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Carbon‐13 assignments in 1‐ and 2‐naphthyl compounds: Extensive benefits of deuterium substitution
Author(s) -
Kitching William,
Bullpitt Maxwell,
Doddrell David,
Adcock William
Publication year - 1974
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.1270060511
Subject(s) - deuterium , chemistry , kinetic isotope effect , substituent , carbon 13 , aryl , carbon fibers , spectral line , decoupling (probability) , proton , carbon atom , medicinal chemistry , computational chemistry , organic chemistry , atomic physics , materials science , physics , alkyl , nuclear physics , astronomy , control engineering , composite number , engineering , composite material
The natural abundance, proton‐decoupled carbon‐13 spectra of 1‐methylnaphthalene, 1‐fluoronaphthalene, l‐naphthonitrile and their 4‐deutero analogues, as well as 2‐naphthol and its 6‐deutero analogue, have been recorded. Careful comparisons of the spectra of the deuterated and undeuterated compounds allow assignment, not only of the deuterated carbon, but also of the two ortho carbons (based on an upfield ‘two‐bond’ deuterium isotope effect), as well as the two meta carbons (based on a significant J (CCC D ) of ∼1 Hz) which causes substantial broadening). In the 1‐naphthyl compounds, significant coupling between the deuterium (at C 4 ) and C 5 allows assignment of this latter carbon. Thus, the consequences of the introduction of one deuterium atom, together with results from off‐resonance noise decoupling, permits assignment of most of the spectra. Tentative, but very likely assignments of the few remaining signals, can be made on the bases of chemical shifts and compressional effects. This approach could allow indirect assignment of an aryl carbon to which direct attachment of deuterium is difficult, due to directive effects of an existing substituent.