Towards the thermochemical data of adducts involving glycine and cadmium chloride

The prepared adducts CdCl2. xgly (x = 1, 2 and gly = glycine) were characte rized by infrared spectroscopy, thermogravimetry and differential scanning calorimetry. The infrared spectra showed that cadmium is coordinated throug h the carbonyl oxygen and the nitrogen atoms in the monoadduct and only car bonyl groups are involved in the bisadduct. The monoadduct melted before th ermal degradation, suggesting the existence of a weaker intermolecular forc e 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: CdCl2(c) xgly(c)= CdCl2. xgly(c); Delta(r)H(m)(theta) gave -9.52 + /- 0.05 and -8.1 0 +/- 0.10 kJ mol(-1) and the interaction in aqueous medium: CdCl2(aq) + xg ly(aq) = CdCl2. xgly(aq); Delta(aq)H(m)(theta), gave -0.13 +/- 0.07 and 0.0 0 +/- 0.14 kJ mol(-1) for CdCl2. gly and CdCl2. 2gly, respectively. From De lta(r)H(m)(theta) values the standard molar enthalpies of formation of the adducts were calculated as -912.48 +/- 6.60 and -1444.40 +/- 13.60 kJ mol(- 1). The enthalpies of decomposition 130.5 +/- 10.8 and 209.3 +/- 8.4, latti ce -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 CdCl2. gly and CdCl2. 2gly add ucts were also calculated. From data of the reaction in the gaseous phase t he 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. (C) 1999 Elsevier Science Inc. All rights reserved.