REACTIONS OF AMIDES AND RELATED COMPOUNDS: I. N.M.R. (PROTON) INVESTIGATION OF <i>N</i>,<i>N</i>-DIMETHYLFORMAMIDE – LEWIS ACID ADDUCTS AND REMARKS ON THE RELATIVE STRENGTH OF LEWIS ACIDS

Abstract

The proton resonance spectra of a number of Lewis acid – N,N-dimethylformamide adducts in 2-nitropropane and methylene chloride solutions have been investigated and an attempt has been made to correlate the relative strength of Lewis acids with the chemical shift of the methyl protons. The order obtained for the relative strength of Lewis acids shows good agreement with the results obtained by other methods. The complex formation has taken place on the carbonyl oxygen of the N,N-dimethylformamide in all cases. The DMF – Lewis acid mole ratios were 1:1 in ZnCl 2 , AlCl 3 , PF 5 , BiCl 3 , InCl 3 , AsF 5 , SbCl 5 , SbF 5 , BF 3 , BCl 3 , BBr 3 . The 2:1 DMF – Lewis acid complexes of ZnCl 2 , SnCl 4 , SnBr 4 , Snl 4 , TiCl 4 , ZrBr 4 have also been investigated.