The Wöhler synthesis is the conversion of

ammonium cyanate Ammonium cyanate is an inorganic compound with the formula . It is a colorless, solid salt. Structure and reactions The structure of this salt was verified by X-ray crystallography. The respective C–O and C–N distances are 1.174(8) and 1.1 ...

into

urea Urea, also known as carbamide, is an organic compound with chemical formula . This amide has two amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest amide of carbamic acid. Urea serves an important r ...

. This

chemical reaction A chemical reaction is a process that leads to the IUPAC nomenclature for organic transformations, chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the pos ...

was described in 1828 by

Friedrich Wöhler Friedrich Wöhler () FRS(For) HonFRSE (31 July 180023 September 1882) was a German chemist known for his work in inorganic chemistry, being the first to isolate the chemical elements beryllium and yttrium in pure metallic form. He was the firs ...

. It is often cited as the starting point of modern

organic chemistry Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clayden, J.; ...

. Although the Wöhler reaction concerns the conversion of ammonium cyanate, this

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantitie ...

appears only as an (unstable) intermediate. Wöhler demonstrated the reaction in his original publication with different sets of reactants: a combination of

cyanic acid Isocyanic acid is a chemical compound with the structural formula HNCO, which is often written as . It is a colourless, volatile and poisonous substance, with a boiling point of 23.5 °C. It is the predominant tautomer of cyanic acid (). ...

and

ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous was ...

, a combination of

silver cyanate Silver cyanate is the cyanate salt of silver Silver is a chemical element with the symbol Ag (from the Latin ', derived from the Proto-Indo-European ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, white, lustrous transit ...

and ammonium chloride, a combination of lead cyanate and ammonia and finally from a combination of mercury cyanate and cyanatic ammonia (which is again cyanic acid with ammonia).

Modified versions of the Wöhler synthesis

The reaction can be demonstrated by starting with

solution Solution may refer to: * Solution (chemistry), a mixture where one substance is dissolved in another * Solution (equation), in mathematics ** Numerical solution, in numerical analysis, approximate solutions within specified error bounds * Soluti ...

s of

potassium cyanate Potassium cyanate is an inorganic compound with the formula KOCN (sometimes denoted KCNO). It is a colourless solid. It is used to prepare many other compounds including useful herbicide. Worldwide production of the potassium and sodium salts was ...

and ammonium chloride which are mixed, heated and cooled again. An additional proof of the chemical transformation is obtained by adding a solution of

oxalic acid Oxalic acid is an organic acid with the systematic name ethanedioic acid and formula . It is the simplest dicarboxylic acid. It is a white crystalline solid that forms a colorless solution in water. Its name comes from the fact that early inve ...

which forms

oxalate Oxalate (IUPAC: ethanedioate) is an anion with the formula C2O42−. This dianion is colorless. It occurs naturally, including in some foods. It forms a variety of salts, for example sodium oxalate (Na2C2O4), and several esters such as dimethyl o ...

as a white

precipitate In an aqueous solution, precipitation is the process of transforming a dissolved substance into an insoluble solid from a super-saturated solution. The solid formed is called the precipitate. In case of an inorganic chemical reaction leading ...

. Alternatively the reaction can be carried out with lead cyanate and ammonia. The actual reaction taking place is a

double displacement reaction A salt metathesis reaction, sometimes called a double displacement reaction, is a chemical process involving the exchange of bonds between two reacting chemical species which results in the creation of products with similar or identical bonding a ...

to form ammonium cyanate: : + + 2H2O -> + Ammonium cyanate decomposes to

and

which in turn react to produce urea: : -> + HOCN <=> Complexation with

drives this

chemical equilibrium In a chemical reaction, chemical equilibrium is the state in which both the reactants and products are present in concentrations which have no further tendency to change with time, so that there is no observable change in the properties of the sy ...

to completion.

Debate

It is disputed that Wöhler's synthesis sparked the downfall of the theory of

vitalism Vitalism is a belief that starts from the premise that "living organisms are fundamentally different from non-living entities because they contain some non-physical element or are governed by different principles than are inanimate things." Wher ...

, which states that organic matter possessed a certain ''vital force'' common to all living things. Prior to the Wöhler synthesis, the work of

John Dalton John Dalton (; 5 or 6 September 1766 – 27 July 1844) was an English chemist, physicist and meteorologist. He is best known for introducing the atomic theory into chemistry, and for his research into colour blindness, which he had. Colour b ...

and

Jöns Jacob Berzelius Baron Jöns Jacob Berzelius (; by himself and his contemporaries named only Jacob Berzelius, 20 August 1779 – 7 August 1848) was a Swedish chemist. Berzelius is considered, along with Robert Boyle, John Dalton, and Antoine Lavoisier, to be on ...

had already convinced chemists that organic and inorganic matter obey the same chemical laws. It took until 1845 when Kolbe reported another inorganic – organic conversion (of

carbon disulfide Carbon disulfide (also spelled as carbon disulphide) is a neurotoxic, colorless, volatile liquid with the formula and structure . The compound is used frequently as a building block in organic chemistry as well as an industrial and chemical non ...

acetic acid Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main component ...

) before vitalism started to lose support. A 2000 survey found that 90% of chemical textbooks repeat some version of the Wöhler myth.

References

{{DEFAULTSORT:Wohler Synthesis Name reactions Organic reactions