1840-1850
When studying a set of molecular formulas Laurent discovered (1846) great similarities between them. Thus, he established that ethanol and ethyl ether can be considered derivatives of water by replacing one or two of its hydrogens with ethyl radicals (until that time alcohols were mistakenly considered ether hydrates and their formula was believed to be R2O.H2O instead of ROH). Molecules begin to be classified by type (e.g., water type molecule). This point is considered the definitive break with Berzelius' dualistic theory and the beginning of the modern formulation. In 1848 Kolbe and Frankland showed that acetic acid could be obtained by treating methyl cyanide with dilute acids or bases. It was thus concluded that acetic acid should contain a methyl group.
Hermann Kolbe (1818-1884): Professor of Chemistry at Marburg and Leipzig in Germany. He carried out extensive research in organic chemistry and made significant theoretical contributions, particularly in the study of organic radicals and their significance in the construction of molecules.
Edward Frankland (1825-1899): Professor of Chemistry in Manchester and London. He carried out studies on carboxylic acids, nitriles and organometallic compounds. With Lockyer he discovered helium in the sun.
In 1849 Wurtz and Hofmann established a new type of molecules, those derived from ammonia. Hofmann develops methods for obtaining amines and ammonium salts. The degradation reaction of the latter is named after him.
Charles Adolphe Wurtz (1817-1884): Professor of Organic Chemistry in Paris. He was a student of Dumas and Liebig; Couper, van 't Hoff and Le Bel studied in his laboratory. Wurtz investigated phosphorus and nitrogen compounds, discovered the reaction that bears his name, between alkyl halides and sodium to form alkanes, and established the formulas of glycerin and glycol.
August Wilhelm von Hofmann (1818-1892): Liebig's student who was a professor of Chemistry for more than twenty years in London. He founded the German Chemical Society. He discovered a general method of preparing amines. He isolated benzene and aniline from coal tar; with Fritzche he carried out the synthesis of aniline, and was one of the creators of the aniline dye industry.