0000000000214638
AUTHOR
Marie-josé Schwing
(o-Hydroxyphenyl)methylphosphonic Acids: Spectrophotometric determination of their pKavalues and of the deprotonation sequence
UV/VIS Absorption spectra of nitrosubsituted (o-hydroxyphenyl)methylphosphonic acids (o-(phosphonomethyl)phenols) were measured as a function of pH at 25° in 0.1M NaClo4 solutions. Computational treatment of the whole set of optical density data between 200 and 500 nm resulted in the determination of the dissociation constants of these polyacids and also of the individual electronic spectra of all the species involved in the deprotonation sequence. The spectral behavior gives information on the structure of the anions formed and consequently the order of the subsequent deprotonation steps could be deduced. For the (2-hydroxy-3-nitro(or 5-nitro)phenyl)methylphosphonic acid and the 2-hydroxy-…
(o-Hydroxyphenyl)methylphosphonic acids: Synthesis and potentiometric determinations of their pKaValues
(o-Hydroxyphenyl)methylphosphonic acids are readily obtained from o-(bromomethyl)- or o-(hydroxymethyl)phenols and trialkyl phosphites. Subsequent hydrolysis leads to the corresponding phosphonic acids. For a series of such compounds, the pKa values have been determined by potentiometry. Their dependence on additional substituents in the aromatic ring is discussed in terms of electronic and steric effects.