A new nuclear magnetic resonance algorithm to determine equilibrium constants of the species in the B(III)–H 2O system

Abstract

Several efforts have been attempted to study species formation by Nuclear Magnetic Resonance (NMR) in systems with several chemical equilibria present. The majority of these are qualitative and only a few have tried to relate component fractions of a distribution diagram with experimental area fractions determined from NMR spectra to obtain equilibrium constants values. In this work we present a new focus that attempts to relate the species concentration fractions in the system with area fractions beneath NMR peaks to achieve this task. 11B-NMR data of B(III)–H 2O systems have been processed with the aid of formation constant values (−log * β) obtained by potentiometry which are 9.17±0.01 for B(OH) 3, 9.79±0.08 for B 2O(OH) 5 −, 19.90±0.09 for B 3O 3(OH) 4 − and 38.50±0.04 for B 5O 6(OH) 4 −, form B(III)–H 2O systems with 0.075 M≤[B(III)] total≤0.700 M, in agreement with previous reports and NMR behavior. The treatment of NMR data developed in this work gives a new methodology to obtain formation constants and suggests the possibility to establish a generalization of Beer's law to NMR spectroscopy.