The reactions of some methylphosphorus(V) compounds with 25 oleum and 100% H2SO4

Abstract

The reactions of some methylphosphorus(V) compounds with the strongly acidic solvents 25 oleum (containing 25% free SO₃) and 100% H₂SO₄ have been investigated by ³¹P n.m.r. spectroscopy. Solvolysis is faster in 100% H₂SO₄ than in 25 oleum, and for P–Br than for P–Cl bonds. The ‘compounds’ PMeCl₂Br₂ and PMe₂ClBr₂ have been shown to contain mixtures of the corresponding halogenophosphonium cations PMeCl_nBr_{3 –n}⁺(n= 0–3) and PMe₂Cl_nBr_{2 –n}⁺(n= 0–2) in these solvents. Halogen exchange has been observed between PMe₂Cl₃ and PMe₂Br₅ in 25 oleum.