Phosphine

• Phosphine
• Phosphine
• Phosphine

Flammable, poisonous, colorless and odorless gas. Impurities smell of garlic and rotten fish

Gaseous

1.53 kg · m 3 (0 ° C)

-133.8 ° C

-87.77 ° C

3,49 MPa ( 20 ° C)

330 mg · l-1 (20 ° C ) in water

1.224 ( 16.85 ° C)

Risk

0.14 mg · m-3

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Monophosphane, colloquially somewhat imprecise as phosphine, phosphine or outdated called phosphine, belongs to the group of the phosphanes. Monophosphane is a chemical compound of the element phosphorus to the sum of the formula PH3. It is a flammable, highly toxic, odorless when pure gas. Pure monophosphane is self-igniting at 150 ° C only. However, due to the presence of diphosphine P2H4 commercially available and laboratory prepared gas burns even at room temperature in the presence of air; the diphosphine and other phosphines give this usually not quite pure monophosphane a strong odor of garlic.

Production and representation

There are numerous ways to display monophosphane. For example, disproportionation of white phosphorus (P4) in an alkaline medium to phosphine and phosphinic acid which is disproportionated at high temperatures to monophosphane and phosphonic acid, phosphoric acid, and which in turn is disproportionated to monophosphane:

This method is technically conducted in an autoclave at 250 ° C.

Analogously to the preparation of ammonia (Haber -Bosch process ) can also be a synthesis of the elements:

Monophosphane is also formed during the acid hydrolysis of the salt-like phosphides and phosphonium salts as well as the Hydridolyse from phosphorus halides such as phosphorus trichloride, lithium aluminum hydride in ether.

Properties

Physical Properties

Monophosphane is sparingly soluble in water, the aqueous solution is neutral.

The molecule is built trigonal pyramidal. The angle between the individual hydrogen atoms is 93.5 °. The distance between the phosphorus and the hydrogen atoms is 1.419 Å.

Chemical Properties

Monophosphane is a weak base ( pK ~ 27). With hydrogen halide acids it reacts to form unstable salts, the so-called phosphonium salts. At elevated temperature, it decomposes into the elements hydrogen and phosphorus.

With strong bases such as sodium hydride or butyllithium allows the hydrogen atoms replaced by alkali metals. By substitution of all hydrogen atoms, the so-called phosphides can be synthesized.

The standard reduction potential is in the acidic environment of -0.063 V, the basic -0.89 V.

At 150 ° C, pure monophosphane ignites in air and is oxidized to phosphoric acid:

In the presence of traces of diphosphine with 0.2 % to monophosphane immediately ignited spontaneously in the presence of air.

Use

Monophosphane is for pest control, used in particular for mice and insect control in grain silos and storage of plant products. The fumigation can be done by professionals directly with Monophosphangas. Instead, solid preparations are frequently (eg with the active ingredient aluminum phosphide AlP or calcium phosphide Ca3P2 ) designed to react with the humidity and so release the Monophosphangas.

It is also used in the manufacture of light-emitting diodes for the doping of silicon with phosphorus. It is also used for the synthesis of various organic compounds.

There have been hired even attempts to phosphorus fertilization by monophosphane.

Safety

Monophosphane is a very strong nerves and metabolic poison which is highly effective not only in mammals but also in insects even at low concentration. In humans, it raises blood pressure, vomiting, pulmonary edema and coma. In addition monophosphane is self-igniting by traces of diphosphine in the air, which makes handling very delicate.

Proof

Monophosphane is most easily demonstrated with so-called test tube or appropriate sensors. Moreover, the odor of phosphane (specifically, the odor of the impurities present ) from a concentration of 2 ppm perceptible.