Chemical Constitution
The empirical formula of the uric acid molecule, C₅H₄N₄O₃, has for long been known, but it was reserved for Emil Fischer to reveal the chemical structure thereof. Through his labours we now know that uric acid is one of a group of substances which owe their kinship to their possession in common of the heterocyclic ring termed by Fischer the “purin nucleus” (1898).
The intimate relations of the purins of bio-chemical interest to the purin nucleus, and alike to each other, will be rendered more intelligible by examination of their structural formulæ as hereafter given. All, as will be seen, are derivatives of a synthetically formed body purin which, though unimportant in itself, is yet interesting in that it is the basic substance from which the following take origin:—
| Purin | C₅H₄N₄ | |||
| Hypoxanthine | C₅H₄N₄O | Monoxy-purin | } | |
| Adenine | C₅H₃N₄NH₂ | Amino-purin | } | |
| Xanthine | C₅H₄N₄O₂ | Dioxy-purin | } | Purin Bases. |
| Guanine | C₅H₃N₄ONH₂ | Aminooxy-purin | } | |
| Uric acid | C₅H₄N₄O₃ | Trioxy-purin | } |
It now devolves upon us to note the arrangement of the atoms in the purin nucleus. To each atom is affixed a number indicating the exact location of the various atoms and groups attached to the said nucleus. The manner in which the various purin bodies are built up around the purin nucleus C₅N₄ will become apparent from a study of the following structural formulæ culled from Wells’ “Chemical Pathology”:—