THERMOCHEMISTRY OF LIQUID ADDUCTS OF AMIDES FORMED FROM ASX3 (X = CL,BR)

Liquid adducts of the general formula AsX3L (X=Cl, Br; L=N,N-dimethylf ormamide (DMF), N,N-dimethylacetamide (DMA), tetramethylurea (TMU)] we re synthesized and characterized by elemental analysis, IR spectroscop y and mass spectra. From enthalpies of dissolution (Delta(i)H(m)(0)) i n 1,2-dichloroethane at 298.15 K and the appropriate thermochemical cy cle, standard molar enthalpies have been determined for Lewis acid-bas e reaction (Delta(r)H(m)(0)), formation (Delta(f)H(m)(0)), decompositi on (Delta(D)H(m)(0) or Delta(M)H(m)(0)), Lewis acid-base reaction in g as phase (Delta(f)H(m)(0)) and the mean arsenic-oxygen bond enthalpies , [D] (As-O). These thermochemical parameters give the acidity AsCl3>A sBr3 and basicity TMU>DMA>DMF. (C) 1998 Elsevier Science B.V.