The 2D Selective Heteronuclear J-Resolved experiment is the selective version of the spin-flip experiment. It allows to measure accurate long-range proton-carbon coupling constants directly from the F1 columns of a heteronuclear J-resolved spectrum.

Easy implementation on any AVANCE spectrometer.

The basic pulse sequence is easily derived from the SPIN-FLIP experiment. The only difference is that the 180º 1H pulse simultaneously applied to the 180º 13C pulse is made selective for an specific proton resonance ( 82JACS1099 ).


In this way, all 13C chemical shift and heteronuclear couplings except those of the inverted proton are refocus at the end of the evolution period.

Other alternatives are:

• Gated-decoupler method, in which selective irradiation during the half of evolution time replace the selective 180 pulse ( 84TL337 ).
• Replacement of the initial 90 carbon pulse by a DEPT ( 89JMR137-85 ) or a refocused INEPT ( 92MRC823 ) pulse train, in order to achieve a better sensitivity for protonated sites
• Simultaneous observation from two protons by applying two consecutive 180 proton pulses on two different sites ( 89JMR137-85 ). To measure proton-carbon coupling constants on non-protonated carbons, a selective 2D J-INEPT or selective 2D J-DEPT experiment are more advisable.

 Some applications have been described: 85JCS220 , 94MRC657 , and 95MRC196 .

The 2D Heteronuclear J-Resolved experiment can be recorded in routine/automation modes. The parameters to be consider are the offset and the selectivity of the selective inversion proton pulse. The relaxation period must be enough long to relax all carbon nuclei.

Tutorials: 2D X-detected experiments

The main advantage of selective 2D J experiments is the simple spectral analysis. It displays a typical proton-decoupled 13C spectrum in the F2 dimension. Each 13C resonance is splitted as a function of the number of selected protons. Thus, for instance, a quadruplet centered to F1=0 (+3J/2, +J/2, -J/2, -3J/2) is observed for each carbon resonance if a methyl group has been selectively inverted, a triplet (+J, 0, -J) if a methylene has been inverted, an a doublet (+J/2 and -J/2) if a single proton has been inverted. Non coupled and unresolved carbons appear as a singlets at F1=0. The observed splitting directly affords the long-range proton-carbon coupling constant value. Because the F1 dimension can be set to a minimum value, the resolution of this measurement can be about 0.2-0.3 Hz.

Related experiments:

2D X-detected experiments