Auguste Laurent

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Auguste Laurent

Auguste Laurent (born November 14, 1807 in the La Folie district of the municipality of Saint-Maurice near Langres , † April 15, 1853 in Paris ), actually Augustin Laurent , was a French chemist . Laurent was an organic chemist, he established the core theory for substitution in organic chemistry . He defined the terms molecule , atom and chemical equivalent for organic chemistry. He realized that the number of hydrogen atoms in organic compounds is always even without nitrogen, and always odd with a nitrogen atom in the molecule.

Life

He was born the second of four children to the farmer Jean-Baptiste Laurent and Marie-Jeanne Maistre. In Gray (Haute-Saône) he received a classical school education at one of the local colleges . From December 9, 1826 to 1829 he was trained at the École des Mines , in June 1830 he was civil engineer des mines , in 1831 répétiteur at the École Centrale des Arts et Métiers . His first scientific publication appeared in 1830, written together with Guy-Adolphe Arrault (1806–1861): Fabrication du smalt ou bleu de cobalt, à Querbach, en Basse-Silésie . This work also presents experiences about cobalt mining that he gained during a trip through Lower Silesia .

He was a student of the chemist Jean-Baptiste Dumas . After a dispute with Dumas, he worked in the Manufacture de Sévres in 1833 and in a porcelain factory in Eich ( Luxembourg ) in 1836 . In 1838 he was appointed professor at the University of Bordeaux . In 1839 he married Anne-Françoise Schrobilgen from a well-known Luxembourg family. Her son was Matthieu Paul Hermann Laurent (1841–1908). In 1844 he was made a Knight of the Legion of Honor.

After student unrest he left Bordeaux in 1845 (his successor as professor was his assistant Alexandre Édouard Baudrimont ) and received a position in the Mint of Paris (1848). Together with the chemist Charles Gerhardt (1816–1856), he founded a teaching laboratory for chemistry in Paris in 1851 . Since 1845 he was a corresponding member of the Académie des sciences .

Auguste Laurent died of tuberculosis in 1853 at the age of 45.

Bust of Auguste Laurent on the city wall of Langres

His son was the mathematician Hermann Laurent .

Scientific work

Syntheses and analyzes

Laurent examined the naphthalene together with Dumas . Its molecular formula (C 10 H 8 or C 20 H 16 ) could be determined from the elemental analysis. Determinations of chrysene and pyrene were made later .

Naphthalene could be converted into chloronaphthalene with chlorine. Since structural formulas were still unknown in chemistry, Laurent could only prove that a hydrogen atom was replaced by a chlorine atom. Naphthalene tetrachloride could also be produced by treatment with chlorine. By oxidizing this substance with nitric acid, he produced phthalic acid as well as phthalimide and phthalic anhydride (1836).

Laurent obtained anthraquinone from anthracene by oxidation with nitric acid (1835). In 1841 he obtained isatin from the oxidation of the dye indigo . Ethanol and diethyl ether exemplified Laurent as organic derivatives of water. If a hydrogen atom in water is formally replaced by an ethyl group, ethanol is obtained; if two hydrogen atoms are replaced by ethyl groups, diethyl ether is obtained.

Atoms, molecules, equivalents

Laurent recognized that the number of hydrogen atoms in an organic molecule is always even as long as there is no nitrogen present.

When Laurent began his research, there was still no clear distinction between atom, molecule, equivalent. Charles Gerhardt recognized the flawed atomic masses in light of Avogadro's theory for organic molecules. However, Gerhardt's concept of the equivalent remained very unclear and controversial. Laurent improved Gerhardt's findings and for the first time gave an exact definition for molecules , atoms and equivalents.

Laurent understood the molecular weight of an element or a compound to be the amount by weight that would occupy the same gas space under the same conditions. For gases of the elements hydrogen , chlorine , oxygen and nitrogen , two parts by weight (double atoms) had to be added in the gas space. This resulted in the correct molecular weights for organic molecules in the gas space.

For Laurent, the molecule was the smallest amount necessary to form a chemical compound. For him the atom was the smallest amount of an element that occurs in composite materials.

It was not until 1850, when Alexander William Williamson produced an ether preparation from ethanol and ethyl bromide, that it was possible to prove that ether is a derivative of ethanol and ethanol is a derivative of water.

Laurent and Gerhardt's ideas found their way into books and magazines.

Core theory

Since the conversion of hydrocarbons such as naphthalene or anthracene usually did not change the basic carbon structure and only the hydrogen atoms were replaced by chlorine or oxygen, Laurent formulated the core theory to explain the spatial structure of organic compounds. Dumas was able to prove with candle wax that hydrogen atoms can be replaced by chlorine atoms. Together with Justus von Liebig, he coined the term radical substitution.

Laurent used the term “radical” for atomic nuclei. Later he also used it for larger groups of atoms. In organic molecules, unlike in inorganic chemistry, there are stem nuclei of carbon atoms. The carbon parent nuclei are spatially ordered and can accommodate secondary nuclei of hydrogen, chlorine or oxygen atoms according to geometrical and stoichiometric laws. Only a few specific secondary nuclei in the molecule can split off and form a radical.

Laurent suspected that stem nuclei could be in the center of a pyramid, on the edges of the pyramid there are secondary nuclei such as hydrogen, oxygen and halogen atoms which can be exchanged under certain reaction conditions. This is the core theory (chemistry) .

Works (selection)

  • Laurent, Auguste; Arrault, Guy-Adolphe: Fabrication du smalt ou bleu de cobalt, à Querbach, en Basse-Silésie. Annales de l'Industrie Francaise et Étrangère et Bulletin de l'École Centrale des Arts et Manufacture, (1830), p.474

literature

  • Marika Blondel-Megrelis: Dire les choses. Auguste Laurent et la méthode chimique , Vrin, 2000, ISBN 2-7116-8300-1
  • Günther Bugge: The book The Great Chemist , Verlag Chemie, Weinheim 1974, Prof. Max Bloch: Gerhardt and Laurent , p. 92 ff. ISBN 3-527-25021-2
  • Georg Lockemann: History of Chemistry - From the Discovery of Oxygen to the Present , Walter de Gruyter & Co., Berlin 1955, p. 59

Web links

Individual evidence

  1. ↑ Biography in English of Sathis C. Kapoor (2009)
  2. ↑ Genealogy G.-A. Arrault
  3. ↑ Satish C. Kapoor: The Origins of Laurent's Organic Classification . In: Isis . tape 60 , no. 4 , 1969, p. 477-527 , JSTOR : 229107 .
  4. ↑ biography of the son
  5. ^ List of members since 1666: Letter L. Académie des sciences, accessed on January 9, 2020 (French).
  6. ↑ Annales de Chimie et de Physique (3), 18 , 266
  7. ^ August Kekulé, Richard Anschütz, Gustav Schultz, Wilhelm LaCoste: Textbook of organic chemistry, or, The chemistry of carbon compounds . F. Enke, Erlangen 1861, OCLC 494072095 , p. 66 ( limited preview in Google Book search).
personal data
SURNAME Laurent, Auguste
BRIEF DESCRIPTION French chemist
DATE OF BIRTH November 14, 1807
PLACE OF BIRTH Langres
DATE OF DEATH April 15, 1853
Place of death Paris