(b. Mannheim, Germany, 2 July 1842; d. Breslau, Germany [now Wroclaw, Poland], 15 August 1911)
Ladenburg poineered investigations of organic compound of silicon and tin and advanced theories on the structure of aromatic compounds, but his chief contributions were the elucidation of the structure of alkaloids and their synthesis.
Ladenburg was one of eight children. His father, a prosperous attorney, objected tot he classical education given at Gymnasium and sent him to a school where little Latin and no Greek were taught. A the Polytechnicium in Karlsruhe he emphasized study of mathematics adn languages, attempting to fill in the gaps of his earlier education. In 1860 Ladenburg went to Heidelberg and, inspired by Bunsen’s and Kirchhoff’s lectures, decided on chemistry, taking the Ph.D., summa cum laude, in the spring of 1863. He stayed on for two years, working with Ludwig Carius, beginning a lifelong friendship with Erlenmeyer, and shifting his interest from inorganic to organic chemistry. Ladenburg worked under Kekulé at Ghent in 1865; but despite the scientific excitement he found life at Ghent dull, and after a visit with Frankland in London, he began working with Wurtz in Paris.
Late in 1866 Friedel invited Ladenburg to work with him at the École des Mines, where they began research on the compounds of silicon. Their concern centered on whether the new theories being developed about carbon compounds were applicable to the socalled inorganic elements and their compounds. Preliminary to synthesizing compounds containing two silicon atoms bonded to each other, they prepared dimethyldiethylmethane, the first known quarternary hydrocarbon, demonstrating that carbon can bond to four other carbon atoms as silicon was shown to do by Friedel and Crafts in their compound Si (C2 H5)4. They also prepared silicon analogues of carboxylic acids, ethers, ketones, and alcohols. Believing that compounds of the lower oxidation states of metals contained two atoms of the metal per molecule, Ladenburg began the study of tin compounds. He prepared various organotin compounds, including triethylphenyl tin, but soon realized that such compound could not resolve the question.
Landenburg qualified as a teacher in January 1868, set up a laboratory in Heidelberg, and taught a course on the history of chemistry, publishing the revised lectures in 1869. That same year he criticized Kekulé’s formula for benzene and suggested alternatives, including his prism formula. Ladenburg argued that in Kekulé’s formula the 1, 2-position is different from the the 1, 6-position and the 1, 3-position may be different from the 1, 5-position, whereas experimental evidence supported the identity of these positions. He moved to the University of Kiel in 1872 and, continuing his benzene researches, showed only three disubstitution products of benzene are possible, only one pentachlorobenzene exists, and mesitlene is symmetrical trimethylbenzene. In amassing evidence for the equivalence of the six benzene carbon atoms, Ladenburg recognized that he was weakening support for his prism formula and said in 1875 that there was no symbolic representation of benzence satisfying all requirements. In 1876 he summarized his view on benzene strucuture in Die Theorie der aromatischen Verbindungen, drawing attention to Körner’s method for ascertaining the structure of benzene derivatives.
Ladenburg married Margaret pringsheim, daughter of the professor of botany at Berlin, on 19 September 1876. Soon after, he began the study of alkaloids, concentrating on atropine and its derivatives. In 1884 Ladenburg began the work that resulted in the first synthesis of an alkāloid, coniine. He was the first to show that d, 1-bases can be resolved by Pasteur’s method for resolving d, 1-acids. The acid tartrate was prepared and resolved, the coniine liberated, and the dextrorotatory form identified with naturally occurring coiine.
In 1889 Ladenburg became professor at Breslau, where he continued work o alkaloids and racemic compounds. He ascertained the formula of ozone as O3 and accurately determined the atomic weight of iodine in seeking an answer to the question of its position relative to tellurium in the periodic table.
Ladenburg was a member of the Berlin and Paris academies of sciences. He was an honorary and foreign member of the Chemical Society of London and recipient of the Davy Medal of the Royal Society in 1907.
I. Original Works. Landenburg’s first book was Vorträge über die Entwicklungsgeschichte der Chemie in den letztem hundert Jahren (Brunswick, 1869); there is an English trans. by Leonard Dobbin from the 2nd German ed., Lectures on the History of the Development of Chemistry Since the Time of Lavoisier (Edinburg, 1900). Ladenburg’s Handwörterbuch der Chemie, which he began compiling at Kiel in 1873, was published in 13 vols. (Breslay, 1882–1896). His controversial lecture, “Einfluss der Naturwissenchaften auf die Weltanschauung,” delivered at Kassel, on 21 September 1903, caused bitter feelings between Ladenburg and his friends and colleagues; it was trans. into English by C. T. Sprague as On the Influence of the Natural Science on Our Conceptions of the Universe (London, 1908). His viwes on the nature of reacemic compounds are summarized in Über Racemie (Stuttgart, 1903). Ladenburg wrote a short autobiography toward the end of his life which his son, Rudolph, had published as Lebenserinnerungen (Berslau, 1912). For a complete list of Ladenburg’s publications see W. Herz, “Albert Ladenburg,” in Berichte der Deutschen chemischen Gesellschaft45 (1912), 3636–3644.
II. Secondary Literature. Drawing from Ladenburg’s Lebenserinnerungen, the following papers present comprehensive accounts of Landenburg’s life and work: F. S. Kipping, “Ladenburg Memorial Lecture,” in Journal of the Chemical Society, 103 (1913), 1871–1895; and W. Herz, “Albert Ladenburg,” in Berichte der Deutschen chemischen Gesellschaft, 45 (1912), 3597–3644. See also M. Delépine, ed., La synthèse totale en chimie organique (Paris, 1937), pp. 130–143, for memoirs of Ladenburg and others.
A. Albert Baker, Jr.
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