Selling a Theory: The Role of Molecular Models in J. H. van 't Hoff's Stereochemistry Theory

Summary

In 1874, the Dutch chemist and Nobel prizewinner Jacobus Henricus van 't Hoff (1852–1911) laid the foundations for stereochemistry with a publication in which he openly suggested that molecules were real physical entities with a three-dimensional structure. He visualized this new spatial concept with illustrations, but also with the help of small cardboard molecular models, which he made himself. Some of these models have survived the ravages of time and are among the oldest molecular models in the world still in existence. What is more, they are the first material models of a three-dimensional molecular structure ever made. This article describes the surviving Van 't Hoff models, kept in Museum Boerhaave in Leiden and in the Deutsches Museum in Munich. Special attention is paid to the use of these models and the specific purposes they served. A closer examination of the models and their context reveals that they had an essential part to play in the early development and spread of Van 't Hoff's stereochemistry theory: he put his molecular models not only to versatile use as didactic tools, scientific instruments, and precursors to experimental proof, but also as devices to persuade other scientists of the usefulness of his theory.

Acknowledgments

The author wishes to thank Dr Elisabeth Vaupel of the Deutsches Museum in Munich, Dr Peter Ramberg of Truman State University, Missouri, USA and Prof Dr Ernst Homburg of the University of Maastricht, The Netherlands, for their help and critical remarks.

Notes

¹U. Klein, ‘The Creative Power of Paper Tools in Early Nineteenth-Century Chemistry’, in Tools and Modes of Representation in the Laboratory Sciences, edited by U. Klein (Dordrecht, 2001), 13–35 (28). P. J. Ramberg, ‘Paper Tools and Fictional Worlds: Prediction, Synthesis and Auxiliary Hypotheses in Chemistry’, same publication, 61–79 (62). E. Francoeur, ‘Molecular Models and the Articulation of Structural Constraints in Chemistry’, same publication, 95–117 (96–98). See also U. Klein, Experiments, models, paper tools: cultures of organic chemistry in the nineteenth century (Stanford, CA, 2003) on the use of paper tools in organic chemistry. Eric Francoeur wrote several articles on the use of molecular models in the late nineteenth and twentieth centuries, but he did not include the earliest models. The history of these molecular models is described in C. Meinel, ‘Molecules and Croquet Balls’, in Displaying the Third Dimension: Models in Science, Technology, and Medicine, edited by S. H. de Chadarevian and N. Hopwood (Stanford, CA, 2004), 242–76.

²Jacobus Henricus van 't Hoff (1852–1911) studied mathematics and physics at the University of Leiden and received his doctoral degree in chemistry at the University of Utrecht on 22 December 1874. He subsequently worked as a teacher at the Veeartsenijschool in Utrecht (1877) and as a lector and subsequently professor in Amsterdam (1878–1892) and in Berlin (1892–1911). In 1893, he shared the Royal Society's Davy medal with J. le Bel for his contribution to stereochemistry. In 1901, he was awarded the Nobel Prize for Chemistry for his work on physical chemistry. More biographical information can be found in: E. Cohen, Jacobus Henricus van 't Hoff: sein Leben und Wirken (Leipzig, 1912).

³Deutsches Museum inventory number 4680; Museum Boerhaave inventory numbers 31272 and 10239. Museum Boerhaave has a large amount of ‘Van 't Hoffiana’ in its collection, including his molecular models, various personal belongings and the major part of his archive (archive 208). Another part of his archive is kept at the John Hopkins University in Baltimore, USA.

⁴J. A. le Bel, ‘Sur les relations qui existent entre les formules atomiques des corps organiques, et le pouvoir rotatoire de leurs dissolutions’, Bulletin de la Société Chimique de France, (2), 22 (1874) 337–47. J. H. van 't Hoff, Voorstel tot uitbreiding der tegenwoordig in de scheikunde gebruikte structuur-formules in de ruimte: benevens een daarmee samenhangende opmerking omtrent het verband tusschen optisch actief vermogen en chemische constitutie van organische verbindingen (Utrecht, 1874). A full, revised English translation of this pamphlet was published in 2001: P. J. Ramberg, and G. J. Somsen, ‘The Young J. H. van 't Hoff: The Background to the Publication of his 1874 Pamphlet on the Tetrahedral Carbon Atom’, Annals of Science, 58 (2001) 51–74.

⁵An extensive reading of this period and especially the settings in which Van 't Hoff wrote his theory and made his models can be found in: Stereochemistry, edited by O. B. Ramsay (London, 1981) and P. J. Ramberg, Chemical Structure, Spatial Arrangement, The Early History of Stereochemistry, 1874–1914 (Aldershot, UK, 2003).

⁶C. Ritter, ‘An early history of Alexander Crum Brown's graphical formulas’, in: Tools and Modes of Representation in the Laboratory Sciences, edited by U. Klein (Dordrecht, 2001), 35–46.

⁷This was the Friday Evening Discourse, 7 April 1865, Royal Institution, London. C. Meinel, ‘Molecules and Croquet Balls’, in Displaying the Third Dimension: Models in Science, Technology, and Medicine, edited by S. H. de Chadarevian and N. Hopwood (Stanford, CA, 2004), 242–76.

⁸F. R. Japp, ‘Kekulé Memorial Lecture’, in Memorial lectures delivered before the Chemical Society 1893–1900 (London, 1901), 97–138. Citation: The four units of affinity of the carbon atom, instead of being placed in one plane, radiate from the sphere representing the atom in the direction of hexahedral axes, so that they end in the faces of a tetrahedron (. . .) A model of this description permits of the union of 1, 2 and 3 units of affinity, and, it seems to me, does all that a model can do.

⁹J. H. van 't Hoff, Die Lagerung der Atome im Raume, 2nd edition (Brunswick, 1894), 2.

¹⁰C. Meinel (note 7). P. Ramberg (note 5), 56.

¹¹J. H. van 'Hoff (note 9), 1–2.

¹²P. J Ramberg (note 5), 50–52.

¹³P. J. Ramberg, G. Somsen (note 4), 63.

¹⁴J. H. van 't Hoff, ‘Sur les formules de structure dans l'espace’, Archives Néerlandaises des Sciences Exactes et Naturelles, 9 (1874), 445–54. H. A. M. Snelders, ‘The reception of J. H. van 't Hoff's Theory of the Asymmetric Carbon Atom’, Journal of Chemical Education, 51 (1974), 2–7. Only Professor Buys Ballot in Utrecht wrote a public reaction. The text of his open letter to Van 't Hoff is published in E. Cohen, Jacobus Henricus van 't Hoff: sein Leben und Wirken (Leipzig, 1912), 94–104.

¹⁵J. H. van 't Hoff, La chimie dans l'espace (Rotterdam, 1875).

¹⁶J. H. van 't Hoff (note 15).

¹⁷J. H. van 't Hoff (note 15). As far as we know, none of these sets has survived.

¹⁸J. H. van 't Hoff (note 15), 7, footnote 1.

¹⁹See note 3.

²⁰The Leiden 2 set of 69 models has only ever been mentioned in a footnote to a Dutch article in 1924: W. P. Jorissen, ‘Eenige Brieven van Van 't Hoff (1874–1875)’, Chemisch Weekblad, (21), 43 (1924), 495–501 (497). The German set in the Deutsches Museum in Munich was described by O. B. Ramsay, ‘Molecular Models in the Early Development of Stereochemistry’, in Van 't Hoff-Le Bel Centennial, edited by O. B. Ramsay (Washington, DC, 1975), 74–96. Ramsay's article contains several observations that need adjustment, for instance the numbering of the models. Therefore, some discrepancies may exist between Ramsay's description and that given in this article. The Leiden 1 set was described by H. A. M. Snelders, ‘The reception of J. H. van 't Hoff's Theory of the Asymmetric Carbon Atom’, Journal of Chemical Education, 51 (1974), 2–7.

²¹An administration copy of the letter of thanks, dating from 2 April 1906, is kept in the archive of letters of the Deutsches Museum (‘Chemie’, VA-1252, subletter H). In this letter, the museum director described the models as ‘Originalen ihrer Modellen’. The acquisition is described in the annual report of the Deutsches Museum, 1906. See also a calligraphed letter dated 7 January 1909, in archive 208, Museum Boerhaave, Leiden.

²²The manual is described in the letter of thanks that Oscar von Millar sent to Van 't Hoff on 2 April 1906 (see note 21) but could not be traced in the archives of the Deutsches Museum.

²³J. H. van 't Hoff (note 15).

²⁴See note 21.

²⁵Gustav Bremer's widow donated the set to the Chemistry Department of the University of Leiden after his death in 1909, where it was kept until recently.

²⁶J. H. van 't Hoff (note 15), 16, including footnotes. See models no. XIII–XVII, present in the German set and the Leiden 2 set.

²⁷J. H. van 't Hoff, Die Lagerung der Atome im Raume (Brunswick, Vieweg, 1877), 46–53.

²⁸In a letter to W. P. Jorissen on 12 May 1911, Bremer's widow described the close contact between her late husband and Van 't Hoff in the 1870s and the fact that the molecular models in her husband's legacy were produced by Van 't Hoff only (Museum Boerhaave, archive of ‘Bremer’ letters, arch 1).

²⁹Ten cardboard models, inventory number 10239. Eight letters from Van 't Hoff to Bremer, written in late 1874 and 1875 (archive of ‘Van 't Hoff’ letters, arch 1). The eight letters were published by W. P. Jorissen, ‘Eenige brieven van Van 't Hoff (1874–1875)’, Chemisch Weekblad, (21), 43 (1924), 495–501. Chronological rearrangement of these letters by E. Fischmann, ‘A reconstruction of the First Experiments in Stereochemistry’, Janus, 72 (1985), 131–56. Letter number 3, dating from 13 July 1875, contains a ‘manual’ for the use and meaning of the cardboard objects. Surprisingly, Jorissen reported the ten molecular models comprising the Leiden 1 set missing in 1924. Obviously, they were rediscovered, because they came to the museum after Bremer's widow died in 1936.

³⁰For instance, O. B. Ramsay (note 20), 85.

³¹Letter no. 7 according to E. Fischmann (note 29). Gustav Bremer published part of his experimental results in his dissertation Een rechtsdraaiend appelzuur (Assen, 1875). He received his doctoral degree in Utrecht on 15 October 1875.

³²Date based on Van 't Hoff's remark that he was surrounded by the papers of his dissertation when he wrote this letter. He received his doctoral degree on 22 December 1874. Unfortunately, the ink of this letter is strongly bleached.

³³Van 't Hoff had already suggested in his Dutch publication (see note 4) that a compound with more than one asymmetric carbon atom must have many stereoisomers, but he did not explain this statement any further with examples or calculations. In the letter to Bremer dating from December 1874, he became more specific on this point.

³⁴W.P Jorissen and E. Fischmann (note 29).

³⁵Despite the fact that Van 't Hoff urged him to do so, Bremer seems not to have used the ‘interactive’ feature of the drawing: the letter shows no signs of having been folded.

³⁶J. H. van 't Hoff (note 27), 46–53. This publication dates from February 1877.

³⁷The colour code on the surviving models consists of ‘white’ (transparent), yellow, red and blue. See: J. H. van 't Hoff (note 15), 7 and 11. In 1877, the code changed to white, black, red, and blue, and had to be applied with sheets of coloured paper. A detailed description of this technique can be found in: J. H. van 't Hoff, Die Lagerung der Atome im Raume (Brunswick, 1877), 46–53.

³⁸See note 8.

³⁹P. J. Ramberg (note 5), 81–84; O. B. Ramsay (note 5), 85–87.

⁴⁰J. H. van 't Hoff's Dutch publication dating from September 1874 (note 4) contains the first illustrations of apex-centred tetrahedrons, while the first face-centred example is found in a drawing dating from December of the same year; see section 2.4.

⁴¹Van 't Hoff referred to the similarity of the face-centred and the apex-centred models several times, e.g. in J. H. van 't Hoff (note 15), 7, footnote 2; J. H. van 't Hoff, Maandblad der Natuurwetenschappen, 6, 3 (1875), 37–45 (41). Letter no. 3 to Bremer according to E. Fischmann (note 29), original citation: (. . .) de aanhangende groepen zijn voorgesteld door de vlakken, omdat dit, 't zelfde resultaat opleverende als de hoekpunten, 't voordeel heeft van door kleuren overeenkomst of verschil van groepen aan te wijzen: H—wit, OH—geel, CO ₂ H—rood, CH(OH)CO ₂ H of CH ₂ .CO ₂ H—blauw. (. . .). English translation: (. . .) the attached groups are represented by the faces because this—since it generates the same result as when the apexes are used—has the advantage that similarities or differences between the groups can be pointed out by using colours: H—white, OH—yellow, CO ₂ H—red, CH(OH)CO ₂ H of CH ₂ .CO ₂ H—blue (. . .).

⁴²J. H. van 't Hoff (note 27), 46–47.

⁴³J. H. van 't Hoff (note 15), 7, footnote 1.

⁴⁴Letter no. 3 according to E. Fischmann (note 29).

⁴⁵J. H. van 't Hoff (note 4).

⁴⁶The precursor of Van 't Hoff's models is described in section 2.4.

⁴⁷O. B. Ramsay (note 20), 82.

⁴⁸Model XX (figure XXIX in the text).

⁴⁹O. B. Ramsay (note 20), 82.

⁵⁰J. H. van 't Hoff (note 15), 7, footnote 1; J. H. van 't Hoff (note 27), 5, footnote. Original phrase: für den Zweck der Anschauligkeit is unerlässlich die Contruction von Modellen aus Cartonpapier.

⁵¹Anonymous, ‘Vorstellung über die räumliche Lagerung der Atome’, Der Naturforscher, 9, 19 (1876). Article kept in Museum Boerhaave (arch 208). Original citation: der Brochüre des Herrn van 't Hoff ist eine grosse Anzahl aus Pappe gefertigter Modelle beigegeben, welche das Verständniss wesentlich erleichtern.

⁵²P. J. Ramberg (note 5), 87–101.

⁵³P. J. Ramberg, ‘Paper Tools and Fictional Worlds: Prediction, Synthesis and Auxiliary Hypotheses in Chemistry’, in: Tools and Modes of Representation in the Laboratory Sciences, edited by U. Klein (Dordrecht, 2001), 61–79 (62–69).

⁵⁴Van 't Hoff had already postulated this hypothesis in early 1875 (letter no. 2, according to E. Fischmann) (note 29) but worked it out in more detail with the help of models in the letter of 13 July (letter no. 3, according to E. Fischmann).

⁵⁵The two single tetrahedron models of tartaric acid can be combined to make a double tetrahedron model of the same compound because the structural formula of tartaric acid is symmetrical. The two single tetrahedrons are placed against each other with the face that represents the largest chemical group, which is identical on both models. The single tetrahedrons thus exactly replace the written formula on the shared face by its spatial representation and combine to make a model that illustrates the spatial surrounding of two adjacent asymmetric carbon atoms. The possible co mbinations are: models VIII and IX combining to make model I, models VIII and II combining to make model VI, and models II and III combining to make model VII.

⁵⁶The magnitude A is of opposite sign for stereoisomers. Models II and III are mirror images of the models VIII and IX, so their optical activity is symbolized by –A, resulting in –A – A = –2A for model VII.

⁵⁷The conversion of tartaric acid into malic acid can take place at either of the two asymmetric carbon atoms because of the symmetrical structural formula of tartaric acid.

⁵⁸E. Fisher, ‘Gedächtnisrede auf Jacobus Henricus van 't Hoff’, Gedächtnisrede Jahrgang 1911, 1 (Berlin, 1911), 5. Original citation: Was van 't Hoff an der Hand seines Modells auch für solche komplizierten Fälle inbezug auf Konfiguration, optisches Drehungsvermögen, Anzahl der Formen usw. vorausgeschaut, ist dann in geradezu staunenderregender Weise bestätigt worden.

⁵⁹J. H. van 't Hoff (note 15), 7, footnote 1.

⁶⁰C. Meinel (note 1).

⁶¹See note 7.

⁶²Arthur Henninger, a friend of Van 't Hoff who worked in the laboratory of Adolphe Wurtz in Paris, presented Van 't Hoff's theory to a French audience on 19 March 1875.

⁶³The letter is published in E. Cohen (note 2), 114–15.

⁶⁴J. Wislicenus addressed the Zürich chemical club on 2 November 1869. Citation: Die Thatsachen zwingen dazu die Verschiedenheit isomerer Molecule von gleicher Structurformel durch verschiedene Lagerung ihrer Atome im Raum zu erklären. Reported in: O. Meister, Berichte der Deutschen Chemischen Gesellschaft, 2 (1869), 620.

⁶⁵Original citation in E. Fisher (note 59), 5, English translation by P. J. Ramberg (note 5), 88.

⁶⁶See note 55. P. J. Ramberg (note 5), 87–101.

⁶⁷J. H. van 't Hoff (note 27), 5, footnote. Original phrase see note 54.