Theoretical and Experimental APT and Dept Behavior of Methane

Abstract

The theoretically developed Attached Proton Test (APT) and Distortionless Enhancement by Polarization Transfer (DEPT) curves for methane were compared with the corresponding experimentally measured data for 13C enriched methane. As expected, in both cases the CH4 curves have a similar shape than the corresponding CH2 curves and show a minimum intensity when τ = 1/2J. In the APT case the CH2 curve takes larger values than the CH4 curve except at τ = 0, 1/2J and 1/J values where they have the same intensity. In the DEPT experiment, the maximum polarization transfer for CH4 takes place at τ = 1/6J and 5/6J, while for CH2 this happen at τ = 1/4J and 3/4J. This fact could be useful to distinguish the CH2 and CH4 signals using APT and DEPT experiments.