as for example, the concentration of pyruvate and acetyl substituents in xanthan, depending on incubation conditions (Pettitt, 1982). 

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