Benzo-ortho-diazines exist in two structural forms, cinnolin and phthalazine; benzo-meta-diazines are known as quinazolines; benzo-para-diazines are termed quinoxalines; the dibenzo-compounds are named phenazines, this last group including many valuable dyestuffs - indulines, safranines, &c. In addition to the types of compounds enumerated above we may also notice purin, tropine and the terpenes.
Hydrolysis with hydrochloric acid or baryta water gives tropic acid and tropine; on the other hand, by boiling equimolecular quantities of these substances with dilute hydrochloric acid, atropine is reformed.
It sometimes separates with crystals of a solute as " benzene of crystallization," as for example with triphenylmethane, thio-p-tolyl urea, tropine, &c.
Pseudopelletierine (methyl granatonine), C9H15N0, an alkaloid of the pomegranate, is a derivative of cyclo-octane, and resembles tropine in that it contains a nitrogen bridge between two carbon atoms. It is an inactive base, and also has ketonic properties.
Since both these substances have been synthesized (see Tropine), the artificial formation of atropine is accomplished.
The drug is often replaced in ophthalmology by homatropine - an alkaloid prepared from tropine - which acts similarly to atropine but has the advantage of allowing the ocular changes to pass away in a much shorter time.
The presence of the heptamethylene ring in these compounds is shown by the production of suberone by the exhaustive methylation, &c., of hydroecgoni dine ethyl ester (see POLYMETHYLENES and TROPINE).