ISSN:
0749-1581
Keywords:
Diphosphonates
;
Vicinal P-P and P-C coupling constants
;
Karplus relationship
;
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Several α,β-diphosphonates with a norbornane or cyclohexane skeleton were prepared, and the 31P-31P coupling constants over three bonds for the ethyl or methyl esters, the acid and anion were obtained from the 13C NMR spectra or the 13C satellites in the 31P NMR spectra. The 3J(PP) values cover a range of about 90 Hz and are therefore well suited for conformational and configurational analysis. The dependence of 3J(PP) on the dihedral angle is well reflected by an extended Karplus relationship: 3J(PP) = A + B cos ϕ + C cos 2ϕ + D cos 3ϕ, with different parameters for the esters, acids and anions. For trans and gauche arrangements of the α,β-diphosphonic acids the dependence of the P-P coupling constants on the degree of titration is given. Investigations of the dependence of 3J(PC) on the PCCC dihedral angle show that a good curve fitting is achieved using the Karplus relationship 3J(PC) = AA + AB cos ϕ + C cos 2ϕ. A comparison of these curves with published data indicates smaller coupling constants for ϕ ≈ 0°. The coefficients of the Karplus equation for the 3J(PC) values obtained for esters are similar for acids and anions.
Additional Material:
1 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/mrc.1260280606
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