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Class of chemical compounds
Hydrazines
(R
2
N?NR
2
) are a class of chemical compounds with two
nitrogen atoms
linked via a covalent bond and which carry from one up to four alkyl or aryl substituents. Hydrazines can be considered as derivatives of the inorganic
hydrazine
(H
2
N?NH
2
), in which one or more hydrogen atoms have been replaced by hydrocarbon groups.
[1]
Production
[
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]
Classification
[
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]
Hydrazines can be divided into three groups according to the degree of substitution. Hydrazines belonging to the same group behave similarly in their chemical properties. Monosubstituted hydrazines and so-called asymmetrically disubstituted hydrazines, where (only) two hydrocarbon groups are bonded to the same nitrogen atom are colorless liquids. Aliphatic monosubstituted and asymmetrically disubstituted hydrazines are very water soluble, strongly alkaline and good reducing agents. Aromatic monosubstituted and asymmetrically disubstituted hydrazines are poorly soluble in water, less basic and weaker reducing agents. For the preparation of aliphatic hydrazines, the reaction of hydrazine with alkylating compounds such as alkyl halides is used, or by reduction of nitroso derivatives. Aromatic hydrazines are prepared by reducing aromatic diazonium salts.
[3]
[4]
In symmetric disubstituted hydrazines, a hydrocarbon group is bonded to each of the hydrazine nitrogen atoms. Like asymmetrically disubstituted hydrazines, they are liquids, but their boiling points are typically higher. In particular, the aliphatic compounds are basic and reducing agents and are soluble in water. Aromatic symmetric disubstituted hydrazines are not soluble in water. Symmetrically disubstituted hydrazines are prepared by reducing nitro compounds under basic conditions or by reducing the azines.
Tri- or tetrasubstituted aliphatic hydrazines are water-insoluble weakly basic compounds. The corresponding arylhydrazines are solid colorless substances which are insoluble in water and substantially not basic. They react with concentrated
sulfuric acid
to form violet or dark blue compounds.
History
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Phenylhydrazine
and
2,4-dinitrophenylhydrazine
have were used historically in analytical chemistry to detect and identify compounds with carbonyl groups. Phenylhydrazine was used to study the structure of
carbohydrates
, because the reaction of the sugar's
aldehyde groups
lead to well crystallizing
phenylhydrazones
or
osazones
.
Examples
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]
Organohydrazines and their derivatives are numerous, especially when
hydrazones
are included.
- monomethyl hydrazine
, where one of the hydrogen atoms on the hydrazine molecule has been replaced with a methyl group (CH
3
). Due to the symmetry of the hydrazine molecule, it does not matter which hydrogen atom is replaced. It is sometimes used as a rocket fuel.
- 1,1-dimethylhydrazine
(unsymmetrical dimethylhydrazine, UDMH) and
1,2-dimethylhydrazine
(
symmetrical dimethylhydrazine
) are hydrazines where two hydrogen atoms are replaced by
methyl groups
. UDMH is the easier of the two to manufacture and is a fairly common rocket fuel.
- gyromitrin
and
agaritine
are hydrazine derivatives found in the commercially produced mushroom species
Agaricus bisporus
.
Gyromitrin
is metabolized into monomethyl hydrazine.
- Isoniazid
,
iproniazid
,
hydralazine
, and
phenelzine
are
medications
whose molecules contain hydrazine-like structures.
- 2,4-dinitrophenylhydrazine
(2,4-DNPH) is commonly used to test for
ketones
and
aldehydes
in
organic
and
clinical chemistry
.
- phenylhydrazine
, C
6
H
5
NHNH
2
, the first hydrazine to be discovered.
References
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]
- ^
Ni?, Miloslav; Jirat, Ji?i; Ko?ata, Bed?ich; Jenkins, Aubrey; McNaught, Alan, eds. (2009-06-12).
IUPAC Compendium of Chemical Terminology: Gold Book
(2.1.0 ed.). Research Triangle Park, NC: IUPAC.
doi
:
10.1351/goldbook
.
ISBN
9780967855097
.
- ^
a
b
c
d
Siegfried Hauptmann
:
Organische Chemie
, 2. durchgesehene Auflage, VEB Deutscher Verlag fur Grundstoffindustrie, Leipzig, 1985, S. 522?523,
ISBN
3-342-00280-8
.
- ^
Rothgery, Eugene F. (2004-11-19), "Hydrazine and Its Derivatives", in John Wiley & Sons, Inc. (ed.),
Kirk-Othmer Encyclopedia of Chemical Technology
, John Wiley & Sons, Inc.,
doi
:
10.1002/0471238961.0825041819030809.a01.pub2
,
ISBN
9780471238966
- ^
Schirmann, Jean-Pierre; Bourdauducq, Paul (2001-06-15), "Hydrazine", in Wiley-VCH Verlag GmbH & Co. KGaA (ed.),
Ullmann's Encyclopedia of Industrial Chemistry
, Wiley-VCH Verlag GmbH & Co. KGaA,
doi
:
10.1002/14356007.a13_177
,
ISBN
9783527306732