THERMOCHEMICAL PROPERTIES OF RARE-EARTH CHLORIDE WITH DL-ALANINE

Combustion energies have been determined for the 24 solid complexes of rare-earth chlorides with DL-alanine: RE(Ala)Cl-3 . 6H(2)O (I) (RE=Eu -Ho, Yb, Y), RE(Ala)(2)Cl-3 . nH(2)O (II) (RE=La-Nd, Sm, n=3; RE=Ho, T o, Y, n=4) and RE(Ala)(3)Cl-3 . 3H(2)O (III) (RE=La-Nd, Sm-Dy). The st andard enthalpies of combustion, Delta(c,oor)H(0), and standard enthal pies of formation, Delta(f,coor)H(0), have been calculated for these c omplexes. The relationship of Delta(f,coor)H(0) with the ionic radius of rare-earth cations has been examined. The results show that a certa in amount of covalence is present in the chemical bond between the rar e-earth cation and DL-alanine. (C) 1998 Elsevier Science B.V.