Nitrosation is a process of converting organic compounds into
nitroso derivatives, i.e. compounds containing the R-NO functionality.
''C''-Nitroso compounds
''C''-Nitroso compounds, such as
nitrosobenzene, are typically prepared by
oxidation
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a ...
of
hydroxylamines
Hydroxylamine is an inorganic compound with the formula . The material is a white crystalline, hygroscopic compound.Greenwood and Earnshaw. ''Chemistry of the Elements.'' 2nd Edition. Reed Educational and Professional Publishing Ltd. pp. 431–43 ...
:
:RNHOH +
→ RNO + H
2O
''S''-Nitroso compounds
''S''-Nitroso compounds (
''S''-nitrosothiols) are typically prepared by
condensation
Condensation is the change of the state of matter from the gas phase into the liquid phase, and is the reverse of vaporization. The word most often refers to the water cycle. It can also be defined as the change in the state of water vapor ...
of a
thiol
In organic chemistry, a thiol (; ), or thiol derivative, is any organosulfur compound of the form , where R represents an alkyl or other organic substituent. The functional group itself is referred to as either a thiol group or a sulfhydryl gro ...
and
nitrous acid:
:RSH + HONO → RSNO + H
2O
''O''-Nitroso compounds
''O''-
Nitroso compounds are similar to ''S''-nitroso compounds, but are less reactive because the oxygen atom is less
nucleophilic
In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they a ...
than the sulfur atom. The formation of an alkyl nitrite from an alcohol and nitrous acid is a common example:
:ROH + HONO → RONO + H
2O
''N''-Nitrosamines
''N''-
Nitrosamine
In organic chemistry, nitrosamines (or more formally ''N''-Nitrosamines) are organic compounds with the chemical structure , where R is usually an alkyl group. They feature a nitroso group () bonded to a deprotonated amine. Most nitrosamines a ...
s, including the carcinogenic variety, arise from the reaction of
nitrite
The nitrite ion has the chemical formula . Nitrite (mostly sodium nitrite) is widely used throughout chemical and pharmaceutical industries. The nitrite anion is a pervasive intermediate in the nitrogen cycle in nature. The name nitrite also re ...
sources with
amino compounds, which can happen during the
curing of meat. Typically this reaction proceeds via the attack of the
nitrosonium electrophile on an amine:
:NO
2− + 2 H
+ → NO
+ + H
2O
:R
2NH + NO
+ → R
2N-NO + H
+
Formation of an ''N''-nitrosamine:
:The nitrosamine can then lose water through protonation to form
diazonium cation
Diazonium compounds or diazonium salts are a group of organic compounds sharing a common functional group where R can be any organic group, such as an alkyl or an aryl, and X is an inorganic or organic anion, such as a halide.
General properti ...
, which is a very useful intermediate to form different compounds.
References
External links
Nitrosation of Amines
{{Nitric oxide signaling
Organic reactions