ABSTRACT
Phenylalanine and tyrosine are clearly both benzene based, with their aromaticity arising from the six pi electrons in the six carbon-centered ring. In addition to the aromatic character of tyrosine, its side chain can also act as a weak acid. When the ‘OH’ group is deprotonated, the resultant negative charge (pair of electrons) on the oxygen atom becomes part of the delocalized pi system and a number of resonance or canonical forms (Section I3) for this ion may be drawn (Figure 2).
