Phosphorus trichloride(PCl3)
Phosphorus trichloride is a compound of phosphorus and halogen chlorine. PCl3 is commercially the most significant compound and is used to prepare a wide variety of products, including soaps, detergents, plastics, and insecticides.
Phosphorus trichloride with a lone pair of electrons acts as a Lewis base and forms adducts with lewis acids.
Preparation
Phosphorus trichloride is prepared industrially by the reaction of chlorine with a refluxing solution of white phosphorus in phosphorus trichloride, with continuous removal of PCl3 as it is formed.
In the laboratory it may be more convenient to use the less toxic red phosphorus.
Action of PCl3 with Water
General properties
The phosphorus in PCl3 is often considered to have the +3 oxidation state and the chlorine atoms are considered to be in the -1 oxidation state. Most of its reactivity is consistent with this description.
PCl3 is a precursor to other phosphorus and organo-phosphorus compounds.
PCl3 reacts rapidly with water to form phosphorus acid H3PO3 and HCl it is an exothermic reaction.
Triphenyl phosphite
A large number of similar substitution reactions are known, the most important of which is the formation of phosphite esters by reaction with alcohols or phenols.
with phenol, triphenyl phosphite is formed.
An industrially relevant reaction of PCl3 with amines is phosphonomethylation, which employs formaldehyde.
Amino phosphonates are widely used as sequestering and antiscale agents in water treatment. The large volume herbicide glyphosate is also produced this way.
TriPhenyl phosphine
The reaction of PCl3 with Grignard reagents and organolithium reagents is a useful method for the preparation of organic phosphines with the formula R3P (sometimes called phosphines) such as triphenylphosphine, Ph3P.
Under controlled conditions PCl3 can be used to prepare PhPCl2 and Ph2PCl.
The Lewis basicity of PCl3 is exploited in one useful route to organophosphorus compounds using an alkyl chloride and aluminum chloride:
The RPCl+3 product can then be decomposed with water to produce an alkylphosphonic dichloride RP(= O)Cl2.