77144-03-7Relevant articles and documents
Reactivity and Mechanism of Hydrolysis of Phosphonamides
Rahil, Jubrail,Haake, Paul
, p. 1723 - 1734 (2007/10/02)
The rates of hydrolysis of three phosphonamides, N,N-dimethylphenylphosphonamide (XII), N-(phenylphosphonyl)pyrrolidine (XIII), and N-(phenylphosphonyl)morpholine (XIV), have been investigated.There is firs-order dependence on acidity in the pH range 4-7 with a pH independent region at low pHs, consistent with saturation due to complete formation of the neutral amide.The specific rate constant (k2) and the acidity constant (Ka) were obtained from the dependence of pseudo-first-order rate constants on +>; k2 is 1.27*10-2 s-1 and 1.42*10-3 s-1 and pKa is 4.8 and 5.3 for XII and XII, respectively.The small value of the acidity constants is consistent with predominant N-protonation.The activation parameters for XII are ΔH = 11.1 kcal/mol, ΔG = 20.35 kcal/mol, and ΔS 0 -31 eu.Solvent and salt effects on the rate of hydrolysis of XII are insignificant.The solvent isotope effect, k2(H2O)/K2(D2O), is 1.2 and Ka(H2O)/Ka(D2O) is 3.2.Fluoride ion catalyzed the rate of reaction of XII.The Broensted β value is about -1, implying rate-determining breakage of the P-N bond.The results appear to be most consistent with an SN2(P) mechanism.The reactivity of phosphorus amides is discussed in terms of their structure.
