Deuterium-induced shift

A11 shifts are indicated in ppm from TMS. The deuterium induced shift numbers are in parenthesis upon exchange with D2O. Negative values indicate upfield shifts. 

Labelled carbohydrates have been used to study deuterium-induced shifts. New assignments were made for shifts in isomaltose and glucosamine. A discussion of the n.m.r, spectra of several partially and fully acetylated L-rhamnose derivatives has appeared, including much tabulated data. ... 

The introduction of isotopes into a compound alters the coupling pattern and the chemical shifts of the observed spectrum. As shovm in Eigure 1.18, deuterium-induced chemical shift variations have allo ved the estimation of the ratio of isomers 90a-d formed in Eq. (2) vhen R = Ph, R = CHjCOOH, and DCOOD/ Et3N is used for the hydrogen transfer [136]. The three sp -carbons Cl, C2 and C3 each afford a distinct singlet for the four possible isotopomers 90a-d (replacement of by shifts the resonances of the adjacent carbon nuclei to lo ver frequency) [137]. 

A similar situation occurs in acetyl fluoride, where the nonlinearity of deuterium-induced isotope shifts on the 19F NMR signal implies a fractional population >1/3 for the conformer of CH2DCOF with C-D anti to F (38) and a fractional population <1/3 for the conformer of CHD2COF with C H anti to F (39).109 These populations arise because of the greater zero-point energy of a C H bond anti to F. They can be translated into deuterium IEs on the acidities of the conformers of acetyl or acetyl-d fluoride. 

According to deuterium-induced upfield H NMR isotope shifts in partially deuterated rigid cyclohexane-1,3-diols dissolved in CDC13 or benzene-c/6, the OH is preferentially solvent-exposed, while deuterium prefers to reside in the intramolecular hydrogen bond (49).121 In acetone-c/6 and DMSO-c/6 downfield isotope shifts indicate that the OH preferentially resides in the intramolecular hydrogen bond, while OD forms an external hydrogen bond to the acceptor solvent, S (50). 

An early report (2) on steroid 13C NMR includes discussion of the carbon chemical shifts of model compounds, single-frequency off-resonance decoupling, induced shifts upon acetylation, and deuterium exchange. These techniques are all amply reviewed by Blunt and Stothers (1) and are not specifically treated here. A particularly readable account of the off-resonance decoupling experiment is given in the text by Wehrli and Wirthlin. (3)... 

The replacement of hydrogen atoms with deuterium caused large deuterium-induced isotope shifts in the 77Se NMR. For both conformers 45 and 46, the resonance of the deuterated compound shifted upfield with respect to the parent compound. The isotope shift (AS, an upfield shift) was 4.22 ppm for 45 and 4.03 ppm for 46. These values were definitely larger than that observed for 46 (AS = 3.78 ppm). These differences, AAS = +0.44 ppm for 45 and +0.25 ppm for 46, can be considered as the isotope shifts due to the C-H- -Se nonbonded interaction <1996BCJ1825>. 

Also known are the deuterium-induced isotope effect on the Sn shielding of —0.05 ppm/D and the primary isotope effect of —11.6 7 Hz for Sn—H spin-spin coupling for the SnDnH3 + cations generated in fluorosulfuric acid at low temperature from SnD H4 . The chemical shift of 208 ppm found in the Sn NMR of the reaction mixture of Me4Sn and SbCls was attributed to the Me3Sn+ cation. 

Recently, deuterium-induced isotope effects on Li chemical shifts in organolithium compounds have been observed [51] and based on this observation, the isotopic fingerprint method was developed as a tool for structural investigations in the field of organolithium compounds. With this method, typical Li multiplets, which are characteristic of the aggregation state. 

Figure 5 Deuterium-induced isotopic fingerprints in Li NMR spectra of partially deuteriated organolithium aggregates (a) phenyllithium monomer (THF/penta-methyldiethylenetriamine — 122°Q (b) phenyllithium dimer (Et20/tetramethylethyl-enediamine -111°C) (c) methylhthium tetramer (R=CHj EtjO, — 92 Q (d) fluxional phenyllithium tetramer (Et20, — 102 C). The measu H/ H isotope shifts for 5( Li) are 19.2, 10.4, 15.6, and 7.0 ppb, respectively. All systems were Li labelled and 50% of the organic ligands were perdeuterated v C Li) = 58.88 MHz...

The most important NMR parameters obtained for the hydroxyl protons are chemical shifts (6), vicinal proton-proton coupling constants (3J7hc,Oh), temperature coefficients (AS/7), deuterium-induced differential isotope shifts, and exchange rates ( ex)-119-123 These parameters may provide information on hydrogen bond interactions and hydration as well. Moreover NOEs and chemical exchanges involving hydroxyl groups observed by NOESY and ROESY experiments also add to the number of distance restraints used in conformational analysis. 

CP/MAS), gated H-decoupling techniques, deuterium-induced isotope effects chemical shifts, and molecular modeling has shown that this... 

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