Fischer-Hepp rearrangement
Encyclopedia
The Fischer-Hepp rearrangement is a rearrangement reaction
in which an aromatic N-nitroso or nitrosamine
converts to a carbon nitroso
compound:
This organic reaction
was first described by the German chemist Otto Philipp Fischer and
Eduard Hepp (June 11, 1851-June 18, 1917) in 1886, and is of importance because para-NO
secondary aniline
s cannot be prepared in a direct reaction.
The rearrangement reaction
takes place by reacting the nitrosamine
precursor with hydrochloric acid
. The chemical yield is generally good under these conditions, but often much poorer if a different acid
is used. The exact reaction mechanism
is unknown but there is evidence suggesting an intramolecular
reaction.
Rearrangement reaction
A rearrangement reaction is a broad class of organic reactions where the carbon skeleton of a molecule is rearranged to give a structural isomer of the original molecule. Often a substituent moves from one atom to another atom in the same molecule...
in which an aromatic N-nitroso or nitrosamine
Nitrosamine
Nitrosamines are chemical compounds of the chemical structure R1N-N=O, some of which are carcinogenic.-Usages:Nitrosamines are used in manufacture of some cosmetics, pesticides, and in most rubber products. -Occurrences:...
converts to a carbon nitroso
Nitroso
Nitroso refers to a functional group in organic chemistry which has the general formula RNO. Nitroso compounds are a class of organic compounds containing the nitroso functional group, R−N=O....
compound:
This organic reaction
Organic reaction
Organic reactions are chemical reactions involving organic compounds. The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions, photochemical reactions and redox reactions. In organic synthesis,...
was first described by the German chemist Otto Philipp Fischer and
Eduard Hepp (June 11, 1851-June 18, 1917) in 1886, and is of importance because para-NO
Nitroso
Nitroso refers to a functional group in organic chemistry which has the general formula RNO. Nitroso compounds are a class of organic compounds containing the nitroso functional group, R−N=O....
secondary aniline
Aniline
Aniline, phenylamine or aminobenzene is an organic compound with the formula C6H5NH2. Consisting of a phenyl group attached to an amino group, aniline is the prototypical aromatic amine. Being a precursor to many industrial chemicals, its main use is in the manufacture of precursors to polyurethane...
s cannot be prepared in a direct reaction.
The rearrangement reaction
Rearrangement reaction
A rearrangement reaction is a broad class of organic reactions where the carbon skeleton of a molecule is rearranged to give a structural isomer of the original molecule. Often a substituent moves from one atom to another atom in the same molecule...
takes place by reacting the nitrosamine
Nitrosamine
Nitrosamines are chemical compounds of the chemical structure R1N-N=O, some of which are carcinogenic.-Usages:Nitrosamines are used in manufacture of some cosmetics, pesticides, and in most rubber products. -Occurrences:...
precursor with hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
. The chemical yield is generally good under these conditions, but often much poorer if a different acid
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...
is used. The exact reaction mechanism
Reaction mechanism
In chemistry, a reaction mechanism is the step by step sequence of elementary reactions by which overall chemical change occurs.Although only the net chemical change is directly observable for most chemical reactions, experiments can often be designed that suggest the possible sequence of steps in...
is unknown but there is evidence suggesting an intramolecular
Intramolecular
Intramolecular in chemistry describes a process or characteristic limited within the structure of a single molecule, a property or phenomenon limited to the extent of a single molecule.- Examples :...
reaction.