Premium
Carbon‐13 NMR studies of twenty‐four methyl‐substituted morpholines
Author(s) -
Nilsson Bertil,
Hernestam Sven
Publication year - 1978
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/mrc.1270110303
Subject(s) - steric effects , chemistry , ring (chemistry) , carbon 13 nmr , proton nmr , carbon fibers , chemical shift , spectral line , proton , stereochemistry , crystallography , computational chemistry , organic chemistry , materials science , composite number , physics , composite material , quantum mechanics , astronomy
Abstract Carbon‐13 NMR spectra of all the isomers of monomethyl‐, 2,3‐, 2,5‐, 2,6‐, 3,5‐dimethyl‐, 2,3,5‐, 2,3,6‐trimethyl‐ and 2,3,5,6‐tetramethylmorpholine have been obtained at both ambient (25 °C) and low temperature (∼ −100 to −120 °C). The ring carbon shifts appear to be additive with respect to the position of the methyl groups. A good correlation between predicted and experimental shift values was obtained ( r = 0.998 9 ). The values were used in an attempt to assign, conformationally, the ‘all cis ’ isomer 2,3,5,6‐tetramethylmorpholine, which from 1 HNMR spin–spin coupling studies has been unsuccessful. Methyl carbon shifts to high field were found for axially oriented carbons. The extracted ‘steric shift’ values for such carbons were compared to their corresponding proton shift data.