Piperic acid differs from piperonylic acid by the group C4H 4, and it was apparent that these carbon atoms must be attached to the carbon atom which appears in the carboxyl group of piperonylic acid, for if they were directly attached to the benzene ring polycarboxylic acids would result in oxidation.
Benzene is very stable to oxidants, in fact resistance to oxidation is a strong characteristic of the benzene ring.
He determined that definite absorption bands are only produced by substances in which three pairs of carbon atoms are doubly linked together, as in the benzene ring.
An aromatic primary amine is one in which the -NH 2 group is attached directly to a benzene ring.
This produces an electron which adds to the benzene ring to generate a radical anion.
