Hydrazines (R₂N−NR₂) are a class of chemical compounds with two

nitrogen atom Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at seven ...

s 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 Hydrazine is an inorganic compound with the chemical formula . It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly toxic unless handled in solution as, for example, hydrazine ...

(H₂N−NH₂), in which one or more hydrogen atoms have been replaced by hydrocarbon groups.

Production

* 1,1-Dimethylhydrazine is produced by the reduction of ''N''-nitrosodimethylamine. Siegfried Hauptmann: ''Organische Chemie'', 2. durchgesehene Auflage, VEB Deutscher Verlag für Grundstoffindustrie, Leipzig, 1985, S. 522–523, . * The reduction of

benzenediazonium chloride Benzenediazonium tetrafluoroborate is an organic compound with the formula 6H5N2F4. It is a salt of a diazonium cation and tetrafluoroborate. It exists as a colourless solid that is soluble in polar solvents. It is the parent member of the ary ...

with

tin(II) chloride Tin(II) chloride, also known as stannous chloride, is a white crystalline solid with the formula . It forms a stable dihydrate, but aqueous solutions tend to undergo hydrolysis, particularly if hot. SnCl2 is widely used as a reducing agent (in aci ...

and hydrochloric acid provides

phenylhydrazine Phenylhydrazine is the chemical compound with the formula . It is often abbreviated as . It is also found in edible mushrooms. Properties Phenylhydrazine forms monoclinic prisms that melt to an oil around room temperature which may turn yellow ...

. * 2,4-Dinitrophenylhydrazine is produced by the reaction of 1-chloro-2,4-dinitrobenzene with hydrazine. * Tetraphenylhydrazine is formed by the oxidation of diphenylamine with

potassium permanganate Potassium permanganate is an inorganic compound with the chemical formula KMnO4. It is a purplish-black crystalline salt, that dissolves in water as K+ and , an intensely pink to purple solution. Potassium permanganate is widely used in the c ...

in acetone.

Classification

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.{{Citation, last=Schirmann, first=Jean-Pierre, title=Hydrazine, date=2001-06-15, encyclopedia=Ullmann's Encyclopedia of Industrial Chemistry, editor-last=Wiley-VCH Verlag GmbH & Co. KGaA, publisher=Wiley-VCH Verlag GmbH & Co. KGaA, language=en, doi=10.1002/14356007.a13_177, isbn=9783527306732, last2=Bourdauducq, first2=Paul 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 a violet or dark blue compounds.

History

Phenylhydrazine Phenylhydrazine is the chemical compound with the formula . It is often abbreviated as . It is also found in edible mushrooms. Properties Phenylhydrazine forms monoclinic prisms that melt to an oil around room temperature which may turn yellow ...

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

carbohydrate In organic chemistry, a carbohydrate () is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula (where ''m'' may or ma ...

s, because the reaction of the sugar's

aldehyde group In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl group ...

s lead to well crystallizing

phenylhydrazone Hydrazones are a class of organic compounds with the structure . They are related to ketones and aldehydes by the replacement of the oxygen =O with the = functional group. They are formed usually by the action of hydrazine on ketones or aldehydes. ...

s or

osazone Osazones are a class of carbohydrate derivatives found in organic chemistry formed when reducing sugars are reacted with excess of phenylhydrazine at boiling temperatures. Formation Osazone formation was developed by Emil Fischer, who used th ...

Examples

Organohydrazines and their derivatives are numerous, especially when

hydrazone Hydrazones are a class of organic compounds with the structure . They are related to ketones and aldehydes by the replacement of the oxygen =O with the = functional group. They are formed usually by the action of hydrazine on ketones or aldehyde ...

s are included. *

monomethyl hydrazine Monomethylhydrazine (mono-methyl hydrazine, MMH) is a highly toxic, volatile hydrazine derivative with the chemical formula . It is used as a rocket propellant in bipropellant rocket engines because it is hypergolic with various oxidizers such as ...

, where one of the hydrogen atoms on the hydrazine molecule has been replaced with a methyl group (CH₃). 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 symmetrical dimethylhydrazine, or 1,2-Dimethylhydrazine, is the organic compound with the formula (CH3NH)2. It is one of the two isomers of dimethylhydrazine. Both isomers are colorless liquids at room temperature, with properties similar to thos ...

) are hydrazines where two hydrogen atoms are replaced by

methyl group In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula . In formulas, the group is often abbreviated as Me. This hydrocarbon group occurs in many ...

s. UDMH is the easier of the two to manufacture and is a fairly common rocket fuel. * gyromitrin and

agaritine Agaritine is an aromatic hydrazine-derivative mycotoxin in mushroom species of the genus ''Agaricus''. It is an α-aminoacid and a derivative of phenylhydrazine. Occurrence Agaritine is present as a natural phytochemical in fresh samples of at ...

are hydrazine derivatives found in the commercially produced mushroom species ''

Agaricus bisporus ''Agaricus bisporus'' is an edible basidiomycete mushroom native to grasslands in Eurasia and North America. It has two color states while immature – white and brown – both of which have various names, with additional names for the mature ...

''. Gyromitrin is metabolized into monomethyl hydrazine. *

Isoniazid Isoniazid, also known as isonicotinic acid hydrazide (INH), is an antibiotic used for the treatment of tuberculosis. For active tuberculosis it is often used together with rifampicin, pyrazinamide, and either streptomycin or ethambutol. For la ...

iproniazid Iproniazid (Marsilid, Rivivol, Euphozid, Iprazid, Ipronid, Ipronin) is a non-selective, irreversible monoamine oxidase inhibitor (MAOI) of the hydrazine class. It is a xenobiotic that was originally designed to treat tuberculosis, but was lat ...

hydralazine Hydralazine, sold under the brand name Apresoline among others, is a medication used to treat high blood pressure and heart failure. This includes high blood pressure in pregnancy and very high blood pressure resulting in symptoms. It has been ...

, and

phenelzine Phenelzine, sold under the brand name Nardil, among others, is a non-selective and irreversible monoamine oxidase inhibitor (MAOI) of the hydrazine class which is primarily used as an antidepressant and anxiolytic. Along with tranylcypromine and ...

are

medication A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to diagnose, cure, treat, or prevent disease. Drug therapy (pharmacotherapy) is an important part of the medical field and re ...

s whose molecules contain hydrazine-like structures. * 2,4-dinitrophenylhydrazine (2,4-DNPH) is commonly used to test for

ketones In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bon ...

and

aldehydes In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl grou ...

in organic and

clinical chemistry Clinical chemistry (also known as chemical pathology, clinical biochemistry or medical biochemistry) is the area of chemistry that is generally concerned with analysis of bodily fluids for diagnostic and therapeutic purposes. It is an applied ...

. *

, C₆H₅NHNH₂, the first hydrazine to be discovered.

References

Functional groups Organonitrogen compounds