Moses Gomberg

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Moses Gomberg
Gombergm01.jpg
Moses Gomberg, the father of radical chemistry
Born(1866-02-08)February 8, 1866
DiedFebruary 12, 1947(1947-02-12) (aged 81)
Ann Arbor, Michigan, United States
Alma mater University of Michigan
Known for Radical chemistry
Awards Willard Gibbs Award (1925)
Scientific career
Fields chemistry
Institutions University of Michigan
Doctoral advisor A. B. Prescott

Moses Gomberg (February 8, 1866 – February 12, 1947) was a chemistry professor at the University of Michigan. [1]

Chemist Scientist trained in the study of chemistry

A chemist is a scientist trained in the study of chemistry. Chemists study the composition of matter and its properties. Chemists carefully describe the properties they study in terms of quantities, with detail on the level of molecules and their component atoms. Chemists carefully measure substance proportions, reaction rates, and other chemical properties. The word 'chemist' is also used to address Pharmacists in Commonwealth English.

University of Michigan Public research university in Ann Arbor, Michigan, United States

The University of Michigan, often simply referred to as Michigan, is a public research university in Ann Arbor, Michigan. The university is Michigan's oldest; it was founded in 1817 in Detroit, as the Catholepistemiad, or University of Michigania, 20 years before the territory became a state. The school was moved to Ann Arbor in 1837 onto 40 acres (16 ha) of what is now known as Central Campus. Since its establishment in Ann Arbor, the university campus has expanded to include more than 584 major buildings with a combined area of more than 34 million gross square feet spread out over a Central Campus and North Campus, two regional campuses in Flint and Dearborn, and a Center in Detroit. The university is a founding member of the Association of American Universities.

Contents

Early life and education

He was born in Yelisavetgrad, Russian Empire. His parents were the son of a merchant, Hershko (Hirsh) Gomberg and Maryam-Ethel nee Reznikova. In 1884, the family emigrated to Chicago to escape the pogroms following the assassination of Czar Alexander II. In Chicago he worked at the Stock Yards while attending Lake High School. In 1886, Moses entered the University of Michigan, where he obtained his B.Sc in 1890 and his doctorate in 1894 under the supervision of A. B. Prescott. His thesis, titled "Trimethylxanthine and Some of its Derivatives", dealt with the derivatization of caffeine. [2]

Russian Empire Former country, 1721–1917

The Russian Empire, also known as Imperial Russia or simply Russia, was an empire that existed across Eurasia and North America from 1721, following the end of the Great Northern War, until the Republic was proclaimed by the Provisional Government that took power after the February Revolution of 1917.

Chicago City in Illinois, United States

Chicago, officially the City of Chicago, is the most populous city in Illinois, as well as the third most populous city in the United States. With an estimated population of 2,716,450 (2017), it is the most populous city in the Midwest. Chicago is the principal city of the Chicago metropolitan area, often referred to as Chicagoland, and the county seat of Cook County, the second most populous county in the United States. The metropolitan area, at nearly 10 million people, is the third-largest in the United States, and the fourth largest in North America and the third largest metropolitan area in the world by land area.

Pogrom The deliberate persecution of an ethnic or religious group either approved or conducted by the local authorities

A pogrom is a violent riot aimed at the massacre or persecution of an ethnic or religious group, particularly one aimed at Jews. The Russian term originally entered the English language in order to describe 19th and 20th century attacks on Jews in the Russian Empire. Similar attacks against Jews at other times and places also became retrospectively known as pogroms. The word is now also sometimes used to describe publicly sanctioned purgative attacks against non-Jewish ethnic or religious groups. The characteristics of a pogrom vary widely, depending on the specific incidents, at times leading to, or culminating in, massacres.

Career

Gomberg in the chemistry lab MGyoung.JPG
Gomberg in the chemistry lab
University of Michigan Chemistry Building MGLab.JPG
University of Michigan Chemistry Building

Appointed an instructor in 1893, Gomberg worked at the University of Michigan for the duration of his professional academic career, becoming chair of the Department of Chemistry from 1927 until his retirement in 1936. Dr. Gomberg served as President of the American Chemical Society in 1931.

In 1896–1897, he took a year's leave to work as a postdoctoral researcher with Baeyer and Thiele in Munich and with Victor Meyer in Heidelberg, where he successfully prepared the long-elusive tetraphenylmethane.

A postdoctoral researcher or postdoc is a person professionally conducting research after the completion of their doctoral studies. The ultimate goal of a postdoctoral research position is to pursue additional research, training, or teaching in order to have better skills to pursue a career in academia, research, or any other fields. Postdocs often, but not always, have a temporary academic appointment, sometimes in preparation for an academic faculty position. They continue their studies or carry out research and further increase expertise in a specialist subject, including integrating a team and acquiring novel skills and research methods. Postdoctoral research is often considered essential while advancing the scholarly mission of the host institution; it is expected to produce relevant publications in peer-reviewed academic journals or conferences. In some countries, postdoctoral research may lead to further formal qualifications or certification, while in other countries it does not.

Adolf von Baeyer German Chemist

Johann Friedrich Wilhelm Adolf von Baeyer was a German chemist who synthesised indigo, developed a nomenclature for cyclic compounds. He was ennobled in the Kingdom of Bavaria in 1885 and was the 1905 recipient of the Nobel Prize in Chemistry.

Johannes Thiele (chemist) German chemist

Friedrich Karl Johannes Thiele was a German chemist and a prominent professor at several universities, including those in Munich and Strasbourg. He developed many laboratory techniques related to isolation of organic compounds. In 1907 he described a device for the accurate determination of melting points, since named Thiele tube after him.

During attempts to prepare the even more sterically congested hydrocarbon hexaphenylethane, he correctly identified the triphenylmethyl radical, the first persistent radical to be discovered, and is thus known as the founder of radical chemistry. The work was later followed up by Wilhelm Schlenk. Gomberg was a mentor to Werner Emmanuel Bachmann who also carried on his work and together they discovered the Gomberg-Bachmann reaction. [3] In 1923, he claimed to have synthesized chlorine tetroxide via the reaction of silver perchlorate with iodine, but was later shown to have been mistaken.

Steric effects

Steric effects are nonbonding interactions that influence the shape (conformation) and reactivity of ions and molecules. Steric effects complement electronic effects, which usually dictate shape and reactivity. Steric effects result from repulsive forces between overlapping electron clouds. Steric effects are widely exploited in applied and academic chemistry.

Hexaphenylethane chemical compound

Hexaphenylethane is a hypothetical organic compound consisting of an ethane core with six phenyl substituents. All attempts at its synthesis have been unsuccessful. The trityl free radical, Ph3C, was originally thought to dimerize to form hexaphenylethane. However, an inspection of the NMR spectrum of this dimer reveals that it is in fact a non-symmetrical species rather than hexaphenylethane, due to the severe steric repulsions that hexaphenylethane would experience. However, paradoxically, a substituted derivative of hexaphenylethane, hexakis(3,5-di-t-butylphenyl)ethane, has been prepared and features a very long central C–C bond at 167 pm (compared to the typical bond length of 154 pm). Attractive London dispersion forces between the t-butyl substituents are believed to be responsible for the stability of this very hindered molecule.

Triphenylmethyl radical chemical compound

The triphenylmethyl radical is a persistent radical and the first radical ever described in organic chemistry. It can be prepared by homolysis of triphenylmethyl chloride 1 by a metal like silver or zinc in benzene or diethyl ether. The radical 2 forms a chemical equilibrium with the quinoid type dimer 3 (3-triphenylmethyl-6-diphenylmethylidene-1,4-cyclohexadiene). In benzene the concentration of the radical is 2%.

Synthesis of tetraphenylmethane

Gomberg was the first to successfully synthesize tetraphenylmethane. This was accomplished by the thermal decomposition of 1-phenyl-2-trityldiazene to the desired product in 2-5% yield. [4] [5]

Tetraphenylmethane chemical compound

Tetraphenylmethane is an organic compound consisting of a methane core with four phenyl substituents. It was first synthesized by Moses Gomberg in 1898.

Tetraphenylmethane synthesis.svg

Discovery of persistent radicals

Trivalent carbon synthesis.svg

Seeking to prepare hexaphenylethane (5), Gomberg attempted a Wurtz coupling of triphenylmethyl chloride (1). Elemental analysis of the resultant white crystalline solid, however, uncovered discrepancies with the predicted molecular formula:

Triphenylmethyl chloride chemical compound

Triphenylmethyl chloride or trityl chloride (TrCl) is a white solid with the chemical formula C19H15Cl. It is an alkyl halide, sometimes used to introduce the trityl protecting group.

Elemental analysis

Elemental analysis is a process where a sample of some material is analyzed for its elemental and sometimes isotopic composition. Elemental analysis can be qualitative, and it can be quantitative. Elemental analysis falls within the ambit of analytical chemistry, the set of instruments involved in deciphering the chemical nature of our world.

calculated for (5)found
% Carbon93.8387.93
% Hydrogen6.176.04

Hypothesizing that (1) had combined with molecular oxygen to form the peroxide (4), Gomberg found that treatment of (1) with sodium peroxide was another means of synthesizing (4).

By performing the reaction of triphenylchloromethane with zinc under an atmosphere of carbon dioxide Gomberg obtained the free radical (2). This compound reacted readily with air, chlorine, bromine and iodine. On the basis of his experimental evidence Gomberg concluded that he had discovered the first instance of a persistent radical and trivalent carbon. This was a controversial conclusion for many years as molecular weight determinations of (2) found a value that was double that of the free radical. Gomberg postulated that some non-tetravalent carbon structure existed in solution because of the observed activity towards oxygen and the halogens. [6] Gomberg and Bachmann later found that treatment of "hexaphenylethane" with magnesium resulted in a Grignard reagent, the first instance of the formation of such a compound from a hydrocarbon. [7] Studies of other triarylmethyl compounds gave results similar to Gomberg's, and it was hypothesized that (2) existed in equilibrium with its dimer hexaphenylethane (5). [8] However this structure was later disproven in favor of the quinoid dimer (3). [9] [10] [11] [12]

At the end of his first report of trivalent carbon "On Trivalent Carbon" [8] Gomberg wrote "This work will be continued and I wish to reserve the field for myself." While nineteenth-century chemists respected such claims Gomberg found that the field of chemistry he founded was too rich to reserve for himself.

Legacy

Plaque commemorating the discovery of organic radicals Moses Gomberg plaque.jpg
Plaque commemorating the discovery of organic radicals

Upon his death in 1947 Moses Gomberg bequeathed his estate to the Chemistry Department of the University of Michigan for the creation of student fellowships. In 2000, the centennial of his paper "Triphenylmethyl, a Case of Trivalent Carbon", a symposium was held in his memory and a plaque was installed in the Chemistry Building at the University of Michigan designating a National Historic Chemical Landmark.

In 1993, the Chemistry Department of the University of Michigan instituted the Moses Gomberg Lecture series to provide assistant professors an opportunity to invite distinguished scientists to the Chemistry department.

Personal life

Gomberg never married, living with his sister Sophia in Ann Arbor for his adult life. [13]

Related Research Articles

A carbanion is an anion in which carbon is trivalent (forms three bonds) and bears a formal negative charge in at least one significant mesomeric contributor (resonance form). Absent π delocalization, carbanions assume a trigonal pyramidal, bent, or linear geometry when the carbanionic carbon is bound to three (e.g., methyl anion), two (e.g., phenyl anion), or one (e.g., acetylide anion) substituents, respectively. Formally, a carbanion is the conjugate base of a carbon acid:

Werner Emmanuel Bachmann was an American chemist. Bachmann was born in Detroit, Michigan where he studied chemistry and chemical engineering at Wayne State University and later at the University of Michigan in Ann Arbor nearby. He completed his doctorate under Moses Gomberg and spent the rest of his academic career at the University of Michigan.

Allyl group functional group

An allyl group is a substituent with the structural formula H2C=CH−CH2R, where R is the rest of the molecule. It consists of a methylene bridge (−CH2−) attached to a vinyl group (−CH=CH2). The name is derived from the Latin word for garlic, Allium sativum. In 1844, Theodor Wertheim isolated an allyl derivative from garlic oil and named it "Schwefelallyl". The term allyl applies to many compounds related to H2C=CH−CH2, some of which are of practical or of everyday importance, for example, allyl chloride.

A non-Kekulé molecule is a conjugated hydrocarbon that cannot be assigned a classical Kekulé structure.

Triphenylmethane chemical compound

Triphenylmethane, or triphenyl methane, is the hydrocarbon with the formula (C6H5)3CH. This colorless solid is soluble in nonpolar organic solvents and not in water. Triphenylmethane is the basic skeleton of many synthetic dyes called triarylmethane dyes, many of them are pH indicators, and some display fluorescence. A trityl group in organic chemistry is a triphenylmethyl group Ph3C, e.g. triphenylmethyl chloride (trityl chloride) and the triphenylmethyl radical (trityl radical).

Iodine pentafluoride is an interhalogen compound with chemical formula IF5. It is a fluoride of iodine. It is a colorless or yellow liquid with a density of 3.250 g cm−3. It was first synthesized by Henri Moissan in 1891 by burning solid iodine in fluorine gas. This exothermic reaction is still used to produce iodine pentafluoride, although the reaction conditions have been improved.

Prismane chemical compound

Prismane or 'Ladenburg benzene' is a polycyclic hydrocarbon with the formula C6H6. It is an isomer of benzene, specifically a valence isomer. Prismane is far less stable than benzene. The carbon (and hydrogen) atoms of the prismane molecule are arranged in the shape of a six-atom triangular prism—this compound is the parent and simplest member of the prismanes class of molecules. Albert Ladenburg proposed this structure for the compound now known as benzene. The compound was not synthesized until 1973.

Phenyllithium chemical compound

Phenyllithium or lithobenzene is an organometallic agent with the empirical formula C6H5Li. It is most commonly used as a metalating agent in organic syntheses and a substitute for Grignard reagents for introducing phenyl groups in organic syntheses. Crystalline phenyllithium is colorless; however, solutions of phenyllithium are various shades of brown or red depending on the solvent used and the impurities present in the solute.

Carbenium ion

A carbenium ion is a positive ion with the structure RR′R″C+, that is, a chemical species with a trivalent carbon that bears a +1 formal charge.

The Wurtz–Fittig reaction is the chemical reaction of aryl halides with alkyl halides and sodium metal in the presence of dry ether to give substituted aromatic compounds. Charles Adolphe Wurtz reported what is now known as the Wurtz reaction in 1855, involving the formation of a new carbon-carbon bond by coupling two alkyl halides. Work by Wilhelm Rudolph Fittig in the 1860s extended the approach to the coupling of an alkyl halide with an aryl halide. This modification of the Wurtz reaction is considered a separate process and is named for both scientists.

The Gomberg–Bachmann reaction, named for the Ukrainian-American chemist Moses Gomberg and the American chemist Werner Emmanuel Bachmann, is an aryl-aryl coupling reaction via a diazonium salt.

Cyclobutanetetrone chemical compound

Cyclobutanetetrone, also called tetraoxocyclobutane, is an organic compound with formula C4O4 or (CO)4, the fourfold ketone of cyclobutane. It would be an oxide of carbon, indeed a tetramer of carbon monoxide.

Amino radical chemical compound

The amino radical,
NH
2
, also known as the aminyl radical or azanyl radical, is the neutral form of the amide ion (NH
2
). Aminyl are highly reactive and consequently short lived like most radicals; however, they form an important part of nitrogen chemistry. In sufficiently high concentration, amino radicals dimerise to form hydrazine. While NH2 as a functional group is common in nature, forming a part of many compounds (e.g. the phenethylamines), the radical cannot be isolated in its free form.

Chlorine tetroxide is a chlorine oxide with the chemical formula ClO
4
.

Radical theory is an obsolete scientific theory in chemistry describing the structure of organic compounds. The theory was pioneered by Justus von Liebig, Friedrich Wöhler and Auguste Laurent around 1830 and is not related to the modern understanding of free radicals. In this theory, organic compounds were thought to exist as combinations of radicals that could be exchanged in chemical reactions just as chemical elements could be interchanged in inorganic compounds.

Dennis P. Curran American chemist

Dennis P. Curran is an American organic chemist and a professor of chemistry at University of Pittsburgh known for his research in the fields of organic chemistry, radical chemistry, and fluorous chemistry.

David M. Lemal is the Albert W. Smith Professor of Chemistry Emeritus and Research Professor of Chemistry at Dartmouth College. He received an A.B. degree (summa) from Amherst College in 1955 and a Ph.D. in Chemistry from Harvard University in 1959. At Harvard he worked with R. B. Woodward on deoxy sugars and a synthesis of the alkaloid yohimbine.

The persistent radical effect (PRE) in chemistry describes and explains the selective product formation found in certain free-radical cross-reactions. In these type of reactions, different radicals compete in secondary reactions. The so-called persistent (long-lived) radicals do not self-terminate and only react in cross-couplings. In this way, the cross-coupling products in the product distribution are more prominent.

References

  1. Schoepfle, C.; Bachmann, W. (2004-05-19). "Moses Gomberg 1866-1947". Journal of the American Chemical Society. 69 (12): 2921–2925. doi:10.1021/ja01204a641.
  2. Gomberg, American Chemical Journal (1892) 14 611-19.
  3. Gomberg, M.; Bachmann, W. E. (2002-05-01). "The synthesis of biaryl compounds by means of the diazo reaction". Journal of the American Chemical Society. 46 (10): 2339–2343. doi:10.1021/ja01675a026.
  4. Gomberg, M. (1897-05-01). "Tetraphenylmethan". Berichte der Deutschen Chemischen Gesellschaft. 30 (2): 2043–2047. doi:10.1002/cber.189703002177. ISSN   1099-0682.
  5. Gomberg, M. (2002-05-01). "On Tetraphenylmethane. 1". Journal of the American Chemical Society. 20 (10): 773–780. doi:10.1021/ja02072a009.
  6. Gomberg, M. (2002-05-01). "An instance of Trivalent Carbon: Triphenylmethyl". Journal of the American Chemical Society. 22 (11): 757–771. doi:10.1021/ja02049a006.
  7. Gomberg, Bachmann Journal of the American Chemical Society (1930) 52 2455
  8. 1 2 Gomberg, M. (2002-05-01). "On Trivalent Carbon". Journal of the American Chemical Society. 23 (7): 496–502. doi:10.1021/ja02033a015.
  9. Gomberg, M. (2002-05-01). "On the possible existence of a class of bodies analogous to Triphenylmethyl". Journal of the American Chemical Society. 25 (12): 1274–1277. doi:10.1021/ja02014a009.
  10. Gomberg, Moses (1932-03-01). "A survey of the chemistry of free radicals". Journal of Chemical Education. 9 (3): 439. Bibcode:1932JChEd...9..439G. doi:10.1021/ed009p439.
  11. Lankamp, H.; Nauta, W. Th.; MacLean, C. (1968-01-01). "A new interpretation of the monomer-dimer equilibrium of triphenylmethyl- and alkylsubstituted-diphenyl methyl-radicals in solution". Tetrahedron Letters. 9 (2): 249–254. doi:10.1016/S0040-4039(00)75598-5.
  12. Smith, Michael B.; March, Jerry (2001-01-11). March's Advanced Organic Chemistry: Reactions, Mechanisms, and Structure. Wiley. p. 189. ISBN   9780471585893.
  13. Moses Gomberg in Ann Arbor