HCSE method for detection of small carbon–carbon couplings and their signs, comparison with SLAP pulse sequence

Abstract

Performance of homonuclear coupling sign edited (HCSE) experiment applied to detection of signed carbon-carbon couplings is discussed using a set of already measured samples of nine monosubstituted benzenes. It is shown that coupling sign detection is insensitive to the settings of carbon-carbon polarization transfer delays. The HCSE spectra of ten from the total of 43 measured carbon-carbon couplings were considerably influenced by relaxations and proton-proton strong couplings. These effects are quantitatively discussed. The results of HCSE and SLAP experiments are compared. It is shown that the two methods may complement each other in detection of signed carbon-carbon couplings.

NMR artifacts caused by decoupling of multiple-spin coherences: improved SLAP experiment

“…introduced another complete SLAP/COSLAP phase cycle of 256 or 512 scans and DQ‐filtered SLAP with complete phase cycle of 512 steps. In our experience, the parent signal suppression even by full SLAP phase cycles without DQ filter was unsatisfactory. Our DQ‐filtered SLAP offered very good parent signal suppression but at the expense of decreased signal intensity when compared with standard SLAP results in particular cases.…”

“…In our experience, the parent signal suppression even by full SLAP phase cycles without DQ filter was unsatisfactory. Our DQ‐filtered SLAP offered very good parent signal suppression but at the expense of decreased signal intensity when compared with standard SLAP results in particular cases. (Note on nomenclature: Because the paper deals with 13 C satellites in 13 C NMR spectra that originate in the isotopomers with two 13 C nuclei in the molecule, isotopomers with only one 13 C nucleus in the molecule are considered abundant and their proton decoupled 13 C NMR lines are termed parent or centerband lines in this text.…”