A polarimetric and 11B and 13C nuclear magnetic resonance study of the reaction of the tetrahydroxyborate ion with polyols and carbohydrates

Abstract

The reaction of the tetrahydroxyborate ion, B(OH);, with 31 polyols and carbohydrates in aqueous solution has been studied by complementary investigations involving polarimetry and llB and 13C n.m.r. spectroscopy. The calculation of equilibrium constants for the complexation of the carbohydrates with B(0H); from the polarimetry results, using a previously derived equation, was only partially successful owing to the presence of multiple equilibria in a number of cases. The presence of several complexed species in these reactions is demonstrated by llB n.m.r. studies. A calibration method devised to relate peak area in llB n.m.r. spectra with concentration has been used to calculate equilibrium constants for the various equilibria present, and an attempt has been made to rationalise the equilibrium constants with the molecular structures of the substrates. In the majority of cases the 13C n.m.r. spectra confirm the polarimetric and llB n.m.r. studies, and in most cases allow a more specific identification of the reaction sites in the polyols/carbohydrates to be made.

Separation of glycols from dilute aqueous solutions via complexation with boronic acids

“…In summary, as chain length of the diol increases, complexation becomes stronger, with inner CHOH groups favored over terminal CHzOH groups. This phenomenon has been postulated to be related to the reduced freedom of rotation of the inner hydroxyl groups (Conner and Bulgrin, 1967;Dawber et al, 1988).…”

“…For both 1,2=ethanediol and 1,2-propanediol, stability constants obtained by Pail (1975Pail ( , 1976Pail ( , 1977 and Roy et al (Roy, Laferriere, and Edwards, 1957) across alternate carbons are: I11,1---3.5 (Dawber et al 1988);111,1--"3.7, 111,2" 0.05 (van Duin et al, 1984).…”

“…Mechanistic and stereochemical data have been obtained through chromatography, electrophoresis, polarimetry, and spectroscopy, with B 11 NMR spectroscopy recently gaining popularity (Dawber and Green, 1986;Dawber et al, 1988;Oertel, 1972;Onak et al, 1959;van Duin et al, 1984van Duin et al, , 1985Weser, 1967 form. Since significant borate formation does not occur below the pK a of the acid (9.2 for boric acid), the anionic complex is formed primarily in basic solution (Boeseken, 1949;Henderson et al, 1973;Weser, 1967).…”

“…complexes for both 1,2= and 1,3=diols (Dawber and Green, 1986;Dawber et al, 1988;Henderson et al, 1973;Oertel, 1972;van Duin et al, 1984van Duin et al, , 1985. Further, Oertel's Raman data give direct evidence for the chair conformation for the 1,3-dioi-borate complex.…”

The Stability Constants and Thermodynamic Parameters of Borate - Carbohydrate Complexes by pH Measurements

“…The study of the formation of complexes between borate and polyhydroxy compounds has been received considerable attention since few decades [1][2][3] . Such studies provide an important tool in conformational analysis of carbohydrates and are used in a variety of separation and chromatographic techniques.…”