Basicité et structure de phosphoramides aliphatiques: dosage protométrique en solvants non-aqueux

Abstract

Brönsted basicities (as half-neutralization potentials) have been determined at 25 °C by potentiometric titrations in nitromethane or in the mixture sulfolane/benzene 98:2 p/p for 19 aliphatic phosphoramides OPXYZ, with X, Y, or Z = Me; OEt; NMe2; NEt2; NHEt; N(CH2)n (n = 3 or 4); or X + Y = —NMe—(CH2)2—NMe—. Almost all of these weak bases give an homohydrogen bonding. Those with an Me or N(CH2)3 substituent are not stable in acidic medium, which is confirmed by back-titration and measure of E vs. time at the equivalent point. After comparing the results obtained in the two solvents, the effect of the nature of the substituents X, Y, Z on half-neutralization potentials and instability in acidic medium is analyzed.