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Textbooks often say that in 1828 Friedrich Wöhler made urea in a flask and so disproved the idea that living things are needed to make organic compounds. The real paper is four pages long, careful and modest, and the story that grew around it is more complicated. This post covers who Wöhler was, what he actually reported, the composition sum at the centre of it, what historians say about the "death of vitalism", and what a student can take from his way of working.
Who was Friedrich Wöhler?
The Science History Institute biography gives his dates as 1800 to 1882. After a medical degree at Heidelberg he went to Sweden to study with Jöns Jakob Berzelius, the leading chemist of the day, and later translated Berzelius's textbook into German. He taught at the University of Göttingen for nearly 50 years and made it a centre for training chemists.
His friendship with Justus von Liebig began in 1825, after the two settled a dispute over cyanic acid and fulminic acid, which seemed to have the same composition but very different properties: silver fulminate explodes and silver cyanate does not. Berzelius called such substances "isomers". Wöhler also extracted aluminium and beryllium from their compounds by chemical means, and with Liebig identified the benzoyl radical in 1832.
What did the 1828 paper report?
The paper, Ueber künstliche Bildung des Harnstoffs (On the artificial formation of urea), appeared in the Annalen der Physik und Chemie in 1828. The original German text can be read in the digitised 1828 volume. Summarised from it:
Wöhler had noticed that whenever he tried to combine cyanic acid with ammonia, for example by treating silver cyanate with ammonium chloride solution or lead cyanate with aqueous ammonia, he got colourless crystals that were not ammonium cyanate.
The crystals released no ammonia when treated with potash or lime, and did not behave like a cyanate with acids or with lead and silver salts.
He compared them with pure urea extracted from urine and found the two "completely identical".
He called the result remarkable because it gave an example of the artificial production of an organic, so-called animal, substance from inorganic substances.
He then closed by declining to draw general conclusions, leaving it to further experience to show what laws might follow from compounds of the same composition with very different properties.
Worked example: same composition, different compound
Urea is CO(NH₂)₂ and ammonium cyanate is NH₄⁺OCN⁻. Both contain one C, four H, two N and one O, so both are CH₄N₂O. Using atomic weights within the CIAAW standard ranges, C = 12.01, H = 1.008, N = 14.01 and O = 16.00:
Molar mass = 12.01 + 4(1.008) + 2(14.01) + 16.00 = 60.06 g/mol, the same for both.
Nitrogen: 28.02 / 60.06 = 46.65%.
Carbon: 12.01 / 60.06 = 20.00%. Oxygen: 16.00 / 60.06 = 26.64%. Hydrogen: 4.032 / 60.06 = 6.71%.
Wöhler's paper quotes William Prout's analysis of urea as 46.650% nitrogen, 19.975% carbon and 26.650% oxygen, almost exactly these values. Analysis alone therefore could not distinguish the two substances. Wöhler had to use their behaviour, such as whether alkali releases ammonia, to show that his crystals were urea. Compounds like these, with one formula and different structures, are isomers.
Common mistakes:
Assuming one formula means one compound. Urea and ammonium cyanate show it does not.
Rounding too early. Keep four significant figures until the end of a percentage calculation.
Confusing empirical and molecular formulas. Here they are the same, but check the molar mass before assuming that.
Did the synthesis really kill vitalism?
The Science History Institute explains the background: organic compounds were thought to come only from living things, so a "vital force" seemed needed to make them. Wöhler's own paper makes no such sweeping claim. Historians have since questioned the textbook story. In 1944 Douglas McKie titled a Nature article Wöhler's 'synthetic' urea and the rejection of vitalism: a chemical legend, and in 2000 Peter Ramberg examined in Ambix how the urea synthesis became tied to organic chemistry's identity. The fair summary is that 1828 was an important early step, and that ideas about a vital force faded gradually rather than ending with one experiment.
What can a student take from how Wöhler worked?
Follow the unexpected result. He was trying to make ammonium cyanate; the crystals that refused to behave were the discovery.
Test identity in several ways. Composition, reactions and direct comparison with a known sample all pointed the same way.
Claim only what the data show. His paper is a model of restraint.
For the structures behind isomerism, see our guide to stereoisomerism in organic chemistry, and for percentage composition, our post on common mole concept errors. When a composition or isomer question will not come out, the Fermi Problem Library has a step-by-step solver that explains the reasoning at each stage.
Try this now: ethanol and dimethyl ether are both C₂H₆O. Work out the percentage of oxygen in each, then name one test that would tell them apart.
