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Many textbooks say organic chemistry began when Friedrich Wöhler made urea. The story is more gradual than that, and one of the next steps came from Wöhler's own student, Hermann Kolbe. In 1845 he showed that acetic acid, the acid in vinegar, could be built up from carbon disulphide. This post walks through his route, reads his own words, and checks the numbers he used to prove what he had made.
Who was Hermann Kolbe?
Britannica's biography, written by the historian Alan Rocke, gives his dates as 27 September 1818, Elliehausen near Göttingen, to 25 November 1884, Leipzig. He studied chemistry with Wöhler at Göttingen and took his doctorate with Robert Bunsen at Marburg in 1843. After working in London and as a science editor, he became professor at Marburg in 1851 and later moved to Leipzig, where a new laboratory was built for him. Britannica notes that close to 2,000 students passed through his laboratory classes.
Britannica also credits him with "the first generally accepted synthesis of an organic compound from inorganic materials", published in 1844 to 1845, and says that in the final paper of the series he used the word synthesis in a chemical context for the first time.
What route did Kolbe take to acetic acid?
Kolbe's paper was read to the Chemical Society in London on 7 April 1845 and printed in English as Contributions to the Knowledge of Conjugate Compounds in the Philosophical Magazine; a scanned copy is on the Internet Archive. A German version appeared in Liebig's Annalen der Chemie the same year.
He summarised the chain himself: carbon disulphide, a chloride of carbon, and trichloroacetic acid (which he called "oxalate of chloro-carbon") are the steps that, with the elements of water, lead "from carbon to acetic acid". In modern formulas:
Chlorine reacts with carbon disulphide, CS₂, giving chlorides of sulphur and carbon tetrachloride, CCl₄.
A second chloride of carbon, tetrachloroethene (C₂Cl₄), kept under water with chlorine in sunlight, gives trichloroacetic acid: C₂Cl₄ + Cl₂ + 2H₂O → CCl₃COOH + 3HCl.
Trichloroacetic acid is reduced to acetic acid. Kolbe confirmed Louis Melsens' result that potassium amalgam does this, and found that an electric current with alkali present does it too: CCl₃COOH + 6[H] → CH₃COOH + 3HCl.
Check the balance in step 2. Left side: C 2, Cl 4 + 2 = 6, H 4, O 2. Right side: CCl₃COOH has C 2, H 1, Cl 3, O 2, and 3HCl adds H 3 and Cl 3. Totals: C 2, H 4, Cl 6, O 2. It balances.
His conclusion, in the English text: acetic acid, "which has been until now only known as a product of the oxidation of organic matters, can be also formed synthetically from its elements." Earlier in the paper he writes that these compounds are so similar to organic ones "that it is impossible here to draw a distinct line between organic and inorganic bodies".
Worked example: how Kolbe proved what he had made
To identify trichloroacetic acid, Kolbe analysed its silver salt, CCl₃COOAg. His paper reports that 0.396 g of the salt, heated strongly, left 0.210 g of silver chloride, and that 0.658 g burned with copper oxide gave 0.214 g of carbon dioxide. Use Ag = 107.87, Cl = 35.45, C = 12.01, O = 16.00.
Silver in AgCl: 107.87 ÷ 143.32 = 0.7526. Silver in the sample = 0.210 × 0.7526 = 0.1581 g. Percentage = 0.1581 ÷ 0.396 × 100 ≈ 39.9%.
Carbon in CO₂: 12.01 ÷ 44.01 = 0.2729. Carbon in the sample = 0.214 × 0.2729 = 0.0584 g. Percentage = 0.0584 ÷ 0.658 × 100 ≈ 8.9%.
Theory for CCl₃COOAg: molar mass = 2(12.01) + 3(35.45) + 2(16.00) + 107.87 = 270.24 g/mol. Silver = 107.87 ÷ 270.24 ≈ 39.9%; carbon = 24.02 ÷ 270.24 ≈ 8.9%.
Kolbe wrote that his results corresponded to 39.9% silver and 8.9% carbon, against 40.0 and 8.9 required by the formula. Our check with modern atomic masses agrees.
Common mistakes: forgetting to convert the mass of AgCl to mass of silver, and using the mass of CO₂ as if it were carbon. Always ask what fraction of the weighed product is the element you want.
Why does Kolbe matter beyond this synthesis?
Britannica describes him as one of the leading experimentalists of his century and a major theorist, who also studied the electrolysis of organic acids. It is also frank that he rejected Kekulé's structural formulas and attacked the young van 't Hoff's stereochemistry in 1877, and that by the end of his life many saw him as a crank. Rocke argues that Kolbe held high standards of evidence and thought his rivals were too speculative. Both things were true: he was a careful experimenter who was wrong about structure theory.
For the urea story that came before, read our post on Friedrich Wöhler and urea. For the reactions of acetic acid and its relatives, see our guide to carboxylic acids and their derivatives.
What can a student take from Kolbe's way of working?
Prove the product. Kolbe did not just claim acetic acid; he analysed a salt and compared it with the formula.
Write the chain. He laid out each step from carbon to the acid, which is exactly how you should plan an organic conversion.
Good at experiments does not mean right about everything. Check ideas on evidence, including your own.
If percentage-composition problems still slow you down, the Fermi Problem Library has worked problems with a step-by-step solver that explains the reasoning rather than printing an answer.
Try it now: calculate the percentage of chlorine in CCl₃COOAg and check it against the molar mass above.
