Application of carbon-13 nuclear magnetic resonance spectroscopy. 24. The spectra of cyclopropane-annelated bicyclo[2.2.2]octanes, three-membered-ring effects and chemical shift nonequivalence

1980 ◽  
Vol 45 (22) ◽  
pp. 4329-4333 ◽  
Author(s):  
Harald Guenther ◽  
Wolfgang Herrig ◽  
Horst Seel ◽  
Stefan Tobias ◽  
Armin De Meijere ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Magnetic Resonance Spectroscopy ◽  
Nuclear Magnetic Resonance Spectroscopy ◽  
Membered Ring ◽  
Resonance Spectroscopy ◽  
Nuclear Magnetic

The characterization of primary, secondary, and tertiary vanadate alkyl esters by 51V nuclear magnetic resonance spectroscopy

1988 ◽  
Vol 66 (10) ◽  
pp. 2570-2574 ◽  
Author(s):  
Alan S. Tracey ◽  
Michael J. Gresser
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Magnetic Resonance Spectroscopy ◽  
Nuclear Magnetic Resonance Spectroscopy ◽  
Chemical Shifts ◽  
Hydroxyl Group ◽  
Resonance Spectroscopy ◽  
Low Field ◽  
Nuclear Magnetic

A variety of alkyl vanadates has been studied by 51V nuclear magnetic resonance spectroscopy. It was found that the equilibrium constant for condensation of vanadate with alcohols is insensitive to whether the hydroxyl group is primary, secondary, or tertiary. These products, however, have characteristic vanadium chemical shifts that allow assignment of nmr signals to the appropriate ester. It was also found that chemical shifts are additive in the sense that the chemical shifts of the esters ROVO3H− are one half the chemical shift of the diesters (RO)2VO2− when those shifts are given relative to −559 ppm. This effect is independent of whether the signals are to high or low field of −559 ppm and the additivity extends to mixed ligand systems. This value of −559 ppm is close but not equal to the chemical shift of the vanadate monoanion, H2VO41−, which is at −561 ppm. These results are at variance with arguments concerning the effects of ligand bulkiness on chemical shifts of vanadium(V) complexes.

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