Chemical shifts conversion factors

Fig. 14.10 Structures and chemical shift assignments of calystegins monitored in root cultures of Calystegia sepium [79]. chemical shifts were reported relative to potassium N-nitrate. Chemical shifts in this figure have been referenced to liquid NH3 using 376.5 ppm, the chemical shift of sodium N-nitrate in water as the conversion factor.

Nicotinamide adenine dinucleotides have been studied at 10.14 MHz in D2O solutions (pH 7) at room temperature the chemical shifts of the pyridine fragment exhibit great changes during redox reactions which lead to rehybridization of the azine nitrogen (the shifts were originally referenced to 1M ND Cl in D2O conversion factor -352 ppm) (O 10). 

Table 6.42. chemical shifts of iminium, amidinium and guanidinium salts measured at 9.118 MHz, 301 K and originally referenced to NaNO, 2 (conversion factor = -1.5 ppm) 0.08m Cr(acac) was added to the solutions. (R13)... 

Chemical shifts (cs) are expressed in parts per million (ppm) downiield from a chosen reference signal of an added internal standard compound. Any of three different standard compounds are commonly employed to measure the proton shifts of nucleic adds in H2O or DjO solution DSS, TSP or TMA (see section 3.5.4.2). The frequency of the methyl protons of DSS and TSP (at pH 7) are hoth close to, but not identical with, the frequency of the common standard tetramethylsilane (TMS), employed in non-aqueous solvents. However, TSP is known to display a readfly measurable pH dependence [77D1]. The introduction of TMA followed a report [73L1] in which it was shown that the resonance position of DSS varied with the purine concentration. The central peak of the TMA signal is usually taken to resonate 3.18 ppm dowtfield from DSS. Since the exact shift difference tma dss depend upon various factors (purine concentration, temperature, ionic strength a conversion of one standard to another was not attempted in the present compilation. 

---