Towards the thermochemical data of adducts involving glycine and cadmium chloride

摘要

The prepared adducts CdCl_2.xgly (x=1,2 and gly=glycine) were characterized by infrared spectroscopy, thermogravimetry and differential scanning calorimetry. The infrared spectra showed that cadmium is coordinated through the carbonyl oxygen and the nitrogen atoms in the monoadduct and only carbonyl groups are involved in the bisadduct. The monoadduct melted before thermal degradation, suggesting the existence of a weaker intermolecular force as confirmed by standard molar enthalpy of dissolution values of 16.47 +- 0.01 and 28.94 +- 0.01 kJ mol~(-1) for 1:1 and 1:2 adducts, respectively. The standard molar enthalpy of reaction in the condensed phase: CdCl_2(c) + xgly(c) = CdCl_2.xgly(c); #DELTA#_rH_m~#theta#, gave -9.52 +- 0.05 and -8.10 +- 0.01 kJ mol~(-1) and the interaction in aqueous medium: CdCl_2(ap) + xgly(aq) = CdCl_2.xgly(aq); #DELTA#_aqH_m~#theta#, gave -0.13 +- 0.07 and 0.00 +- 0.14 kJ mol~(-1) for CdCl_2.2gly, respectively. From #DELTA#_rH_m~#theta# values the standard molar enthalpies of formation of the adducts were calculated as -912.48 +- 6.60 and -1444.4 +- 13.60 kJ mol~(-1). The enthalpies of decomposition 130.5 +- 10.8 and 209.3 +- 8.4, lattice -190.7 +- 0.1 and 271.9 +- 21.6 and reaction in the gaseous phase 599.8 +- 16.8 and -329.3 +- 5.0 kJ mol~(-1) for CdCl_2.gly and CdCl_2.2gly adducts were also calculated. From data of the reaction in the gaseous phase the mean enthalpy of the cadmium-oxygen bond was calculated as 82.3 +- 5.0 kJ mol~(-1) for the bisadduct, which was restricted for a monoadduct due to the presence of distinct isomers.