In order to compare the calculated chemical shifts with experimental ones, it is important to use consistent nuclear shieldings for NMR reference compounds like TMS. The influence of rotating functional groups X=CH3, CHO, NO2, NH2, CONH2, COOH or C6H5 on the shielding tensors in seven ...
By matching the rotational resonance condition (delta = n omega r/2 pi, where delta is the difference in isotropic chemical shifts for two dipolar coupled spins, omega r/2 pi is the mechanical rotational frequency of the sample in the MAS experiment, and n is a small integer denoting the ...
This anisotropic effect on the 1H chemical shifts of the methyl protons has been quantified on the basis of through-space NMR shieldings (TSNMRS) and subsequently Δδ calcd compared with the experimentally observed chemical shift differences, Δδ exp. In this context, the experimental anisotropic...
An analysis of selected sets of metallaboranes in terms of a molecular orbital (MO) model of 11B chemical shift change is used to demonstrate the origin of transition metal effects on boron shifts for: (i) M-B edge protonation; (ii) replacement of direct B-B by M-B interactions; (iii...
CHESCA-CL implementations are applied to the nitrogen and proton chemical shifts using a 0.95 |rij| cutoff value (H- and N-CHESCAs) and only the residues that are conserved between the two complete-linkage clusters generated by the H- and N-CHESCAs are included in the functional network. ...
OXYGEN-17 NMR CHEMICAL SHIFTS OF ALCOHOLS, ETHERS AND ESTERS The 17O NMR chemical shifts of alcohols, ethers and esters have been determined in natural abundance at 10.8 MHz. As the alkyl groups are changed, shielding of oxygen atoms decreases in the order: primary 17O shifts of these compou...
The method is based on using the differences in CαH proton chemical shifts which result from peptide sequence nearest-neighbor and possibly secondary structure effects to resolve resonances for carbon-bonded reporter protons adjacent to each side-chain acidic group in two-dimensional total correlation...
•Ascanbeseenfromtheformula,ethylacetatecontainstwodifferentmethylgroups,thechemicalshiftsofwhich,asexpected,aredifferent.Onemethylgroupisattacheddirectlytothecarbonylgroup,andtheothertothemethylene(-CH2-)group.However,theappearancesofthesignalsbelongingtothesemethylgroupsarecompletelydifferent.•Whilethemethylgroup...
NMR chemical shifts are exquisitely sensitive to the local environment, and we show here that NMR can clearly distinguish binding (which produces a typical saturation curve) from solvent interactions (which are individually much weaker interactions and produce linear shift changes). The method is ...
A study of the 13 C-NMR spectra of compounds of each of these types and of simple and more complex mixtures has shown that each ester type has characteristic chemical shifts for the three glycerol carbon atoms and for C1 and C2 in each acyl chain. This information allows easy identification...