Utilities of No-D NMR (No-Deuterium Proton NMR)

No-D NMR (No-Deuterium Proton NMR) technique is a measurement of high resolution ¹H NMR spectra without deuterium solvent. It suggests that any reaction mixture or reagent solution are directly available for No-D NMR measurement. In conventional NMR measurements, ²H signals of deuterium solvent are used for the shimming, however ¹H solvent signals are as well in No-D NMR measurements. Since suppression of strong ¹H solvent signals by WET eliminates ¹³C satellite signals also, it is convenient approach to collect ¹H NMR spectra without deuterium solvent by No-D NMR measurement.

Automation script for No-D NMR

The following 5 steps are automated No-D NMR measurement procedure on NMR software Delta, and every tedious measurement parameters are automatically adjusted.

• ① Shimming
• ② Detecting solvent signals
• ③ Suppression of solvent signals
• ④ Processing FID data
• ⑤ Chemical shift adjustment

On Delta software, chemical shift in the conventional ¹H measurement is not adjusted without NMR lock (Fig. 1a), but the automation of No-D NMR adjusts chemical shift automatically (Fig. 1b). Its result has the same chemical shift information as deuterated solvent sample spectrum (Fig. 1c).

Fig.1 ¹H spectra of 5 mg rotenone measured with JNM-ECZ500R

For starting No-D NMR measurement, only simple 2 parameters are required (Fig.2).

• Select solvent
• Input the number of suppression signals

Fig.2 Operation window of No-D NMR (Delta V5)

Application of No-D NMR 1: Observation of exchangeable ¹H signals

When the compound with exchangeable proton is dissolved in exchangeable proton solvent (D₂O, CD₃OD, and etc.), proton atom is replaced with deuterium atom. As results, it is not possible to observe amino protons for the target molecule (Fig. 3 upper). On the other hand, the exchangeable proton can be observed in No-D NMR, since amino protons are kept under protonated solvent (Fig. 3 bottom).

Fig.3  2.5mg L-Tryptophan measured with JNM-ECZ600R

Application of No-D NMR 2:  Apply to mixed solvent

Because No-D NMR can suppress multi site signals, it is also effective for multi signal solvents  such as CH₃OH and mixed solvent sample.
Furthermore,  ¹³C decoupling is useful, when solvent ¹³C satellite signal overlap with sample signal.  Fig.5 indicates how sample signal can be distinguished from ¹³C satellite by ¹³C decoupling. Chemical shifts in Fig.4 and Fig.5 are intentionally  adjusted for better clarity.

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