 |
| Phosphorus Pentachloride |
Phosphorus pentachloride, commonly abbreviated as PCl5, is an important industrial chemical compound that is vital for many industrial applications and manufacturing processes. Some of its key uses and properties are discussed below.
Chemical Structure and Properties
PCl5 is a colorless solid that sublimes readily at room temperature. Its
molecular formula is PCl5 which means it consists of one phosphorus atom bonded
to five chlorine atoms. It forms orthorhombic crystals and has a melting point
of 107°C. PCl5 is highly reactive and easily hydrolyzes in the presence of water
to form phosphorous acid and hydrogen chloride. It also readily reacts with
alcohols, amines, and other derivatives of hydrogen halides. Due to its
reactivity, PCl5 must be stored and handled carefully.
Production of PCl5
Industrially, PCl5 is produced through the chlorination of elemental Phosphorus
Pentachloride. In this process, yellow phosphorus is heated with
chlorine gas at around 200-300°C in a vessel. The reaction takes place in vapor
phase according to the following chemical equation:
P4 + 5Cl2 → 4PCl5
This vapor-phase process allows for high conversion rates of around 95%. The
crude PCl5 obtained is purified through distillation to obtain colorless and
pure liquid PCl5. The production capacity of PCl5 in major like the USA, Europe
and Asia is several hundred thousand tons annually.
Uses of Phosphorus Pentachloride
Due to its high reactivity as a chlorinating and dehydrating agent, PCl5 finds
numerous applications in organic chemistry:
- It acts as a chlorinating agent in organic synthesis by transferring chlorine
to organic substrates. This allows preparation of alkyl chlorides, acid
chlorides, and other chloro-organic compounds.
- PCl5 is extensively used for the industrial production of phosphate esters
which are used as plasticizers, flame retardants, lubricants, and hydraulic
fluids.
- It is employed for the manufacture of phosphonium salts through reaction with
tertiary amines or phosphines. These salts find use as phase transfer
catalysts.
- As a strong dehydrating and phosphinating agent, PCl5 is used to prepare
phosphonic acid dichlorides and thiophosphoric acid dichlorides.
- It is involved in the commercial production of organophosphorus pesticides
and herbicides like parathion and malathion through chlorination and
phosphination reactions.
- Other minor applications of PCl5 include use in the production of
semiconductors, pigments, and as a reagent in organic synthesis laboratories.
Safety Considerations
Due to its highly reactive and toxic nature, PCl5 demands special
precautions during handling and storage. It readily forms hydrochloric acid
upon contact with moisture in air. PCl5 is a severe irritant to eyes, skin and
respiratory tract. Inhalation of its vapors can cause sore throat, coughing,
and shortness of breath. Protective equipment like gloves, eye goggles and
masks must be used while working with it. Spills of PCl5 should be cleared
using damp sand or soda ash as it can ignite combustible materials on contact.
Proper ventilation is essential as its vapors are heavier than air and can
travel along ground level. Overall, as a crucial industrial chemical, safe
production and use of phosphorus pentachloride is important considering its
toxicity.
PCl5 serves as a versatile intermediate in organic synthesis and industrial
chemicals manufacturing owing to its chlorination and dehydration abilities.
Strict adherence to safety guidelines is mandatory for its production, storage,
transportation and handling. Though hazardous in nature, pentachloride will
continue playing a pivotal role in numerous industries worldwide due to lack of
better alternatives for the chemical transformations it brings about.
Comments
Post a Comment