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Aza crown ethers. 13 C and 1 H NMR studies of ring conformations and stereochemically dependent shifts in N ‐substituted dibenzodiaza‐18‐crown‐6 ethers and a nine‐membered analog
Author(s) -
Buchanan G. W.,
Landry D. J.
Publication year - 1991
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.1260290206
Subject(s) - chemistry , chemical shift , ring (chemistry) , crystallography , carbon 13 nmr , spin–lattice relaxation , stereochemistry , relaxation (psychology) , nuclear magnetic resonance spectroscopy , nuclear magnetic resonance , organic chemistry , psychology , social psychology , physics , nuclear quadrupole resonance
Abstract Remarkably large (> 10 ppm) 13 C NMR chemical shift differences are observed in solution and in the solid phase between ortho aromatic carbons of structurally analogous dibenzodiaza‐18‐crown‐6 ethers and their 9‐membered ring counterparts. On the basis of geometries deduced from 1 H 1 H NOESY results, the upfield 13 C chemical shifts in the 18‐membered systems are attributed to cis coplanar interactions between the terminal carbons of these torsional networks. Overall mobilities of 9‐ and 18‐membered ring systems are examined via 13 C spin–lattice relaxation times.