ISSN:
0749-1581
Keywords:
NMR
;
NMR Isotope effects on 13C chemical shifts
;
Deuterium isotope effects
;
18O isotope effects
;
Intramolecular hydrogen bonding
;
Steric strair
;
Hydrogen bond strength
;
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
A series of sterically hindered o-hydroxy aromatic ketones were synthesized, including benzene, naphthalene, phenanthrene and pyrene derivatives. Deuterium isotope effects on the 13C chemical shifts of 2-hydroxy-1-acenaphthone and other sterically hindered, intramolcularly hydrogen-bonded aromatic ketones (OH exchanged) are shown to be unusual. The two-bond isotope effects are very large. Likewise are the istope effects on C=O, C—1, C—3 and C—4 carbon resonances and some show unusual signs. These unusual effects are explained by a higher degree of twist in the deuterio than the protio compound. Steric isotope effects are also observed on OH chemical shifts of sterically hindered o-hydroxy acetyl aromatic compounds deuteriated at the methyl group. These isotope effects show non-additivity. For one-bond isotope effects, 1Δ13C(18O), hydrogen bonding leads to a decrease, whereas twisting of the carbonyl group leads to an increase. Two hydrogen bonds to the same acceptor has a reduced cumulative effect. Data for sterically hindered, hydrogen-bonded compounds are found to fall outside the correlation between δ(17O) and 1Δ13C(18O).
Additional Material:
9 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/mrc.1260320705
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