The DEPTQ+ Experiment: Leveling the DEPT Signal Intensities and Clean Spectral Editing for Determining CHn Multiplicities

Abstract

We propose a new 13C DEPTQ+ NMR experiment, based on the improved DEPTQ experiment, which is designed to unequivocally identify all carbon multiplicities (Cq, CH, CH2, and CH3) in two experiments. Compared to this improved DEPTQ experiment, the DEPTQ+ is shorter and the different evolution delays are designed as spin echoes, which can be tuned to different 1JCH values; this is especially valuable when a large range of 1JCH coupling constants is to be expected. These modifications allow (i) a mutual leveling of the DEPT signal intensities, (ii) a reduction in J cross-talk in the Cq/CH spectrum, and (iii) more consistent and cleaner CH2/CH3 edited spectra. The new DEPTQ+ is expected to be attractive for fast 13C analysis of small-to medium sized molecules, especially in high-throughput laboratories. With concentrated samples and/or by exploiting the high sensitivity of cryogenically cooled 13C NMR probeheads, the efficacy of such investigations may be improved, as it is possible to unequivocally identify all carbon multiplicities, with only one scan, for each of the two independent DEPTQ+ experiments and without loss of quality.