| The methods on syntheses of compounds of L-threonic acid and metal ion were discussed in this paper. Based on the literature, the methods concerning the preparation of 5 metal L-threnate were developed and innovated, involving NaC4H7O5-H2O, KC4H7O5-H2O, Mg(C4H7O5)2-H,O, Ca(C4H7O5)2, Zn (C4H7O5)2. And four new compounds of Mn(C4H7O5)2-H2O, Co(C4H7O5)2-H2O, Ni(C4H7O5)2-2H2O, Cu(C4H6O5)-0.5H2O were prepared as well.The compositions of 9 compounds were identified as, by chemical and elemental analyses, Na(C4H7O5)-H2O (1); K(C4H7O5)-H2O (2); Mg(C4H7O5)2-H2O (3); Ca(C4H7O5)2 (4); Mn(C4H7O5)2-H2O (5); Co(C4H7O5)2-H2O (6); Ni(C4H7O5)2-2H2O (7); Cu(C4H6O5)-0.5H2O (8); Zn(C4H7O5)2 (9). The title compounds were characterized by IR and TG-DTG. The bonding characteristics of the compounds were discussed and their structure were speculated from the results of the IR analyses, compounds 1 and 2 can be assumed as the simple carboxylic salts. As for compounds 3 to 8, M2+ coordinates to oxygen atom of the carboxyl group, while the proton of the carboxyl group is dissociated. it was assumed that the coordination number of M2+ was 4. M2+ in Compound $ coordinated to oxygen atom of the carboxyl group and oxygen atom of a - hydroxy, while the proton of the a - hydroxy was dissociated. The thermo stability of the compounds was studied by TG-DTG. The result of TG-DTG indicated that all of the compounds were of good stability. Their possible decomposing processes were also investigated, the final products of the thermal decomposition of the compounds were metal oxides.The constant volume combustion energy, cE, of the compounds were determined byRBC- II precise rotating-bomb calorimeter, their standard enthalpies of combustion, and standard enthalpies of formation, were calculated respectively. The results are (kJ.mol-1) : cE: -1803.62± 0.91(1); -1 749.71 ±0.91 (2); -3384.30±1.21(3);-3133.12± 1.63(4); -3384.30±1.21(5); -3504.47 ±1.64(6);-3515.22±1.97(7); -1616.15± 0.72(8); -2 853.14±1.49 (9). : -1 802.38±0.91 (1); -1748.47 ± 0.91(2); -3383.07±1.21(3);-3 130.65±1.63 (4); -3383.07±1.21(5); -3 501.99± 1.64 (6);-3512.74±1.97(7); -1 616.77±0.72 (8); -2 850.66±1.49 (9). : -1 265.84± 1.06(1); -1292.56±1.06 (2); -2 571.68± 1.63 (3);-2653.34±1.08(4); -2 571.68±1.63 (5); -2 170.67±1.97 (6),--2 447.51±2.26 (7); -1 114.76±0.81 (8); -2 648.69±1.11 (9). The heat capacity of compounds 1 and 2 was precisely determined with a small sample precision automated adiabatic calorimeter over the temperature range from 70 to 580 K. It was found that there was a s-s phase transition in compound 1 at about (311.441 ±0.221) K from the experimental molar heat capacity curve of the compound 1 with temperature. The molar enthalpy, mH and entropy, mS of the phase transition were (5.753±0.006) kJ-mol-1, (18.473 ± 0.016) J.K-1.mol-1, which were calculated on the basis of the heat-capacity measurement. Its melting point was (371.274 ±0.080) K, the molar enthalpy, H, and entropy, fusS, of the phase transition were (15.353 ±0.027) kJ.mol-1, (41.352±0.078) J.K-1.mol-1. The experimental molar heat capacity curve of the compound 2 with temperature showed the melting point of compound 2 was (3 80.524± 0.093) K. According to the heat-capacity measurement, the molar enthalpy, , and molar entropy, fusS, of the phase transition were calculated to be (19.655 ±0.012) kJ-mol-1, (51.618 ± 0.051) J.K-1.mol-1, respectively. |
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