Acetone cyanohydrin (ACH) is an

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon- hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. Th ...

used in the production of

methyl methacrylate Methyl methacrylate (MMA) is an organic compound with the formula CH2=C(CH3)COOCH3. This colorless liquid, the methyl ester of methacrylic acid (MAA), is a monomer produced on a large scale for the production of poly(methyl methacrylate) (PMMA) ...

, the

monomer In chemistry, a monomer ( ; ''mono-'', "one" + '' -mer'', "part") is a molecule that can react together with other monomer molecules to form a larger polymer chain or three-dimensional network in a process called polymerization. Classification ...

of the transparent plastic

polymethyl methacrylate Poly(methyl methacrylate) (PMMA) belongs to a group of materials called engineering plastics. It is a transparent thermoplastic. PMMA is also known as acrylic, acrylic glass, as well as by the trade names and brands Crylux, Plexiglas, Acrylit ...

(PMMA), also known as acrylic. It liberates

hydrogen cyanide Hydrogen cyanide, sometimes called prussic acid, is a chemical compound with the formula HCN and structure . It is a colorless, extremely poisonous, and flammable liquid that boils slightly above room temperature, at . HCN is produced on a ...

easily, so it is used as a source of such. For this reason, this cyanohydrin is also highly toxic.

Preparation

In the laboratory, this compound may be prepared by treating

sodium cyanide Sodium cyanide is a poisonous compound with the formula Na C N. It is a white, water-soluble solid. Cyanide has a high affinity for metals, which leads to the high toxicity of this salt. Its main application, in gold mining, also exploits its h ...

with

acetone Acetone (2-propanone or dimethyl ketone), is an organic compound with the formula . It is the simplest and smallest ketone (). It is a colorless, highly volatile and flammable liquid with a characteristic pungent odour. Acetone is miscible wi ...

, followed by acidification: : Synthesis of acetone cyanohydrin

Considering the high toxicity of acetone cyanohydrin, a lab scale production has been developed using a

microreactor A microreactor or microstructured reactor or microchannel reactor is a device in which chemical reactions take place in a confinement with typical lateral dimensions below 1 mm; the most typical form of such confinement are microchannels.''R ...

-scale

flow chemistry In flow chemistry, a chemical reaction is run in a continuously flowing stream rather than in batch production. In other words, pumps move fluid into a reactor, and where tubes join one another, the fluids contact one another. If these fluids ar ...

to avoid needing to manufacture and store large quantities of the reagent. Alternatively, a simplified procedure involves the action of sodium or potassium cyanide on the sodium

bisulfite adduct The bisulfite ion (IUPAC-recommended nomenclature: hydrogensulfite) is the ion . Salts containing the ion are also known as "sulfite lyes". Sodium bisulfite is used interchangeably with sodium metabisulfite (Na2S2O5). Sodium metabisulfite disso ...

of acetone prepared ''in situ''. This gives a less pure product, one that is nonetheless suitable for most syntheses.

Reactions

Acetone cyanohydrin is an intermediate en route to

. Treatment with sulfuric acid gives the sulfate ester of the

methacrylamide Methacrylamide is the organic compound with the formula CH2=C(CH3)C(O)NH2. A colorless or white solid, it is a monomer for the production of polymers and copolymers, some of which are used in hydrogels. Methacrylamide is also a precursor of meth ...

methanolysis In organic chemistry, transesterification is the process of exchanging the organic group R″ of an ester with the organic group R' of an alcohol. These reactions are often catalyzed by the addition of an acid or base catalyst. The reaction ca ...

of which gives

ammonium bisulfate Ammonium bisulfate, also known as ammonium hydrogen sulfate, is a white, crystalline solid with the formula (NH4)HSO4. This salt is the product of the half-neutralization of sulfuric acid by ammonia. Production It is commonly collected as a bypr ...

and methyl methacrylate. It is used as a surrogate in place of HCN, as illustrated by its use as a precursor to

lithium cyanide Lithium cyanide is an inorganic compound with the chemical formula LiCN. It is a toxic, white colored, hygroscopic, water-soluble salt that finds only niche uses. Preparation LiCN arises from the interaction of lithium hydroxide and hydrogen cya ...

: :(CH₃)₂C(OH)CN + LiH → (CH₃)₂CO + LiCN + H₂ In transhydrocyanation, an

equivalent Equivalence or Equivalent may refer to: Arts and entertainment *Album-equivalent unit, a measurement unit in the music industry *Equivalence class (music) *''Equivalent VIII'', or ''The Bricks'', a minimalist sculpture by Carl Andre *''Equivale ...

of HCN is transferred from acetone cyanohydrin to another acceptor, with acetone as byproduct. The transfer is an equilibrium process, initiated by base. The reaction can be driven by trapping reactions or by the use of a superior HCN acceptor, such as an aldehyde. In the

hydrocyanation In organic chemistry, hydrocyanation is a process for conversion of alkenes to nitriles. The reaction involves the addition of hydrogen cyanide and requires a catalyst. This conversion is conducted on an industrial scale for the production of pr ...

reaction of

butadiene 1,3-Butadiene () is the organic compound with the formula (CH2=CH)2. It is a colorless gas that is easily condensed to a liquid. It is important industrially as a precursor to synthetic rubber. The molecule can be viewed as the union of two vin ...

, the transfer is irreversible.

Natural occurrence

Cassava ''Manihot esculenta'', commonly called cassava (), manioc, or yuca (among numerous regional names), is a woody shrub of the spurge family, Euphorbiaceae, native to South America. Although a perennial plant, cassava is extensively cultivated a ...

tubers contain

linamarin Linamarin is a cyanogenic glucoside found in the leaves and roots of plants such as cassava, lima beans, and flax. It is a glucoside of acetone cyanohydrin. Upon exposure to enzymes and gut flora in the human intestine, linamarin and its methyla ...

, a glucoside of acetohydrin, and the enzyme

linamarase Linamarase, or beta-D-glucosidase (), is an enzyme found in many plants including cassava and the butter bean. In cassava it is found in the cell walls. When the plant is chewed or ground, it exposes the enzyme to compounds like linamarin and l ...

for hydrolysing the glucoside. Crushing the tubers releases these compounds and produces acetone cyanohydrin.

Safety

Acetone cyanohydrin is classified as an extremely hazardous substance in the US

Emergency Planning and Community Right-to-Know Act The Emergency Planning and Community Right-to-Know Act of 1986 is a United States federal law passed by the 99th United States Congress located at Title 42, Chapter 116 of the U.S. Code, concerned with emergency response preparedness. On Octo ...

and carries an

RCRA The Resource Conservation and Recovery Act (RCRA), enacted in 1976, is the principal federal law in the United States governing the disposal of solid waste and hazardous waste.United States. Resource Conservation and Recovery Act. , , ''et seq. ...

P069 waste code. The principal hazards of acetone cyanohydrin arise from its ready decomposition on contact with water, which releases highly toxic

References

External links

*{{SIDS, name=Acetone cyanohydrin, id=75865
CDC - NIOSH Pocket Guide to Chemical Hazards - Acetone Cyanohydrin
Cyanohydrins