Preparation, properties, structure and uses of phosphine and phosphorus halides,(PCl3. PCl5)

Phosphine is a chemical that belongs to the group of organophosphorus compounds. This type of compound was first developed in the year 1783 by Philippe Gengembre. Dr Phillippe obtained the formula of phosphine by using heat to phosphorus in an aqueous solution Chemical formula of this compound is PH3.

What is phosphine?

As discussed earlier, it is a chemical compound of Phosphorus that belongs to the organophosphorus compounds. The formula of this compound is PH3. The concentration of this compound varies with the atmosphere and it also plays an important role in the phosphorus biogeochemical cycle.

Structure of Phosphine

 This compound is generally a trigonal pyramidal molecule. The length of the P-H Bond is about 1.42 angle while the H-P-H Bond is almost about 93.5 degrees.

Chemical preparation of this Phosphine compound:

When the compound of calcium phosphide is mixed with water or with HCL, the chemical properties of this compound will be:

Ca3P2 + 6H2O → 3Ca(OH)2 + 2PH3

Ca3P2 + 6HCl → 3CaCl2 + 2PH3

When the white phosphorus has been heated with the concentrated sodium hydroxide, CO2 from the atmosphere will mix in the inert solution, thus it will form Phosphine.

P4 + 3NaOH + 3H2O → PH3 + 3NaH2PO2

Physical and the chemical properties 

• It will look like a colourless gas smell like rotten fish.
• This gas is highly poisonous.
• PH3 can be considered as sparingly soluble in water and it is soluble in organic solvents. 
• PH3 will become a lewis base by donating a sible pair of electrons when it reacts with hydrogen iodide.
• In normal conditions, it will be a non-combustible gas. When it gains heat, it will catch fire easily and, as a result, it will form Phosphoric acid.

PH3+2O2→ H3PO4

• If this compound comes in contact with any type of oxidizing agent then it will explode soon.

How is phosphine purified?

Few techniques are there that help to purify phosphine. By dropping water on the calcium chloride phosphide. This compound can also be purified with the help of HI to get PH4I. that reacts with the KOH to form the pure PH3KI water.

Use of phosphine gas (PH3)

• It is mainly used in the semiconductor factory in a small amount as the dopant.
• Phosphine is also used in Holem’s signal due to the property that this compound contains spontaneous combustion.
• It is also used as a fumigant and works like a polymerization initiator.
• It also helps to create several flame retardants
• phosphine gas helps to develop garlic odour also.

Though required in almost every sector, phosphine is hard to maintain and is flammable also. 

What are phosphorus halides?

A phosphorus halide is a type of compound that helps to form phosphorus with the halogen. 

phosphorus halides are known due to the formation of two types of halides, PX3 and PX5. There are various types of phosphorus halides; the most common are phosphorus Pentachloride (PCl5) and phosphorus trichloride (PCl3).  Phosphorus trichloride is basically an oily liquid and highly toxic type of compound.

It could be anything from fluorine, chlorine, bromine, to iodine. As we discussed earlier, the most common phosphorus halide is chloride. These chlorides are usually covalent in nature.  Here we refer to X as Halogen. The chemical preparation of these atoms are as follows:

• When a dry type of chlorine has its heated effect on white phosphorus then phosphorus trichloride is formed.

  P4 + 6Cl2 → 4PCl3

• Whenever the thionyl chloride starts reacting with the white phosphorus, then phosphorus trichloride will produce.

P + 8SOCl2 → 4PCl3 + 4SO2 + 2S2Cl2

Phosphorus pentachloride is basically a yellowish-white water-sensitive solid. This compound is easily soluble with carbon tetrachloride and others like carbon disulfide, benzene and diethyl ether.  Its structure looks bipyramidal in gaseous state and in liquid phases. 

In solid state, it acts like an ionic solid [PCl4]+[PCl6]– in this chemical formula cation is positive and tetrahedral and the anion is negative particle  [PCl6]– is octahedral chemical preparation of this compound.

• When the white phosphorus comes with the effect of dry chlorine then it will produce  Phosphorus pentachloride. 

P4 + 10Cl2→4PCl5

This can also be prepared with the help of SO2Cl2 and phosphorus 

P4 + 10SO2Cl2→4PCl5+10SO2

Uses of phosphorus halides

There are various types of uses of this compound as follows:

• This compound is mainly used as the chlorinating agent. It helps to clean swimming pools by doing pool shock.
• This compound helps with water treatment agents. 
• It also works like organophosphorus pesticides 
• phosphorus halides are one of the most important items of lube oil.

Conclusion

Phosphine is one of the most important chapters that you will study in class XII Chemistry.  This compound has various advantages and it is mainly used in industries like the semiconductor industry.  This compound works there as a dopant that helps to improve the conductivity of semiconductors.  In this chapter, we provided some main points about phosphorus halides and the uses of this compound and the chemical properties.