Preparation and properties of 1-bromo-2,2,3,4,4-pentamethylphosphetan 1-oxide, C8H16P(O)Br, and a comparison with the chloro-compound; hydrolysis of these to the anhydride and acid. Vibrational spectra
Abstract
The title compound can be prepared from the reaction of 2,4,4-trimethylpent-2-ene, phosphorus tribromide, and aluminium bromide in dibromomethane followed by controlled hydrolysis. The inclusion of material containing chlorine results in the production of the well known 1-chloro-analogue, C8H16P(O)Cl. The bromo-derivative has been fully characterized and its reactivity towards common nucleophilic reagents shows it to be more reactive than the chloro-compound. At room temperature both undergo slow hydrolysis to the corresponding acid, C8H16P(O)OH, whereas at higher temperatures the initial product is the anhydride, C8H16P(O)·O·P(O)C8H16. This compound is relatively resistant to further hydrolysis except by solution of pH > 12. Kinetic studies show that hydrolysis under these conditions is of the first order in both anhydride and OH–. Other ways of preparing the anhydride as well as its reactions have been studied. Raman and i.r. spectra of the bromide, chloride, acid, and anhydride are analysed; νs(POP) is identified.