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Hetero‐“Tickling” am A 3 X ‐System von 13 CH 3 12 CN, eine Bestimmungsmethode hoher Genauigkeit von Methylkohlenstoffverschiebungen
Author(s) -
Wehrli F. W.,
Simon W.
Publication year - 1970
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19700530708
Subject(s) - chemistry , spectral line , heteronuclear molecule , degenerate energy levels , resonance (particle physics) , proton , atomic physics , spin (aerodynamics) , perturbation (astronomy) , nuclear magnetic resonance , physics , nuclear magnetic resonance spectroscopy , stereochemistry , nuclear physics , quantum mechanics , thermodynamics
Heteronuclear spin tickling experiments in the degenerate A 3 X spin system of a 13 CH 3 group have proved to be suitable for accurate carbon shift determinations in methyl groups. A weak perturbation of one of the 13 C quadruplet lines splits both proton doublet lines into a sub‐triplet with the relative signal strengths depending on whether an outer or inner 13 C line is irradiated. Deviation from exact resonance with one of the 13 C transitions modifies the relative intensities, and finally further splitting of the outer subtriplet lines occurs in accordance with theory. The amount of this additional splitting is equal to the difference between the double resonance frequency and the 13 C transition frequency to be measured. Signal distortions observed when the double resonance spectra are recorded in the INDOR sweep mode have to be ascribed to the fact that the tickling effect competes with the generation of transient nutations.