Meyer, Victor

MEYER, VICTOR

(b Berlin, Germany, 8 September 1848; d. Heidelberg, Germany, 8 August 1897)

chemistry.

Victor Meyer was the second son of Jacques and Bertha Meyer. The elder Meyer, a prosperous Jewish merchant in calico printing and dyeing, wanted his sons to become chemists, but Victor’s foremost desire was to be an actor. Hoping that his interests would change, the family persuaded him to attend some lectures at Heidelberg, where his brother Richard was a student. He then enrolled at Berlin and transferred to Heidelberg in 1865. He was suddenly converted to chemistry on encountering the renowned Bunsen. His dramatic gifts were to be employed as a striking and effective teacher.

At Heidelberg, Meyer studied under Bunsen, Erlenmeyer, Kopp, Kirchhoff, and Helmholtz. He headed the lists in all his courses and progressed so rapidly that he was awarded the Ph.D., summa cum laude, at the age of eighteen.

Bunsen was so impressed with Meyer that he immediately selected him to be his assistant. Meyer worked with Bunsen for one year, performing analyses of the mineral waters of Baden for the government. Bunsen then recommended him io Baeyer, whose laboratory at the Gewerbeakademie in Berlin was one of the most famous in luropc. Meyer spent three years with Baeyer (1868–1871), beginning his publications in organic chemistry during this period. His first professorship was at the Stuttgart Polytechnic in 1871. At the age of twenty-four he became a full professor and director of the chemical laboratories at the Eidgenössische Technische Hochschule at Zurich. Meyer celebrated this appointment with his engagement io Hedwig Davidson. They were married in 1873 and had live daughters.

Meyer had rejected offers from several institutions during his thirteen years in Zurich, when in 1885 the university of Göttingen asked him to take charge of the construction of its new chemical laboratories. No sooner were the laboratories completed in 1888 than Meyer received the offer of Bunsen’s chair at Heidelberg. He felt obliged to remain at Göttingen and declined the offer. It was only Bunsen himself, intervening with the Prussian ministry for the release of Meyer from Göttingen, who enabled Meyer to become his successor at Heidelberg, a position Meyer held until his death in 1897.

An extremely attractive personality, Meyer was also a brilliant lecturer and attracted many students from both Europe and North America. He was a member of the academies of Berlin, Uppsala, and Göttingen, and president of the German Chemical Society.

Meyer’s health declined during the 1880’s. He suffered several breakdowns and was so frequently ill that he resorted to drugs in order to sleep. He became conscious that his long suffering was affecting his thinking and suddenly in the summer of 1897, suffering from continuous neuralgic pains, his nervous system shattered, he ended his life by taking prussic acid.

There is an unusually large number of important contributions in the more than 300 papers that Meyer published. His first significant paper appeared in 1870, when he described a new method for introducing the carboxyl group into an aromatic substance by heating the potassium salts of aromatic sulfonic acids with sodium formate. This method has been used ever since by organic chemists for the synthesis of aromatic acids. Meyer’s primary purpose in this paper was to ascertain the constitution of benzene derivatives. The determination of the ring position of substituents in isomeric aromatic compounds was an unsettled problem, and Meyer established that salicylic acid and other compounds which had been assigned to the meta series were ortho derivatives, In a paper one year later Meyer listed many disuhstituted benzoic acids in columns according to whether they were ortho, meta, or para compounds.

Meyer first attracted wide attention in 1872 with his work on the nitroparaffins. Aromatic nitro compounds were well known and easily prepared from aromatic hydrocarbons, but aliphatic nitro compounds existed only in scattered examples, obtained mostly by accident. Meyer proposed the existence of two series of isomeric organic nitrogen compounds: the nitrite and nitro compounds. During his year at Stuttgart, he discovered a general method for the preparation of nitroparallins and made the subject his main research problem for his first four years at Zurich. Meyer found that alkyl iodides combined with silver nitrite to form true nitro compounds, the nitrogen atom being bound directly to a carbon atom, whereas the isomeric nitrites were esters. He explored this area so thoroughly that at the time of his death almost all that was known about nitro compounds was due to Meyer and his students.

Meyer disclosed the existence of two new classes of organic nitrogen substances from the surprising reactions of nitrous acid with the primary and secondary nitroparaffins. Primary nitro compounds formed acidic products which dissolved in alkali to form red salts. Secondary nitro compounds formed blue nonacidic products which did not dissolve in alkali. Meyer named these products “nitrolic acids” and “pseudonitrotes” respectively. Since tertiary nitroparaffins did not react with nitrous acid, these color reactions served as a test to differentiate between primary, secondary, and tertiary radicals. Meyer and his students established the structural formulas for the nitrolic acids and pseudonitroles.

Meyer then explored a variety of organic nitrogen compounds and discovered several new types. His most important compound was his preparation of the first oximes by means of the reaction between hydroxylamine and an aldehyde or ketone. He proved that this was a general reaction with the carbonyl group, and he established the structure of oximes.

Victor Meyer’s name is most closely associated with his vapor density method. Devised in three stages from 1876, the method was a product of his researches in organic chemistry, since it was necessary for him to determine the molecular formulas of the substances with which he was working. There were several methods available for determining the density of the vapors of liquids or solids, each having particular advantages and disadvantages. Meyer wanted a method that (1) utilized small amounts of a substance (he was working with new substances usually obtainable only in small quantities) and that (2) could be used at high temperatures (his substances often possessed high boiling points).

In 1876 he measured for the first time the vapor density of diphenyl, anthracene, anthraquinone, triphenylamine, p -dibromobenzene, and p -diphenylbenzene by volatilizing them at the temperature of boiling sulfur. The following year, in order to make his method more flexible, he used the vapors of a variety of liquids, depending on the temperature required, instead of sulfur. Finally, in 1878 he presented his third and best-known modification. The vapor of a weighed substance displaced an equal volume of air, which in turn was measured by means of a burette. This method is more commonly used than any other, and Meyer’s apparatus is found in most chemical laboratories.

These vapor density studies led to his endless series of pyrochemical researches, which he investigated until his last days at Heidelberg. Meyer hoped to get vapor density estimations at ever higher temperatures. He employed molten lead baths and platinum, platinum-iridium, and porcelain bulbs, which enabled him to study vapors at temperatures up to 3000° C. Very little was known about the molecular constitution of vapors at high temperatures. Meyer’s method made possible the determination of the molecular state of many elements and inorganic substances. In 1879 he showed that the halogens dissociated at high temperatures. His pyrochemical investigations included vapor density determinations, the effect of temperature on the dissociation of substances, and the study of the ignition temperatures of explosive gas mixtures. In 1885 he published Pyrochemische Untersuchungen, a monograph on the subject.

A new area for investigation came about through a lecture demonstration that failed. In 1882 Meyer gave a series of lectures on benzene and its derivatives. His lectures were brilliant as usual, and the experiments performed before the class were well prepared. At one of these lectures Meyer wanted to show the students Baeyer’s indophenine test for benzene, in which the addition of isatin and sulfuric acid to benzene produces the deep blue indophenine. The results were negative. Sandmeyer, Meyer’s assistant, reminded him afterward that the benzene sample that had been used was not commercial benzene from coal tar but synthetic benzene prepared by the decarboxylation of benzoic acid.

Meyer’s investigation of the indophenine reaction began the same day. He found that the purest samples of benzene from coal tar invariably gave the blue color reaction, but the color could be eliminated by first extracting the benzene with sulfuric acid. The sulfonated product on distillation gave Meyer an active “benzene,” which again showed the indophenine reaction. Meyer proposed several hypotheses, one of which was that coal-tar benzene was a mixture of two substances with similar properties and that only one of these substances combined with isatin. In 1883 he isolated this substance and named it “thiophene” because it contains sulfur and is similar to phenyl compounds. He then rapidly developed the subject and was able in five years to publish a 300-page monograph. Die Thiophengruppe (1888), which contains a list of 106 papers by Meyer and his students. His main interest was in demonstrating the similarity between the chemistry of thiophene compounds and the chemistry of benzene. By 1885 he proved that thiophene has a ring structure and suggested that pyrrole and furan were analogous ring compounds.

Meyer contributed many papers on the negative nature of radicals, a topic which had interested him ever since he detected the acidic properties of the nitroparaffins. He could replace hydrogen in a nitroparaffin by an alkali metal and thereby form a salt. He explained that the acidic character is due to the influence of the nitro group on the hydrogen atoms bound to the same carbon atom. He noted that acidity can be induced in an inert hydrocarbon by the introduction of certain substituents, such as nitro, cyano, or phenyl radicals. In 1887 Meyer defined those groups which possessed acid-inducing properties as “negative,” later termed “electrophilic” by Ingold in the context of the electronic theory of valence.

Continuing research on the oximes led Meyer into the realm of stereochemistry and the spatial effects of radicals. Meyer and his students noted that benzil forms more than one dioxime. In 1888 he and Karl von Auwers explained that the isomerism is due to lack of free rotation about the carbon-carbon single bond, an explanation at variance with van’t Hoff’s assumption of free rotation about such bonds. In so doing, they proposed the term “stereochemistry” in place of van’l Hoff’s “chemistry in space” as a more suitable name for phenomena involving spatial effects. Their explanation never appealed to chemists, and Hantzsch and Werner in 1890 presented an explanation based on the stereochemistry of nitrogen. This explanation proved to be more satisfactory, although Meyer was critical to the end of his life of their spatial formulas.

Meyer’s interest in spatial aspects of organic reactions continued during the 1890’s, and in 1894 he identified the inhibiting effect known as “steric hindrance.” Benzoic acid and most of its substitution products readily formed esters with alcohol at room temperature, but Meyer observed that trisubstituted benzoic acids do not form esters unless the carboxyl group is extended well beyond the ring by the interposition of a chain of carbon atoms. Further study showed that meta and para derivatives of benzoic acid esterify almost completely while their isomeric diortho compounds yield little or no ester. Meyer explained this as a spatial effect, the ortho substituent exerting a blocking action, which suppresses the esterification.

Concurrently with his stereochemical researches, Meyer published many papers exploring new types of aromatic iodine compounds. He revealed that iodine can exist in higher oxidation states in aromatic compounds. He first prepared an “iodoso” compound in 1892 by the oxidation of o -iodobenzoic acid; further oxidation produced an “iodoxv” compound. What was remarkable to him was his discovery in 1894 of a class of free organic bases, the “iodonium” compounds. He obtained the first member of this class by the interaction of iodoso- and iodoxyhydrocarbons. Iodosobenzene and iodoxybenzene yielded diphenyliodonium hydroxide:

C₆H₅—IO + C₆H₅—IO₂ + AgOH

→ (C₆H₅)₂I—OH + AgIO₃

Iodonium hydroxides are strong bases resembling the quaternary ammonium and ternary sulfonium bases.

Victor Meyer’s concern for excellence in teaching found expression in a project with which he was occupied at the time of his death. With Paul Jacobson, his assistant at Heidelberg, he wrote a comprehensive treatise on organic chemistry, the Lehrbuch der organischen Chemie. This two-volume work, the second volume of which was incomplete when he died, remains the best extended treatment of the subject. The book was meant to be fresh and comprehensive. It included the most recent developments in theory, the authors being the first to use stereochemistry as a background for the subject. Written in an attractive style, it remains a rich source of information about both the principles of organic chemistry and of the chemistry of the classes of organic compounds and their individual members.

BIBLIOGRAPHY

I. Original Works. Meyer wrote three major chemical treatises: Pyrochemische Untersuchungen (Brunswick, 1885), written with Carl Langer; Die Thiophengruppe (Brunswick, 1888); and Lehrbuch der organischen Chemie, 2 vols. (Leipzig, 1893–1903), written with Paul Jacobson.

Among his important papers are “Untersuchungen über die Constitution der zweifach-substituirten Benzole, “in Justus Liebigs Annalen der Chemie, 156 (1870), 265–301, and 159 (1871), 1–27; “Über die Nitroverbindungen der Fettreihe,” in Berichte der Deutschen chemischen Gesell schaft, 5 (1872), 399–406, 514–518, writtenwith O. Stüber; “Über die Nitroverbindungen der Fettreihe,” in Justus Liebigs Annalen der Chemie, 171 (1874), 1–56, and 175 (1875), 88–140; “Über die Pseudonitrole, die Isomeren der Nitrolsäuren” ibid., 180 (1876), 133–155, written with J. Locher; “Zur Dampfdichtebestimmung,” in Berichte der Deutschen chemischen Gesellschaft, 11 (1878), 1867–1870; “Über das Verhalten des Chlors bei höher Temperatur,” idid., 12 (1879), 1426–1431, written with Carl Meyer; “Über stickstoffhaltige Acetonderivate,” ibid., 15 (1882), 1164–1167, written with Alois Janny; “Untersuchungen über die Strukturformel des Thiophens,” ibid., 18 (1885), 3005–3012, written with L. Gattermann and A. Kaiser; “Untersuchungen Über die zweite van’t Hoffsche Hypothese,” ibid., 21 (1888), 784–817, and “ür die isomeren Oxime unsymmetrischer Ketone und die Configuration der Hydroxylamins,” ibid., 23 (1890), 2403- 2409, written with Karl Auwers; “Über Jodosobenzoësäure,"ibid., 25 (1892), 2632–2635, written with Wilhelm Wachter; “Über ein seltsames Gesetz bei der Esterbildung aromatischer Säuren,” ibid., 27 (1894), 510–512; “Das Gesetz der Esterbildung aromatischer Säuren,” ibid., 1580–1592, and “Weiteres Über die Esterbildung aromatischer Säuren,” ibid., 3146–3156, written with J. Sudborough.

II. Secondary Literature. The principal source on the life and work of Victor Meyer was composed by his brother Richard Meyer: Victor Meyer. Leben und Wirken eines deutschen Chemikers und Naturforschers 1848–1897 (Leipzig, 1917).

Other important studies are Heinrich Biltz, in Zeitschrift für anorganische Chemie, 16 (1898), 1–14; Margaret Davis Cameron, “Victor Meyer and the Thiophene Compounds,” in Journal of Chemical Education, 26 (1949), 521–524; Friedrich Challenger, “Victor Meyer’s and Paul Jacobson’s ’Lehrbuch der organischen Chemie’: the Authors and Their Work,” in Journal of the Royal Institute of Chemistry, 82 (1958), 164–169; Benjamin Harrow, Eminent Chemists of Our Time, 2nd ed. (New York, 1927), 177–195, 407–422; F. Henrich, in G. Bugge, ed., Das Buch der grossen Chemiker, II (Berlin, 1930), 374–390; B. Horowitz, in Journal of the Franklin Institute, 182 (1916), 363–394; Paul Jacobson, in Allgemeine Deutsche Biographie, LV (Leipzig, 1910), 833–841; and C. Liebermann, in Berichte der Deutschen chemischen Gesellschaft 30 (1897), 2157–2168.

See also G. Lunge, in Vierteljahrsschrift der Naturforschenden Gesellschaft in Zürich, 42 (1897), 347–361; J. McCrae, “Recollections of Heidelberg and Victor Meyer: 1893–1895,” in Journal of the Royal Institute of Chemistry, 82 (1958), 77–82; Richard Meyer, in Berichte der Deutschen chemischen Gesellschaft, 41 (1909), 4505–4718; Gustav Schmidt, “The Discovery of the Nitroparaffins by Victor Mayer,” in Journal of Chemical Education, 27 (1950), 557–559; J. Sudborough, “Victor Meyer,” in Proceedings of the Chemical Society (1959), 137–141; and Edward Thorpe, Essays in Historical Chemistry, 3rd ed. (London, 1911), 422–482, which originally appeared as the “Victor Mover Memorial lecture,” in Journal of the Chemical Society, 77 (1900), 169–206.

Albert B. Costa