1H Homonuclear Decoupling

The traditional homonuclear decoupling experiment is done with weak, selective decoupling (homonuclear decoupling) of one or a group of protons. Observation of the collapse of 1H fine splitting enables identification of through-bond coupled protons. This is an easy and quick experiment if only a few coupled partners are studied. Each coupling is studied separately with an on-resonance decoupling of one partner or separately both partners for the sake of symmetry, reducing its efficiency if many such couplings are examined. A majority of such studies can be done nowdays with 2D COSY-type experiments (such as gcosy) which allow simultaneous observation of all through-bond couplings in less time. However, a unique adavantage of this experiemnt is to offer clarity to a crowed 1H spectrum with complicated J-coupling splittings at a high resolution, or to quickly confirm a few well-guessed couplings.

To perform the homonuclear decoupling experiment (homodec sequence on the Varian systems), the user should pay attention to the following:

The 2D COSY experiment (gcosy) does not have any of the issues mentioned above. Linewidth, however, in gcosy is usually broader because of the use of short acquisition time and the absolute-value mode, but it is mostly sufficient and the peaks can be sharper if needed with longer at.


Pulse sequence and example reference (1st) and 3 selective decoupling offset frequencies (dof).

homodec setup

Procedure (on nmr500)

Step 1: Preparation

Step 2: Collect 1H spectrum

Step 3: Set up array for decoupling frequency offset (dof)

Step 4: Set nt and submit experiment

Step 5: Processing

For manual processing:

Default Parameters


Sample: Strychnine at ~ 25mg/mL (~ 100mM) in cdcl3
  • Data collected November 2010 (~ 4 mins with nt=8)

gcosy spectrum (20 mins)


Homodec Spectra (compare with gcosy spectrum above)


  • The bottom spectrum is the reference with decoupling at 5ppm. The red arrows indicate decoupling at peak positions of ~5.9ppm, 3.7ppm, and 2.35ppm from bottom to top. The green arrows indicate the collapse of J-coupled partner peaks into decoupled peaks.
  • A glitch peak (often out of phase) at the decoupling position (red arrow) often appears in the spectrum.

H. Zhou updated Nov 2010