EXTRACTION BY N,N,N',N'-TETRAALKYL-2-ALKYL-PROPANE-1,3-DIAMIDES .1. H2O, HNO3 AND HCLO4

The extracting properties of substituted diamides were investigated. The auto-association of N,N'-dimethyl dibutyl tetradecyl malonamide (DMDBTDMA) : (C4H9(CH3)NCO)2CHC14H29 in benzene and in TPH (aliphatic hydrocarbon) was shown by NMR using mass-action model. The degree of aggregation depends on the diluent, the diamide concentration and the acidity. The extraction of HNO3 and HClO4 was investigated by distribution measurements and IR spectroscopy. HNO3 extraction is explained by the competing formation of four adducts : L2.HNO3, L.HNO3, L.(HNO3)2, L.(HNO3)3 whose the equilibrium constants for 0,72 mol.l-1 amide in TPH are 0.167 , 0.215 , 5.19.10(-3) and 3.7.10(-4), respectively, on a molal scale. HClO4 is extracted by a reaction involving the competing formation of the two adducts L2.HClO4 and L.HClO4. Their equilibrium constants for 0.697 mol.l-1 amide in TPH are 0.649 and 1.71, respectively, on a molal scale. Nu(C=O) IR absorption shifts indicate that in L2.HNO3 and in L.HNO3, DMDBTDMA and HNO3 are linked by hydrogen bonds, whereas in L.(HNO3)2, L.(HNO3), and in L.HClO4 one H+ is transferred from one molecule of acid to one C=O of the DMDBTDMA. The different behavior of HClO4 and HNO3 can be attributed to their different acid strength, HClO4 being a much stronger acid than HNO3. The proton transfer from HNO3 to the diamide depends on the dielectric constant of the organic medium, the higher values being favourable to ion-pair formation. Oxalic acid is only weakly extracted by DMDBTDMA.