The
Reed reaction is a chemical reaction that utilizes
photochemistry to
redox to alkylsulfonyl chlorides. This reaction is employed in modifying polyethylene to give chlorosulfonated polyethylene (CSPE), which is noted for its toughness.
Commercial implementations
Polyethylene is treated with a mixture of chlorine and sulfur dioxide under UV-radiation. Vinylsulfonic acid can also be prepared beginning with the
sulfochlorination of
chloroethane. Dehydrohalogenation of the product gives vinylsulfonyl chloride, which subsequently is hydrolyzed to give vinylsulfonic acid:
- :
- :=
- :==
Mechanism
The reaction occurs via a
free radical mechanism. UV-light initiates homolysis of
chlorine, producing a pair of chlorine atoms:
Chain initiation:
- :::Cl2 ->h\nu 2Cl.
Thereafter a chlorine atom attacks the hydrocarbon chain, freeing hydrogen to form hydrogen chloride and an alkyl free radical. The resulting radical then captures Sulfur dioxide. The resulting sulfonyl radical attacks another chlorine molecule to produce the desired sulfonyl chloride and a new chlorine atom, which continues the reaction chain.
Chain propagation steps:
- :::{R-H} + .Cl -> {R.} + HCl
- :::{R.} + {:}SO2 -> R-\dot{S}O2
- :::{R-\dot{S}O2} + Cl2 -> {R-SO2-Cl} + Cl.
See also
Historical readings
