Pi electron distribution

Figure 13.1 illustrates a number of principles in spectrophotometric analysis. The absorbance value of each species is, according to Beer s Law, proportional to its concentration in the solution, and can be seen to change dramatically with the wavelength. The figure also shows how a spectrum can change when the species is protonated. The pi electron distribution of the indicator molecule is sensitive to the incorporation of the proton, which is why it fimctions as an acid-base indicator. 

Arenes, including reaction mechanisms and nature of the bonding in terms of pi-electron distribution. Video clips on this site about nomenclature of aromatic compounds and electrophilic substitution in benzene. 

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