Aromatic compounds and their derivatives

All drugs are chemicals and many of them are aromatic compounds. Therefore, in order to understand the chemical nature, physical properties, stability, pharmacological actions and toxicities of a majority of drug molecules, the knowledge of aromatic chemistry is extremely important. Before we look into the specific examples of various drugs that belong to this aromatic class, let us try to understand what aromaticity really is. 

Generally, the term aromatic compounds means fragrant substances. Later, benzene and its structural relatives were termed as aromatic. However, there are a number of other nonbenezenoid compounds that can be classified as aromatic compounds. 

An aromatic compound has a molecular structure containing cyclic clouds of delocalized tt electrons above and below the plane of the molecule, and the TT clouds contain a total of 4n -f 2) tt electrons (where n is a whole number). This is known as Hiickel s rule (introduced first by Erich Hiickel in 1931). Eor example, benzene is an aromatic compound. 

If n = 1, we have 4 x 1+2 = 6, which means that any compound containing a total number of six tt electrons is an aromatic compound. In the above structure of benzene, there are three double bonds and six tt electrons, and it is a planar molecule. Thus, benzene follows Hiickel s rule, and is an aromatic compound. 

Aromatic compounds have the following general properties. 

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The composition of coal tar varies with the carbonization method but consists, largely, of mononuclear and polynuclear aromatic compounds and their derivatives. Coke oven tars are relatively low in aliphatic and phenolic content while low-temperature tars have much higher contents of both. 

Ground and Excited-state pK Values for other Polycarbocyclic Aromatic Compounds and their Derivatives... 

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