Poisons, Their Effects and Detection / A Manual for the Use of Analytical Chemists and Experts

by Alexander Wynter Blyth

Observation has shown that both of these requirements are satisfied; phenylenediamine is more poisonous than aniline; toluylenediamine more poisonous than toluidine. Again, if an atom of hydrogen in the amido (NH₂) group in aniline be replaced by an alkyl, e.g. methyl or ethyl, the resulting substance does not produce muscular spasm; but if the same alkyl is substituted for an atom of hydrogen in the benzene nucleus the convulsive action remains unaffected.

If an acidyl, as for example the radical of acetic acid, enter into the amido group, then the toxic action is notably weakened; thus, acetanilide is weaker than aniline, and acetylphenylhydrazine is weaker than phenylhydrazine. If the hydrogen of the imido group be replaced by an alkyl or an acid radical, and therefore tertiary bound nitrogen restored, the poisonous action is also weakened.

In xanthin there are three imido groups; the hydrogen of two of these groups is replaced by methyl in theobromin; and in caffein the three hydrogens of the three imido groups are replaced by three methyls, thus:—

Xanthin.

Theobromin.

Xanthin.