6533b7d8fe1ef96bd126ab43

RESEARCH PRODUCT

Polymere ester von Säuren des phosphors, 5. Ringöffnende polymerisation des 2-phenoxy-1,3,2-dioxaphospholan durch Michaelis-Arbuzov-reaktion

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2-Phenoxy-1,3,2-dioxaphospholane (14) was polymerized by benzyl halogenides at temperatures between 120 and 200°C. It was found that the main chain consists predominantly of unexpected ethylene 1,2-ethanediphosphonate units 7; only about 10% of the monomer was incorporated as the expected 2-hydroxyethanephosphonate structure. An insertion mechanism, proposed by Harwood and Patel for the analogous polymerization of 2-phenyl-1,3,2-dioxaphospholane, does not agree with our experimental results. A hypothesis is developed involving a two step addition process, which exclusively occurs at the chain end. Alternating, one monomer molecule is added by a normal Michaelis-Arbuzov-reaction, and then a second molecule is added followed by an intermediate 1,2-shift of the endstanding halogen cryptoanion. With benzyl bromide as initiator, the growing end shows alternating the sequences CPOCCBr (2-bromoethyl ester) and COPCCBr (2-bromoethanephosphonate).