Premium
Dependence of vicinal 31 P– 31 P and 31 P– 13 C coupling constants on the dihedral angle of α, β‐diphosphonates
Author(s) -
Grossmann G.,
Lang R.,
Ohms G.,
Scheller D.
Publication year - 1990
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260280606
Subject(s) - chemistry , dihedral angle , coupling constant , vicinal , cyclohexane , nmr spectra database , spectral line , crystallography , diphosphonates , stereochemistry , analytical chemistry (journal) , molecule , organic chemistry , hydrogen bond , physics , bone resorption , particle physics , astronomy , biology , genetics
Several α,β‐diphosphonates with a norbornane or cyclohexane skeleton were prepared, and the 31 P‐ 31 P coupling constants over three bonds for the ethyl or methyl esters, the acid and anion were obtained from the 13 C NMR spectra or the 13 C satellites in the 31 P NMR spectra. The 3 J (PP) values cover a range of about 90 Hz and are therefore well suited for conformational and configurational analysis. The dependence of 3 J (PP) on the dihedral angle is well reflected by an extended Karplus relationship: 3 J(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 3 J (PC) on the PCCC dihedral angle show that a good curve fitting is achieved using the Karplus relationship 3 J (PC) = A A + 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 3 J (PC) values obtained for esters are similar for acids and anions.