ไฮดราซีน, Hydrazine, ไฮดราซีนไฮเดรต, Hydrazine Hydrate, N2H2

ไฮดราซีน, Hydrazine, ไฮดราซีนไฮเดรต, ไฮดราซีนไฮเดรท, Hydrazine Hydrate, N2H2

Hydrazine (also called diazane) is

an inorganic compound with the formula N2H4. It is a colourless flammable

liquid with an ammonia-like odor. Hydrazine is highly toxic and dangerously

unstable unless handled in solution. As of 2002, approximately 260,000 tons

were manufactured annually. Hydrazine is mainly used as a foaming agent in

preparing polymer foams, but significant applications also include its uses as

a precursor to polymerization catalysts and pharmaceuticals. Additionally,

hydrazine is used in various rocket fuels and to prepare the gas precursors

used in air bags. Hydrazine is used within both nuclear and conventional

electrical power plant steam cycles as an oxygen scavenger to control

concentrations of dissolved oxygen in an effort to reduce corrosion.

Applications

The majority use of hydrazine is

as a precursor to blowing agents. Specific compounds include azodicarbonamide

and azobisisobutyronitrile, which yield 100-200 mL of gas per gram of

precursor. In a related application, sodium azide, the gas-forming agent in air

bags, is produced from hydrazine by reaction with sodium nitrite.

Hydrazine is also used as a

propellant on board space vehicles, and to both reduce the concentration of

dissolved oxygen in and control pH of water used in large industrial boilers.

The F-16 fighter jet uses hydrazine to fuel the aircraft's emergency power unit.

Precursor to pesticides and

pharmaceuticals

Hydrazine is a useful building

block in organic synthesis of pharmaceuticals and pesticides. One example is

3-amino-1,2,4-triazole and another is maleic hydrazide. The antitubercular drug

isoniazid is prepared from hydrazine.

Hydrazine in biology

Hydrazine is the intermediate in

the anaerobic oxidation of ammonia (anammox) process. It is produced by some

yeasts and the open ocean bacterium anammox (Brocadia anammoxidans). The false

morel produces the poison gyromitrin which is an organic derivative of

hydrazine that is converted to monomethylhydrazine by metabolic processes. Even

the most popular edible "button" mushroom Agaricus bisporus produces

organic hydrazine derivatives, including agaritine, a hydrazine derivative of

an amino acid, and gyromitrin.

 Organic chemistry

Hydrazines are part of many

organic syntheses, often those of practical significance in pharmaceuticals,

such as the antituberculosis medication isoniazid and the antifungal

fluconazole, as well as in textile dyes and in photography.

Hydrazone formation

Illustrative of the condensation

of hydrazine with a simple carbonyl is its reaction with propanone to give the

diisopropylidene hydrazine (acetone azine). The latter reacts further with hydrazine

to yield the hydrazone:

 2 (CH3)2CO + N2H4 ? 2 H2O + [(CH3)2C=N]2 [(CH3)2C=N]2 + N2H4 ? 2 (CH3)2C=NNH2

The propanone azine is an

intermediate in the Atofina-PCUK synthesis. Direct alkylation of hydrazines

with alkyl halides in the presence of base yields alkyl-substituted hydrazines,

but the reaction is typically inefficient due to poor control on level of

substitution (same as in ordinary amines). The reduction of hydrazones to

hydrazines present a clean way to produce 1,1-dialkylated hydrazines.

In a related reaction,

2-cyanopyridines react with hydrazine to form amide hydrazides, which can be

converted using 1,2-diketones into triazines.

Wolff-Kishner reduction

Hydrazine is used in the

Wolff-Kishner reduction, a reaction that transforms the carbonyl group of a

ketone into a methylene bridge (or an aldehyde into a methyl group) via a

hydrazone intermediate. The production of the highly stable dinitrogen from the

hydrazine derivative helps to drive the reaction.

Heterocyclic chemistry

Being bifunctional, with two

amines, hydrazine is a key building block for the preparation of many

heterocyclic compounds via condensation with a range of difunctional

electrophiles. With 2,4-pentanedione, it condenses to give the

3,5-dimethylpyrazole. In the Einhorn-Brunner reaction hydrazines react with

imides to give triazoles.

Sulfonation

Being a good nucleophile, N2H4 can

attack sulfonyl halides and acyl halides. The tosylhydrazine also forms

hydrazones upon treatment with carbonyls.

Deprotection of phthalimides

Hydrazine is used to cleave

N-alkylated phthalimide derivatives. This scission reaction allows phthalimide

anion to be used as amine precursor in the Gabriel synthesis.

Reducing agent

Hydrazine is a convenient

reductant because the by-products are typically nitrogen gas and water. Thus,

it is used as an antioxidant, an oxygen scavenger, and a corrosion inhibitor in

water boilers and heating systems. It is also used to reduce metal salts and

oxides to the pure metals in electroless nickel plating and plutonium

extraction from nuclear reactor waste. Some colour photographic processes also

use a weak solution of hydrazine as a stabilizing wash, as it scavenges dye

coupler and unreacted silver halides. Hydrazine is the most common and

effective reducing agent used to convert graphene oxide (GO) to reduced

graphene oxide (rGO) via hydrothermal treatment.

Hydrazinium salts

Hydrazine is converted to solid

salts by treatment with mineral acids. A common salt is hydrazine sulfate,

[N2H5]HSO4, called hydrazinium sulfate. Hydrazine sulfate was investigated as a

treatment of cancer-induced cachexia, but proved ineffective.

Hydrazine azide (N5H5), the salt

of hydrazine and hydrazoic acid, was of scientific interest, because of its

high nitrogen content and explosive properties. Structurally,

with sulfuric acid gives

quantitative yields of pure hydrazine sulfate and hydrazoic acid.

Other industrial uses

Hydrazine is used in many

processes including: production of spandex fibers, as a polymerization catalyst;

in fuel cells, solder fluxes; and photographic developers, as a chain extender

in urethane polymerizations, and heat stabilizers. In addition, a semiconductor

deposition technique using hydrazine has recently been demonstrated, with

possible application to the manufacture of thin-film transistors used in liquid

crystal displays. Hydrazine in a 70% hydrazine, 30% water solution is used to

power the EPU (emergency power unit) on the Lockheed F-16 Fighting Falcon

fighter plane. The explosive Astrolite is made by combining hydrazine with

ammonium nitrate.

Hydrazine is often used as an

oxygen scavenger and corrosion inhibitor in boiler water treatment. However due

to the toxicity and certain undesired effects[clarification needed] this

practice is discouraged.[citation needed

Hydrazine was first used as a

rocket fuel during World War II for the Messerschmitt Me 163B (the first

rocket-powered fighter plane), under the code name B-Stoff (hydrazine hydrate).

When mixed with methanol (M-Stoff) and water it was called C-Stoff.[citation

needed]

Hydrazine is also used as a

low-power monopropellant for the maneuvering thrusters of spacecraft, and the

Space Shuttle's auxiliary power units (APUs). In addition, monopropellant

hydrazine-fueled rocket engines are often used in terminal descent of

spacecraft. Such engines were used on the Viking program landers in the 1970s

as well as the Phoenix lander and Curiosity rover which landed on Mars in May

2008 and August 2012, respectively.

In all hydrazine monopropellant

engines, the hydrazine is passed by a catalyst such as iridium metal supported

by high-surface-area alumina (aluminium oxide) or carbon nanofibers, or more

recently molybdenum nitride on alumina,[31] which causes it to decompose into

ammonia, nitrogen gas, and hydrogen gas according to the following

reactions:[citation needed]

 1.3 N2H4 ? 4 NH3 + N2

 2.N2H4 ? N2 + 2 H2

 3.4 NH3 + N2H4 ? 3 N2 + 8 H2

Reactions 1 and 2 are extremely

exothermic (the catalyst chamber can reach 800 ?C in a matter of milliseconds,)

and they produce large volumes of hot gas from a small volume of liquid, making

hydrazine a fairly efficient thruster propellant with a vacuum specific impulse

of about 220 seconds. Reaction 3 is endothermic and so reduces the temperature

of the products, but also produces a greater number of molecules. The catalyst

structure affects the proportion of the NH3 that is dissociated in Reaction 3;

a higher temperature is desirable for rocket thrusters, while more molecules

are desirable when the reactions are intended to produce greater quantities of

gas[citation needed].

Other variants of hydrazine that

are used as rocket fuel are monomethylhydrazine, (CH3)NH(NH2) (also known as

MMH), and unsymmetrical dimethylhydrazine, (CH3)2N(NH2) (also known as UDMH).

These derivatives are used in two-component rocket fuels, often together with

nitrogen tetroxide, N2O4, sometimes known as dinitrogen tetroxide. These

reactions are extremely exothermic, and the burning is also hypergolic, which

means that it starts without any external ignition source.

There are ongoing efforts to

replace hydrazine along with other highly toxic substances from the aerospace

industry. Promising alternatives include hydroxylammonium nitrate, 2-Dimethylaminoethylazide(DMAZ)and

energetic ionic liquids.

Fuel cells

The Italian catalyst manufacturer

Acta has proposed using hydrazine as an alternative to hydrogen in fuel cells.

The chief benefit of using hydrazine is that it can produce over 200 mW/cm2

more[clarification needed] than a similar hydrogen cell without the need to use

expensive platinum catalysts. As the fuel is liquid at room temperature, it can

be handled and stored more easily than hydrogen. By storing the hydrazine in a

tank full of a double-bonded carbon-oxygen carbonyl, the fuel reacts and forms

a safe solid called hydrazone. By then flushing the tank with warm water, the

liquid hydrazine hydrate is released. Hydrazine has a higher electromotive

force of 1.56 V compared to 1.23 V for hydrogen. Hydrazine breaks down in the

cell to form nitrogen and hydrogen which bonds with oxygen, releasing water.

Hydrazine was used in fuel cells manufactured by Allis-Chalmers Corp.,

including some that provided electric power in space satellites in the 1960s.

Gun propellant

A mixture of 63% hydrazine, 32%

hydrazine nitrate and 5% water is a standard propellant for experimental

bulk-loaded liquid propellant artillery. The propellant mixture above is

notable for being one of the most predictable and stable, with a remarkably

flat pressure profile during firing. Misfires are usually caused by inadequate

ignition. The movement of the shell after a misignition causes a large bubble

with a larger ignition surface area, and the greater rate of gas production

causes very high pressure, sometimes including catastrophic tube failures (i.e.

explosions).

Hydrazine hydrate is widely used

as a reducing agent or an intermediate of synthesis in various industrial

sectors like water treatment (effluents, industrial boilers), chemical

treatment process (metals, mine extraction) or active ingredients synthesis

(pharmaceuticals and agrochemicals).

Hydrazine hydrate is marketed as a

water-based solution at different hydrazine concentration

Hydrazine derivatives are used in the manufacture of herbicides and fungicides, as well as plant growth regulators. From tranquilizers to the primary drug for controlling tuberculosis, hydrazine derivatives have proven to be effective ingredients for a number of pharmaceuticals. Used as an oxygen scavenger in boiler water, 35% hydrazine solution reduces oxidation in both low and high pressure steam systems.

In fact,

hydrazine is the best material that can be used for protection against

oxidation in super critical boilers operating at pressures up to 3500 psi.

Currently,

the plastics industry uses hydrazine derivatives in the creation of blowing

agents and polymerization initiators. Use of these derivatives is also being

investigated for the formulation of polymers.

Terminology

Hydrazine solution strength is usually given as the percent

contained hydrazine. However, when hydrazine and water are mixed, a monohydrate

(N2H4.H20) is formed through hydrogen bonding. Therefore, the amount of

hydrazine in a solution can also be designated as the percentage of hydrazine

monohydrate. There is a simple relationship between the two designations, based

on their molecular weights.

Hydrazine has

a molecular weight of 32 and the monohydrate has a molecular weight of 50. The

ratio of their weight is 32/50 or 0.64. Therefore, 100% monohydrate would contain

32/50 or 64% hydrazine. This is the reason 100% hydrazine hydrate can be used

interchangeably with 64% contained hydrazine by weight.

To avoid

confusion caused by dual terminology, always expresses hydrazine content in

terms of contained hydrazine. Since other companies may not follow this

convention, users should ascertain which terminology applies when reference to

hydrazine solution concentration is involved.

Uses: This

product is widely used in the manufacture of pure metal, the thermal power

plant boiler antioxidant, synthetic fibers, dyes, imaging, restore, and other

chemicals, pigments, resin, food, defense industry, scientific research,

organic synthesis, pesticides and raw material of manufacturing intermediates

of AC foaming agent .

 

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