Thus the groupings J_C C - - C C - >N CH 3 and - C C C N exist in the molecule, and the alkaloid is to be represented as a-pyridyl-N-methyl-pyrollidine.
In the course of the 19th century the idea that the different elements are constituted by different groupings or condensations of one primal matter - a speculation which, if proved to be well grounded, would imply the possibility of changing one element into another - found favour with more than one responsible chemist; but experimental research failed to yield any evidence that was generally regarded as offering any support to this hypothesis.
We now proceed to discuss the types of aliphatic compounds; then, the characteristic groupings having been established, an epitome of their derivatives will be given.
Examination of the absorption spectra of coloured compounds shows that certain groupings displace the absorption bands in one direction, and other groupings in the other.
It follows on this theory that all coloured substances contain either of the groupings or the former being a para-quinonoid, the latter an ortho-quinonoid.