ABSTRACT
A flavanone and a flavanone glycoside, together with vomifoliol, have been isolated for the first time from the aerial parts of the plant Echiochilon fruticosum and identified. Their structures were established on the basis of spectroscopic measurements, mainly 2D NMR using COSY, HMQC and HMBC experiments.
Subject(s)
Boraginaceae/chemistry , Butanols/chemistry , Butanols/isolation & purification , Cyclohexanones/chemistry , Cyclohexanones/isolation & purification , Flavanones/chemistry , Flavanones/isolation & purification , Glycosides/chemistry , Glycosides/isolation & purification , Carbon Isotopes , Magnetic Resonance Spectroscopy , Protons , TunisiaABSTRACT
The formation of hydroxo acetate complexes of iron (III) ion has been studied at 25 degrees C in 3 M (Na)ClO4 ionic medium by measuring with a glass electrode the hydrogen ion concentration in Fe(ClO4)3-HClO4-NaAc mixtures (Ac = acetate ion). The acetate/metal ratio ranged from 0 to 6, the metal concentration varied from 0.005 to 0.06 M, whereas [H+] was stepwise decreased from 0.1 M to initial precipitation of hydroxo-acetates. This occurred, depending on the acetate/metal ratio, in the -log[H+] range 1.85-2.7. The potentiometric data are consistent with the presence of Fe3(OH)3Ac3(3+), Fe2(OH)2(4+), Fe3(OH)4(5+), Fe3(OH)5(4+) and, as minor species, of Fe3(OH)2Ac6+, FeAc2+, FeAc2+, FeOH2+ and Fe(OH)2+. Previously published EMF measurements with redox and glass half-cells were recalculated to refine the stability constants of FeAc2+, FeAc2+ and Fe3(OH)2Ac6+. Formation constants *beta pqr for pFe(3+)+(q-r)H2O + rHAc reversible Fep(OH)(q-r)(Ac)r3p-q + qH+ (in parenthesis the infinite dilution value): log*beta 111 = -1.85 +/- 0.02 (-0.67 +/- 0.15), log*beta 122 = -3.43 +/- 0.02 (-1.45 +/- 0.15); log*beta 363 = -5.66 +/- 0.03 (-2.85 +/- 0.40), log*beta 386 = -8.016 +/- 0.006 (-4.06 +/- 0.15), log*beta 220 = -2.88 +/- 0.02 (-2.84 +/- 0.05), log*beta 340 = -6.14 +/- 0.18 (-6.9 +/- 0.4), log*beta 350 = -8.44 +/- 0.09 (-7.65 +/- 0.15).
Subject(s)
Acetates/chemistry , Ferric Compounds/chemistry , Chemical Precipitation , Oxidation-Reduction , Protons , TemperatureABSTRACT
The formation of oxalate and citrate complexes of the Sn2+ ion in 1 M Na(ClO4) at 25 degrees C was investigated in the -log[H+] range 2 to 5 by potentiometric titrations using glass and tin amalgam electrodes. The tin concentration was varied from 0.5 to 5 mM and the concentration of the ligands from 1 to 40 mM. The experimental data have been explained by the formation of the oxalato complexes SnC2O4(aq) and Sn(C2O4)2(2-) and of the citrate complexes (C3H5O7(3-) = citrate ion) SnC3H5O7-, SnHC3H5O7(aq), SnH2C3H5O7+ and Sn(OH)C3H5O7(2-). The equilibrium constants were refined by the computer program SUPERQUAD. The final values of the constants on the medium scale and in the infinite dilution reference state are given in Table 2.
