Premium
17 O NMR study of p‐π conjugation in methoxybutadienes and related compounds
Author(s) -
Taskinen Esko
Publication year - 1995
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.1260330406
Subject(s) - diene , chemistry , substituent , benzene , stereochemistry , nmr spectra database , carbon 13 nmr , medicinal chemistry , spectral line , organic chemistry , natural rubber , physics , astronomy
The 17 O NMR spectra of some monomethoxy and dimethoxy derivatives of buta‐1,3‐diene, hexa‐2,4‐diene, cyclohexa‐1,3‐diene and cyclohexa‐1,4‐diene were recorded in CDCl 3 . The δ( 17 O) values show that in 2‐methoxybuta‐1,3‐diene the efficiency of p‐π conjugation in the OCC moeity is significantly lowered by cross‐conjugation of the CC bond with the other olefinic linkage. In the related system of 2‐methoxycyclohexa‐1,3‐diene, however, the corresponding effect is much smaller, apparently because of weak conjugative π‐π interaction in the olefinic system. On the other hand, the strength of p‐π conjugation appears to be the same in the OCCCC moieties of both 1‐methoxybuta‐1,3‐diene and 1‐methoxycyclohexa‐1,3‐diene. Moreover, as a transmitter of substituent effects, the unsaturated system of cyclohexa‐1,3‐diene is comparable to that of the benzene nucleus.