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.

Key Words:

• NMR
• APT
• DEPT
• methane