Recovery time reduction to decrease experimental duration (R2D2): A simple and universal method to accelerate NMR experiments

Abstract

Acceleration techniques for one dimensional Nuclear Magnetic Resonance (1D NMR) are very useful, both for NMR enthusiasts and for chemists that use NMR for structural elucidation. To the latter, such techniques need to be straightforward. Recovery time Reduction to Decrease the experimental Duration (R²D²) relies on the incremental reduction of a pulse sequence's Recycle Time (TR). A pseudo-2D spectrum is acquired and after two Fourier transform, extraction and addition of the central rows, a 1D spectrum is obtained. Not only can it be applied to any pulse sequence that contains a TR, but it also requires only a list of recovery times and 2D processes to operate. With this method, we were able to easily reduce the experimental time by a factor of 2 and up to 4 using single-pulse, APT and DEPT ¹³C sequences. Moreover, R²D² has the potential to be used on other low abundance nuclei (such as ¹⁵N or ²H) and numerous other pulse sequences.

Keywords: (13)C NMR 1D spectra; Experimental time; Linear prediction; Structural elucidation; recovery time reduction.