Liebig and Wohler

Catalytic activities in plant extracts were also recognized early in the nineteenth century. Robiquet and Boutron (1830), for example, noted the hydrolysis of amygdalin, a glycoside in the seeds of bitter almonds Robiquet, and Liebig and Wohler then identified the enzyme responsible—emulsin. 

Gregory, J. prak. Chem., [1], 32,278 (1844), showed that dialuric acid gave a white precipitate with barium ion, but that it was readily oxidized by air to alloxantine, which gave a purple precipitate. The role of air in the formation of a purple barium salt from dialuric add was also appreciated by Liebig and Wohler, Ann. Chem., 26, 279 (1838). For a modem interpretation of the color of barimn alloxantinate, see Hantzsch, Ber. chem. Ges., 54, 1267 (1921) and Retinger, J. Am. Chem. Soc., 39, 1059 (1917). 

In 1776, Scheele first prepared cyanuric acid by pyrolysis of uric acid (7) (B-1793MI22000). In 1830, the first correct analysis was obtained by Liebig and Wohler (1835MI22000), but the molecular formula was incorrectly assigned as C6H6N606. Dreschel deduced the correct molecular formula, C3H3N3O3, in 1875 (1875JPR(11)289). Cyanuric acid does not have many industrial applications itself, but many of its derivatives are valuable monomers (see Section 2.20.5). 

We illustrate the sometimes conflicting results with several experiments involving the diketone benzil, originally prepared by Liebig and Wohler. Since neither the quadrivalence of carbon nor its proper atomic weight had been established, the compound was described as the radical benzoyl with a composition of C28H10O2. Laurent treated the new compound with potassium tartrate and observed a rose colored solution [34]. It is plausible that this reaction leads to the semidione in analogy to the formation of semiquinones under similar conditions. 

Liebig and Wohler, Pogg Annalen, 1831,21, 583 Lefort, Compt. rend., 1852,34, 488. 

Constitution.— The constitution of uric acid has been established by a remarkable set of syntheses based upon a study of the products of decomposition. In this work several men played an important part. The most comprehensive work which cleared up the question of the constitution not only of uric acid but of several related compounds, which we shall presently consider, was by Emil Fischer, whom we have already mentioned in connection with two other groups of compounds intimately connected with plants and animals, viz., the carbohydrates and the proteins (p. 393). Earlier important work was done by Liebig and Wohler, and the relationship of the decomposition products was mainly due to the work of Baeyer. The accepted formula was first suggested by Medicus, and the syntheses supporting it were worked out by Horbaczewski, and by Behrend and Roosen. 

The preparation of benzoyl cyanide on distillation of benzoyl chloride and HgCN, which was reported by Liebig and Wohler in 1832, has to be regarded as a cornerstone in nitrile chemistry, as this documents the first synthesis of an organic nitrile. Today numerous methods for the preparation of these important acylnitriles are known (equation 10). A number of review articles - provide quick access to the original papers, the very broad patent literature included. 

De Morveau (1787) and Lavoisier had nsed the term radical as that pewr-tion of an anhydrous acid that was combined with oxygen. Liebig and Wohler s benzoyl radical contains oxygen, Berzelius overlooked this in his first enthusiasm, but later suggested the oxygen be excluded from the radical of benzole acki.— O.T.B.]... 

Berzelius to Liebig and Wohler, 2 Sept. 1832. For manuscripts and unpublished letters, the following archives have been consulted Archives de I Academie des Sciences, Dossier Liebig, and Archiv der Justus Liebig Gesellschaft, Giessen. 

Nitriles had been known since the eighteen-thirties. CN played an important part in the development of the concept of the compound radical , and benzoyl cyanide was one of the compounds prepared by Liebig and Wohler in 1832 during their work which led to the recognition of the benzoyl radical. The first simple aliphatic nitrile to be made was... 

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