The 2D Heteronuclear J-Resolved experiment allows to separate the heteronuclear coupling constant and heteronucleus chemical shift informations in separate dimensions of a 2D spectrum. This experiment was the basis of the initial concept of heteronuclear 2D NMR spectroscopy but its actual use is very limited. Nowadays, heteronucleus multiplicity analysis and direct coupling constants measurements can be performed by most modern methodologies.

Easy implementation on any AVANCE spectrometer.

The basic experiment of the 2D heteronuclear J-resolved spectroscopy is the Spin-Flip experiment ( 76JMR291-24 , 77JMR133-26 , 77JMR373-26 , 77JMR511-27 , 77JMR383-25 , 77JMR17-28 , nd 80JMR200-41 ). During the relaxation delay, proton decoupling is applied to generate the corresponding NOE on the carbon nuclei. A 90º 13C pulse creates tranverse magnetization which evolves during the variable evolution period. Simultaneous 180º 1H and 13C pulses are applied at the middle of this period to refocus 13C chemical shift evolution while the heteronuclear coupling is not affected. Carbon acquisition is performed under broadband proton decoupling.

Several modifed sequences have been proposed:

• A simplified version allows J-modulation only during the half of the evolution period (gated-decoupler method) ( 76JMR839-65 , 76JMR291-24 , 77JMR133-26 , 77JMR373-26 , 77JMR383-25 , 77JMR17-28 , and 77JMR29-28 ). In this case, couplings are scaled dwn by a factor of 2.
• Use of a BIRD cluster to differentiate direct from long-range couplings ( 83JMR330-52 , 84JMR87-56 , 84JMR132-58 , and 86JMR100-69 ).
• Improved sensitivity by incorporating an INEPT ( 83JMR495-53 ) or DEPT ( 83JACS4095 ) pulse trains as an initial transfer step .
• For accurate measurements of long-range proton-carbon coupling constants see 2D selective J-resolved experiment.

The 2D Heteronuclear J-Resolved experiment can be recorded in routine/automation modes. Only the basic parameters need to be specified the first time the experiment is executed. The relaxation period must be enough long to relax all carbon nuclei.

Tutorials: 2D X-detected experiments

The 2D heteronuclear J-Resolved spectrum displays a typical proton-decoupled 13C spectrum in the F2 dimension. Each 13C resonance is splitted by the typical (n+1) multiplet in the F1 dimension by the 1J(CH) value. Thus, for instance, each methyl carbon will appear as a quadruplet centered to F1=0 (+3J/2, +J/2, -J/2, -3J/2), each methylene carbon as a triplet (+J, 0, -J), each methine carbon as a doublet (+J/2 and -J/2), and each non-protonated carbon as a singlet at F1=0

Related experiments:

2D X-detected experiments