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The 2D long-range optimized heteronuclear correlation experiment is a carbon-detected experiment that permits to obtain a 2D chemical-shift proton-carbon correlation map in which two- and three-bonds proton-carbon connectivites can be elucidated.REQUIREMENTS
Easy implementation on any AVANCE spectrometer.VERSIONS
The basic pulse sequence to record 2D long-range optimized HETCOR experiments is the same described in one-bond optimized 2D HETCOR experiment in which the delays are optimized to long-range coupling constant values ( 84JMR93-57 and 84TL6007 ). However, a major problem of this sequence is the presence of one-bond correlations and the modulations of long-range correlations by local one-bond couplings. A lot of modificated pulse sequences have been proposed which have been efficiently reviewed ( 88MRC652 ):EXPERIMENTAL DETAILSLong range optimized versions of the DEPT-based HETCOR experiment have been also reported ( 85JCS370 , 89MRC68 . and 93JMRA1-102 ).
- Replacing the last proton 90º pulse by a TANGO operator ( 86MRC1083 and 87JMR554-71 ).
- Inserting a BIRD operator in the D3 delay ( 87MRC752 , 88MRC367 , 89MRC123 , 88JHC693 , and 88MRC542 ).
- Combining low-pass J filter and BIRD operator ( 88MRC28 , 92JMR103-96 , and 88JMR280-80 ).
- Combining TANGO and BIRD operators ( 87JMR556-72 , 88MRC362 , and 88JMR333-78 ).
- Combining several BIRD operators (FLOCK experiment) ( 89MRC162 ).
- Using a INEPT-based scheme ( 89JMR69-85 ).
The 2D long-range HETCOR experiment can be recorded in routine/automation modes. Acquisition parameter set-up as described in 2D HETCOR experiment except the delays D2 and D3 that are optimized to nJ(CH) (5-10 Hz).SPECTRAMore details on practical implementation of 2D long-range optimized HETCOR experiments on AVANCE spectrometers can be found in
Tutorials: 2D X-detected experiments
A typical 2D map in which cross-peak stands for a two- or three-bond proton-carbon connectivity. Direct responses can also be present depending of the version used. In addition, long-range cross-peak intensity is dependent to the corresponding long-range coupling constant and therefore this is dependent to interpulse delay optimization.RELATED TOPICS
Presently, improved sensitivity ratios are obtained from heteronuclear correlation experiments based on proton detection as the HMBC experiment.Related experiments:
2D X-detected experiments
