Thermochemistry of the compounds M(C₄H7O5)x.nH2O(s) (x = 1 and 2, n = 1 and 0) of several kinds of biologically active metal ions (M = Na, K, Mg and Ca) with L-threonic acid

Abstract

The constant-volume energies of combustion (ΔCU ) of the solid hydrated L-threonate, M(C₄H₇O₅)xΔnH₂O(s) (M = K, Na, Mg and Ca; x = 1 and 2; n = 1 and 0), have been determined to be ΔcU [Na(C₄H₇O₅)ΔH₂O, s] = –(10241.95±5.14) J g⁻¹, ΔcU [K C₄H₇O₅).H₂O, s]=–(9103.12±4.71) J g⁻¹, ΔcU [Mg(C₄H₇O₅)₂. H₂O, s] = –(10407.34±4.67) J g⁻¹ and ΔcU [Ca(C₄H₇O₅)₂.H₂O, s] = –(10097.09 ± 5.26) J g⁻¹ by an RBC-II precision rotating-bomb combustion calorimeter at 298.15 K. The standard molar enthalpies of combustion of these compounds ( ) have been calculated to be: –(1802.38±0.91), –(1748.47±0.91), –(3383.07 ± 1.21) and –(3130.65 ± 1.21) kJ•mol⁻¹. The standard molar enthalpies of formation of these compounds (ΔfHºm ) have been derived to be: –(1265.84±1.06), –(1292.59±1.06),–(2571.68±1.63) and –(2653.34±1.08) kJ•mol⁻¹ from the combination of the standard molar enthalpies of combustion of these compounds with other auxiliary thermodynamic quantities.