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The conviction accordingly forces itself upon us that, if we want to attack the problem of building up any of these important alkaloids artificially, we must turn to these bases as our starting point. As already stated, both series occur in coal-tar and the pyridine series also more abundantly in bone-oil.
The study of the decomposition products of the cinchona alkaloids especially points quite distinctly to the probable existence in quinine of a hydrogen addition product of pyridine, in combination with a methyl-quinoline group. The many experiments that are now being made to test this and other questions that suggest themselves, will not long leave us in the dark.
Piperine has also been made by the uniting of piperidine and piperic acid, and, as piperidine has already been formed from pyridine, we have here a true synthesis also. Both theobromine and caffeine, its methyl derivative, have been made from xanthine, which itself can be formed from guanine, a constituent of guano.
Heated with bromine water to 120°C. it decomposes into bromoform, carbon dioxide, nitrogen, and pyridine. Turning now to the non-volatile and oxygenized bases, we take up first the opium alkaloids. Morphine, C H NO , is a tertiary amine, and appears to contain a hydroxyl group like phenols, to which class of bodies it has some analogies, as is shown in its reaction with ferric chloride.
Nicotine, C H N , the next simplest in formula of the alkaloids, is a tertiary base, that is, contains no replaceable hydrogen atoms in its molecule. It shows very close relations to pyridine. When nicotine vapor is passed through a red-hot tube, it yields essentially collidine, and, with this, some pyridine, picoline, lutidine, and gases such as hydrogen, marsh-gas, and ethylene.
Indeed, Ladenberg has recently succeeded in obtaining benzol as an alteration product from pyridine, in certain reactions. We may now look at the question of the decomposing effect of reagents upon the alkaloids.
When cinchonine is distilled with solid potassium hydrate, it yields pyrrol and bases of both the pyridine and quinoline series. Cinchonidine, when heated with potassium hydrate, yields quinoline also, and with nitric acid the same products as cinchonine. Strychnine has been found to be a tertiary amine. When distilled with potassium hydrate, quinoline is formed.
By the action of sodium upon pyridine is produced a compound C H N , known as dipyridyl, and this, under the influence of nascent hydrogen, takes up six atoms and becomes isonicotine C H N , a physiologically active alkaloid, isomeric with the true nicotine.
If, having completed our survey of what has been done in the way of decomposing the alkaloids by the different classes of reagents, we review the field, it will be seen that with all the alkaloids mentioned, except the last four, a more or less immediate connection with the pyridine and quinoline bases has been indicated.
When boiled with alcoholic potash solution, it takes up a molecule of water and splits apart into piperic acid, C H O , and piperidine, C H N. This latter base has been shown to be a hydrogen addition product of pyridine, C H N. When heated with concentrated sulphuric acid, it is oxidized to pyridine.
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