EXHIBIT C Carbocations

Carbocations ould not be confused with free radicak or carbanions. A free radical is similar to a carbocation in that it has three bonds, but rather than having a deficit of two electrons, a free radical has one unshared electron and, as a result, is highly reactive. A carbanion has an unshared pair of electrons in addition to three bonds and carries a negative charge. A carbene carbon has two bonds and one unbared pair of electrons. Caibenes are rarely isolated, becauseof their prt Tensiiy to react with one another to form dimers. 

The following dye is used as indicators in acid-base titrations Rationalize the color changes. 

Answer The amine groups are protonated under acidic conditions and deproto-nated in neutral-to-mildly-basic color ranges. Deprotonation has the same effect here as it did with phenolphthalein, allowing unshared pairs of electrons to interact with the aromatic system. Under acidic conditions and protonation, there is less conjugation than under basic and unprotonated conditions.The indicator is cyanine. 

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