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Electronegativity And Resonance Effects On Identification Of Halogens By NMR, With Using DBM Derivatives And As Well A New La(III) Shift Reagent

S.N.Azizi, M.Hosseiny

A series of complexes of di-tert-butyl 1,3-acetone dicarboxilate and halogenated derivatives dibenzoylmethane (DBM) at ortho, meta and para positions of mono as well as biphenyl rings with praseodymium and europium have been synthesized as lanthanide shift reagents and the induced shifts (LIS) in 1H NMR spectra on n-pentanol have been studied. More interest is NMR studies of the electro negativity effects and as well the resonance effects of halogens. The order of electro negativity and steric effects of halogens and as well resonance and inductive effects of these substituents in phenyl rings of LSRs have been studied by the observed order of LIS which arises from these shift reagents. It has been observed that the induced shift of protons of n-pentanol increases along increasing of electro negativity effect of substituted halogens i.e. by inductive effects but the resonance effect decreases the induced shifts. And also the result of experiment, comparison the induced shifts of the meta substitution of halogens has shown electronegativity in order of F>Cl>Br>I, as well for the same situation substitution in both rings of DBM in chelate has shown more effect than the substitution in one ring in LIS. As well the resonance effects of halogens has been tested by this manner. A new LSR with using the di-tert-butyl 1,3-acetone dicarboxilate as a ligand has been synthesized and studied as a shift reagents. The lanthanide type and as well solvent effect in LIS also studied. Most lanthanide DBM complexes have been examined as possible shift reagent. A test on the effect of solvents has been done and it has been observed that LIS of the protons of n-pentanol decreases among the series CCl4>CDCl3>C6D6>(CD3)2CO.