Premium
Inverse‐detected two‐dimensional NMR experiments on a system undergoing chemical exchange near coalescence
Author(s) -
Robinson Valerie J.,
Bain Alex D.
Publication year - 1993
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260310914
Subject(s) - heteronuclear molecule , chemistry , intramolecular force , chemical shift , spectral line , inverse , proton , carbon fibers , coalescence (physics) , nuclear magnetic resonance , carbon 13 nmr , nuclear magnetic resonance spectroscopy , analytical chemistry (journal) , stereochemistry , organic chemistry , physics , geometry , mathematics , materials science , astronomy , astrobiology , composite number , composite material , quantum mechanics
In systems undergoing intermediate chemical exchange, observation of carbon NMR signals by standard onedimensional methods is often hampered by severe line broadening accompanied by reduced sensitivity. In contrast, the HMQC inverse‐detected heteronuclear chemical shift correlated experiment detects the 13 C satellites of the proton lines. If the proton exchange is fast, the width of the satellites is independent of the intramolecular carbon exchange, and hence the carbons are more efficiently detected. The carbon spectrum of 1‐ tert ‐butoxycarbonyl‐ N ‐ tert ‐butyloctahydro‐1 H ‐indole‐2‐carboxamide serves to demonstrate this phenomenon. Carbons severely broadened in the 1D experiment appear largely unaffected when detected in the HMQC experiment. A straightforward explanation for this observation is presented together with a preliminary discussion of the carbon (F 1 ) line widths in the HMQC spectra of exchanging systems.