Process for brominating unsaturated organic compounds using a quaternary phosphonium tribromide as the brominating agent
View Patent ↗Compounds or polymers that contain carbon-carbon unsaturation are brominated using a quaternary phosphonium tribromide as the brominating agent. The bromination process proceeds easily under mild conditions. The process can be highly selective. When the substrate is a butadiene polymer or copolymer, the brominated product tends to have excellent thermal stability.
1. A process for brominating a butadiene polymer or copolymer containing at least 10% by weight polymerized butadiene, comprising contacting at least one quaternary phosphonium tribromide and the butadiene polymer or copolymer under conditions such that at least 50% of the butadiene units of the butadiene polymer or copolymer become brominated.
2. The process of claim 1 , which is conducted in the presence of a solvent for the butadiene polymer or copolymer.
3. The process of claim 1 , wherein the quaternary phosphonium tribromide is a tetraalkylphosphonium tribromide.
4. The process of claim 3 , wherein the tetraalkylphosphonium tribromide is tetramethylphosphonium tribromide, tetraethylphosphonium tribromide, tetra(n-propyl)phosphonium tribromide, tetra(n-butyl)phosphonium tribromide, tetrahexylphosphonium tribromide, tetraoctylphosphonium tribromide, tri(hexyl)tetradecyl phosphonium tribromide, or a mixture of any two or more thereof.
5. The process of claim 1 , wherein the butadiene polymer or copolymer is a block copolymer containing one or more polystyrene blocks and one or more polybutadiene blocks.
6. The process of claim 5 , wherein the quaternary phosphonium tribromide is a tetraalkylphosphonium tribromide.
7. The process of claim 6 wherein the tetraalkylphosphonium tribromide is tetramethylphosphonium tribromide, tetraethylphosphonium tribromide, tetra(n-propyl)phosphonium tribromide, tetra(n-butyl)phosphonium tribromide, tetrahexylphosphonium tribromide, tetraoctylphosphonium tribromide, tri(hexyl)tetradecyl phosphonium tribromide, or a mixture of any two or more thereof.