California Association of Chemistry Teachers
George B. Kauffrnan California State College a t Fresno Fresno, California
Foundation of nitrogen stereochemistry
Alfred Werner's Inaugural Dissertation
The year 1966 marks the hundredth anniversary of the birth of Alfred Werner, the first Swiss Nobel Priee winner in chemisty. Throughout the scientific world, centennial celebrations and meetings will he held in his honor. Prominent among these will he the Centemire de Werner a t Mulhouse in Alsace, Werner's birthplace, in May and the Alfred Werner Centenary Celebration a t Zii~ichand the ACS Alfred Werner Centennial Symposium a t New York, both in September. On these occasions, his achievements ss the great systematizer of inorganic chemistry, the inorganic Kekule, will he emphasized, and rightly so, for the influence of his coordination theory extended far beyond the confines of an unexplained class of compounds once known ss Molekduebrindungen to embrace ultimately almost the entire reelm of inorganic chemistry. The purpose of this paper, however, is to draw attention to a facet of Werner's work that is often slighted today-his many cont,ributions to organic chemistry,' particulilrly the stereochemistry of nitrogren compounds. Werner was trained primarily as a n organic chemist at the EidgenBssisehes Polyteehnikum in Ziirich, and, despite his later preoccupation with coordinilt,ioncompounds, his interest in organic chemistry continued throughout, the entire bhirty years of his scientific career. Of his 173 publications, 45 deal with organic themes such as oximes; hydroxamic and hydroximic acids; phenenthrenes; hydroxylrtmines; am, seoxy, hydazo, and nitro compounds; and dyestuffs. His investigations and interpretation of the Walden inversion [Bw., 44, 873 1911); Ann., 386, 1 (1911)l are still of value taday. Nevertheless, as the yews passed, his interests gravitated more and more to inorganic chemistry. Of his first 30 publications (1890-96), the organic papers outnumber the inorganic ones by a rat,io of two to one. I n a letter of November 25, 1897, Werner confided! t o his lifelong friend and former teacher Arthur Hiantssch: "Several times I wss a t the point of again turning completely to organic chemistry, a field in which I would certainly receive more recognition with less work; again and again I have felt compelled to return to inorganic chemistry, perhaps because I actually overestimate the importance of these mvestigations." I t was only in 1898, when his reputation in coordination ehemistry was already established, that the number of his inorganic papers ( 2 1 ) reached that of his organic ones. I n a letter of July 12, 1899, he announced his final decision to Hantzscb: "As I wrote to you previously, I had for some time intended to turn again to organic work; this periodic vacillation is now overcome. Inorganic chemistry presents me wit,h so many problems whose solutions attract me that I shall definitely take the path in the inorganic direction; dso, I hope to be able to achieve more there than in the organic field!' 'Werner's theoretical views on organic chemistry were the topic of s. small, obscure, and now rare book: BLOCH,ERNST, "Alfred Werner's Theorie des Kohlenstoflatoms und die Stermchemie der kmbacyklischen Verbindungen," Kaiserl. und kiinigl. Hof-Buchdruekerei und Hof-Verlae-Buchhandlung, Wien und Leipaig, 1903.
Yet, despite his commitment to coordination chemistry, Werner enriched the organic literature with 21 more papers. For example, s t the height of his career, after his long-sought resolution of coordinstion compounds had unequivocdly proven the correctness of his octahedral configuration for cobalt, chromium, and rhodium, he repaid his debt to Pasteor by using these optically active inorganic compounds, which had been resolved by means of organic substances, to resolve in turn dimethylsuccinic acid, an organic compound [Be?., 46,3229 ( 1 9 1 3 ) ) . Werner's earliest known original scientific work, a. holograph manuscript written in Mulhonse a t the age of 18 entitled "Contribution de I'acide urique, de series de la theahromine, eafhine, et de leurs derivhs" and, of course, only of historical interest, ends with a youthful enthusiasm that borders on braggadocio: "Thus this immense uric group has been developed with an extraordinary simplicit,y, and soon we shall have this area of organic chemistry arranged as orderly as few others." After a year's compulsory military service in the German army a t Xarlsruhe (1885-86) where he audited organic chemistry lectures a t the Technische Hochschule, Werner entered the world-famed Eidgeniissisches Polytechnikum at Ziirich (now the ETH), where he studied under Hantzsch, Lunge, Galdschmidt, and Constam. I n 1889, he became an unsalaried assistant (Hiljsassistent) in Lunge's lahomtory for preparative chemistry. His final paper written in 1889 far his doctoral degree (Clausura~beit) dealt with the topic "Uber die Theorie der aromatischen Verbindungen." Following his doctoral dissertation performed under Hantzsch's direction (1890), which is discnssed and translated below, Werner began work on his Habilitationsschrift, hut also found time to broaden his experience by spending the winter semester of 1891 working on thermochemical research with Marcellin Berthelot a t the Collhge de France in Paris. I n his Habilitatimssehrifl, "Beitrage zur Theorie der Affinitat und Vdens;' a e r Stereochemie des Stickstoffs in der Benzhydraxamsiiurereihe," Werner attempted to replace KekulB's concept of rigid directed valencies with a more flexible approach in which he viewed valency ss a force emanating outward from sn atom equally in all directions. Although this paper contains the seeds which were to flower forth two years later in his famous coordination t,heorv.a it deals exclusivelv with oreanic comoounds. I t s acceptance by the faculty permittei Werneryat 25, tobecome on January 4, 1892, an unsalltried instrnetor (PrivadDorent)
The firat and theoretical part of this work was published sepsrstely in a rather obscure journal (Vierleljahrssehrifl der Ziircher fiaturjorsehenden Gesellschaft, 36, 129-169 ( 1 8 9 1 ) ) , where it elicited lit,t,le nobice until brought to the sttenlion of the scientific world by its discussion in WERNER'S"Lebrbuch der Stereoehemie," Verlag van Gustav Fisrher, Jena, 1904, a. predominantly organic text. a An English translation of this paper, "Beitrag zur Konstit,ution anorganischer Verbindungen," and of five other papers G. B., ' ' C ~ S S ~in C SCOby Werner will appear in KAUFFMAN, ordination Chemistry, Part I, The Selected Papers of Alfred Werner," Dover Publications, Inc., New York, 1966. Volume 43, Number 3, March 1966
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a t the Polytechnikr~mwhere he taught atomic theory, campamtive organic chemistry, selected topics in inorganio chemistry, and stereochemistry (largely organic). I n his public inaugural addrew (Anlritlsvorlesung) entitled "Xrilisehe Beleucht,ung der heutigen Benzoltheorie" (available as a holograph manilscript only), bhe young Dozat pointed out the short,comings of the varioiis structures mouosed for benzene bv Keknle. Clitus. Loschmidt, Thornsen, ~ a i h s eand , others and proposed his ownaolution to a perennially popular organic problem. Werner's tenure at the Polytechnikum was not a. long one, however, for the fallowing year (1893), largely as a result of his paper on the roordination theory, he rereived a call as Ezlmordilzarius (Ausseronl~nllicher) Professo~ from Universitfit Ziirich, where he remained for a qnsrter of a century until his untimely death in 1919 al the axe of 52. At this institution too. ~ e r n e r ' steaehine duties o r i m a h involved oreanic chemistrv. and it was not h i l the 'winter semester 1 9 0 5 3 that he whs finally assigned tile colirse in inorganic chemistry, he con. tinued to teach along with organic chemistry thronghont his career. But it is Werner's first publication, excerpted from his doctoral dissertation, that remains his most popular and important work in the organic field. "Ueber rtiumlirhe Anordnuug der Atome in stiekstoffhaltigen ~ l o l e k i i l e n " ~appeared in Berichle d w Deutschen Ch,misehen Ge.sellsehqfl, Yolume 23, pages 11-30 (1890) under the names of Hantzsch and Werner, and for the firs! time the stereochemistry of nitrogen compounds was placed on a firm theoretical hasis. I n this paper, Hantzseh was careful to acknowledge Werner's major role in the development of the eoncept of the tetrahedral nitrogen atom. However, despite a n u m ber of publications on oximes and other organic nitrogen derivatives by Werner, it was primarily Hantzsch'n numerous subsew e n t researches, particularlv on aromatic a m and diazo compounds, lhnt won aeceptsnce-for the new theory. In his opinion concerning Werner's petition for the v a i a leoenrli (t,he urivileee of sivine lectures s t a universitv). Ham-
"he other parts of the dissertat,ion are entitled "Ueber ein zweite. Benminoxim" (Be?., 23, 2333 (1890)), "Versuch aur Darstellung stereochemisrh isomerer Kiirper der Furfuraldoximreihe" (Ijcr., 23,2336 (1890)), and "Ueher die sngeblirh isomeren Paraamidoi~zobenaolsulfor~sduren" (not puhlished).
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Alfred Werner (left) and Arthur Hontzrch. Leipzig, summer of I910 (tour'e'yaFrouSuranne LGh'ein'nee Hontzrch)'
only has rontribnted materially to the explamtiun of the wellknown cases of geometric isomerism but has also led to numerous discoveries of new stereoisomeric compounds." In spit,e of early attacks on the theory by Victor Meyer and Karl von Auwem, and later attacks by Engen Bmherger and other chemists extending into the third decade of the present century, Werner and Hautzsch's view has withstood the test of time. Today, with only slight modification, it takes its rightful place alongside the 1.e Bel and van't Haff concept of the tetrahedral carbon atom as one of t,he foundations of stereochemistry. I t is hoped that the following translation will make this classic better known to English speaking chemists, scientific historians, . "uaent'. . . .
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The author wishes to acknowledge the finmcial support of the History and Philosophy of Science Program of the NSF Division of Social Sciences, nnd of t,he American Philosophical Society, which made possihle a year's atndy of Alfred Werner's coordination theory at Universitit Ziirich. He also wishes ti, t,hank F r i d e i n Charlattc Werner far graciously making available her father's papers, manuscripts, letters, and pictures. Thanks are d s o due l o Frau S~manneLiihlein (n6e Hant,zsch) for the phdograph of Werner and Hantasch and to Dr. Richard P. Cinla for vnluahle diso~msionsof organic stereochemistry.
