Poly(4-vinylpyridine) Complexes with Bromine and Bromine Chloride as Reactive Polymers in Addition Reactions

The following general features of poly(4-vinylpyridine)-halogen complexes (PVP-XY; X = Br, Y = Br, Cl) were observed, when reacting with olefinic and acetylenic compounds, as compared with the free halogens under similar conditions of solvent and temperature: reactions took place at much slower rates, allowing in most cases mixing of the total amounts of reacting materials in the reactor; when inert solvents were used, the isolated crude adducts were nearly pure compounds; with PVP-BrCl only small amounts of dibromo or dichloro adducts were formed; side reactions frequently accompanying additions of free halogens to double and triple bonds, such as HBr evolution, were absent. When addition to double bonds was carried out in a reactive solvent such as acetic acid, one-fourth to one-third of the product was a bromo-acetate ad- duct, while addition to acetylenic compounds gave no such byproducts. After the halogen of the polymeric reagent was consumed, the polymer could be filtered and regenerated for reuse. PVP-XY undergoes quaternization reactions concurrently with halogen addition to double or triple bonds. Such reactions may also lead to further cross-linking of the PVP network. Analogous quaternizations using monomeric pyridine- halogen reagents and acetylenic substrates point to various possible quaternization paths of the polymeric reagent: N-vinylation of one pyridyl group, attachment of two N-pyridyl groups at the 1,2-positions of a vi- nylidene group, or further transformations of the quaternary compounds, depending on the nature of the acetylenic substrate.