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Characterization of di‐ and trimethoxybenzaldehydes by analysis of deshielding gradients obtained with Eu(fod) 3 shift reagent
Author(s) -
Neville G. A.
Publication year - 1972
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.1270040505
Subject(s) - reagent , chemistry , proton , substituent , substrate (aquarium) , molar ratio , characterization (materials science) , stereochemistry , catalysis , nanotechnology , organic chemistry , materials science , physics , oceanography , quantum mechanics , geology
Eu(fod) 3 shift reagent was used to simplify PMR spectra from isomeric mono‐, di and trimethoxybenzaldehydes. Deshielding gradients, obtained by plotting induced shift vs . molar ratio of [Eu(fod) 3 ]/[substrate] made it possible to assign methoxyl proton signals to the correct positional substituent in polymethoxylated benzaldehydes. Anomalous upfield shifts for the aldehydic protons of 2,6‐dimethoxy‐ and 2,4,6‐trimethoxybenzaldehyde were observed with Eu(fod) 3 Various instances of long‐range ( 5 J ) proton coupling between the aldehydic proton and a meta ‐proton provide insight to the geometry of the substrate in the complexed state with Eu(fod) 3 . Di‐ and trimethoxybenzaldehydes are important precursors for the synthesis of the correspondingly methoxylated amphetamines which are of pharmacological and forensic interest because of abuse and illicit manufacture.