chemical shift

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chem·i·cal shift

dependence of the resonance frequency of a nucleus on the chemical binding of the atom or molecule in which it is contained. See: chemical shift artifact.
Farlex Partner Medical Dictionary © Farlex 2012

chemical shift

An MRI term for a variation in the nominal Larmor frequency for a particular isotope within the imaging volume. The amount of chemical shift is directly proportional to the strength of the magnetic field, and is specified in parts per million of the resonant frequency.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.
References in periodicals archive ?
Normally carbon attached to phenolic -OH group appears at about 155 ppm, but, in these complexes, it was observed at 155-160 ppm which may be due to electron deshielding effect of zinc metal atom.
[sup.13]C NMR spectrum also supported the presence of amide group from the deshielding value of carbon attached to -CONH group at [delta] 169.3 ppm and carbonyl group (part of a five member ring) at [delta] 169.47 ppm.
The introduction of the more deshielding group in the latter compound shifted the adjacent protons downfield, the chiral proton from [[delta].sub.H] 4.26 to 4.74 and the methyl protons from [[delta].sub.H] 1.55 to 1.61.
The chemical shift value of the azomethine in the complexes were observed at downfield in comparison with that of the free ligand, suggesting deshielding of the azomethine proton due to is coordination to zinc(II) through the azomethine nitrogen (Fig.
The deshielding effect of electron-withdrawing carbonyl group and thiocarbonyl group has shifted the signal to downfield region [24].
The [sup.1]H NMR data of various axially ligated Zr(IV) compounds of [H.sub.2]TPP revealed that the presence of electron withdrawing groups like -N[O.sub.2], -Cl at paraposition of phenolate caused slight downfield shift (deshielding) and the presence of electron releasing group like -C[H.sub.3]> -N[H.sub.2] at paraposition of phenolate caused upfield shift (shielding) of protons with respect to Zr(TPP)(acac)(Oph) which have unsubstituted phenolate as an axial ligand.
The 1H NMR spectrum of every compound unveils the deshielding of NH of the triazole ring as anticipated in the range S 14.00-14.50.
The [.sup.13C] spectra of alkyl acrylates shows that with an increase in the size of pendant group, deshielding of [beta] unsaturated carbon decreases and it appears upheld in NMR.
A peak at 2.1 [delta] observed for methyl protons equivalent to 3H (Hd) sandwiched between silicon and silicic acid, shows deshielding of the methyl proton by two electron withdrawing groups and favours the geometry shown in Fig.
concentrations cause a nuclear deshielding, leading to noticeable
The peak of CSNH was at higher chemical shift due to deshielding effect [18].
The position of the azomethine signal in the complexes are downfield in comparison with that of the free ligand, suggesting deshielding of the azomethine proton due to is coordination to zinc through the azomethine nitrogen [2, 6].