Ammoxidation
Encyclopedia
In chemistry, ammoxidation is an industrial process for the production of nitrile
s using ammonia
and oxygen
. The usual substrates are alkene
s. It is sometimes called the Sohio process, acknowledging that ammoxidation was commercialized by Standard Oil of Ohio
. An important application of this process is the production of acrylonitrile
:
Several million tons of acrylonitrile are produced in this way annually. The world's supply of the solvent acetonitrile
is a byproduct of this particular process.
ic position of unsaturated hydrocarbons. Benzyl
ic C-H bonds are also susceptible to ammoxidation, reflecting the weakness of their C-H bonds. For this reason, cyanopyridines (e.g. the precursor to niacin
) and benzonitrile
s are produced from methylpyridine
s and toluene
, respectively. Dinitriles are produced by double ammoxidation, examples being phthalonitrile
s (precursor to phthalocyanine
s) and terephthalonitriles, both from xylene
s.
Typical catalysts are the oxides of vanadium and molybdenum. π-Allyl complexes are assumed as intermediates.
s and aldehyde
s are competent substrates:
These substrates are usually more expensive than the alkenes, so they are less common.
Hydrogen cyanide is prepared by an ammoxidation-like reaction of methane, the Andrussov oxidation:
Nitrile
A nitrile is any organic compound that has a -C≡N functional group. The prefix cyano- is used interchangeably with the term nitrile in industrial literature. Nitriles are found in many useful compounds, one example being super glue .Inorganic compounds containing the -C≡N group are not called...
s using ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
and oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
. The usual substrates are alkene
Alkene
In organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond...
s. It is sometimes called the Sohio process, acknowledging that ammoxidation was commercialized by Standard Oil of Ohio
Standard Oil of Ohio
Standard Oil of Ohio or Sohio was an American oil company that was acquired by British Petroleum, now called BP.It was one of the successor companies to Standard Oil after the antitrust breakup in 1911. Standard Oil of Ohio was the original Standard Oil company founded by John D. Rockefeller. It...
. An important application of this process is the production of acrylonitrile
Acrylonitrile
Acrylonitrile is the chemical compound with the formula C3H3N. This pungent-smelling colorless liquid often appears yellow due to impurities. It is an important monomer for the manufacture of useful plastics. In terms of its molecular structure, it consists of a vinyl group linked to a nitrile...
:
- CH3CH=CH2 + 3/2 O2 + NH3 → NCCH=CH2 + 3 H2O
Several million tons of acrylonitrile are produced in this way annually. The world's supply of the solvent acetonitrile
Acetonitrile
Acetonitrile is the chemical compound with formula . This colourless liquid is the simplest organic nitrile. It is produced mainly as a byproduct of acrylonitrile manufacture...
is a byproduct of this particular process.
Scope
Ammoxidation of alkenes exploits the weak C-H bonds that are located in the allylAllyl
An allyl group is a substituent with the structural formula H2C=CH-CH2R, where R is the connection to the rest of the molecule. It is made up of a methylene , attached to a vinyl group . The name is derived from the Latin word for garlic, Allium sativum. Theodor Wertheim isolated an allyl...
ic position of unsaturated hydrocarbons. Benzyl
Benzyl
In organic chemistry, benzyl is the term used to describe the substituent or molecular fragment possessing the structure C6H5CH2-. Benzyl features a benzene ring attached to a CH2 group.-Nomenclature:...
ic C-H bonds are also susceptible to ammoxidation, reflecting the weakness of their C-H bonds. For this reason, cyanopyridines (e.g. the precursor to niacin
Niacin
"Niacin" redirects here. For the neo-fusion band, see Niacin .Niacin is an organic compound with the formula and, depending on the definition used, one of the forty to eighty essential human nutrients.Niacin is one of five vitamins associated with a pandemic deficiency disease: niacin deficiency...
) and benzonitrile
Benzonitrile
Benzonitrile is the chemical compound with the formula C6H5CN, abbreviated PhCN. This aromatic organic compound is colourless, with a sweet almond odour. It is prepared by the dehydration of benzamide, or by the reaction of sodium cyanide with bromobenzene....
s are produced from methylpyridine
Pyridine
Pyridine is a basic heterocyclic organic compound with the chemical formula C5H5N. It is structurally related to benzene, with one C-H group replaced by a nitrogen atom...
s and toluene
Toluene
Toluene, formerly known as toluol, is a clear, water-insoluble liquid with the typical smell of paint thinners. It is a mono-substituted benzene derivative, i.e., one in which a single hydrogen atom from the benzene molecule has been replaced by a univalent group, in this case CH3.It is an aromatic...
, respectively. Dinitriles are produced by double ammoxidation, examples being phthalonitrile
Phthalonitrile
Phthalonitrile is an organic compound with the formula C6H42, which is an off-white crystal solid at room temperature. It is a benzene derivative, containing two adjacent nitrile groups. The compound is partially soluble in water, and is soluble in acetone, nitrobenzene, and benzonitrile...
s (precursor to phthalocyanine
Phthalocyanine
Phthalocyanine is an intensely blue-green coloured macrocyclic compound that is widely used in dyeing. Phthalocyanines form coordination complexes with most elements of the periodic table...
s) and terephthalonitriles, both from xylene
Xylene
Xylene encompasses three isomers of dimethylbenzene. The isomers are distinguished by the designations ortho- , meta- , and para- , which specify to which carbon atoms the two methyl groups are attached...
s.
Typical catalysts are the oxides of vanadium and molybdenum. π-Allyl complexes are assumed as intermediates.
Related processes
Instead of alkenes, alcoholAlcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
s and aldehyde
Aldehyde
An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....
s are competent substrates:
- O=CHCH=CH2 + 1/2 O2 + NH3 → NCCH=CH2 + 2 H2O
- HOCH2CH=CH2 + O2 + NH3 → NCCH=CH2 + 3 H2O
These substrates are usually more expensive than the alkenes, so they are less common.
Hydrogen cyanide is prepared by an ammoxidation-like reaction of methane, the Andrussov oxidation:
- CH4 + NH3 + 3/2 O2 → HCN + 3 H2O