NMR study of antipyrine adducts with lanthanide shift reagents. Molecular structure of 2,3-dimethyl -1-phenyl- 5-ethoxypyrazole

The complex formation of antipyrine with LSR in CCl4 is studied. Recommendations for producing the limiting lanthanide induced shifts characteristic of the 1∶1 complex are given and the geometry of the complex formed is determined. Results of an x-ray structure study of the adduct which is formed upon reaction of antipyrine and the ethyl ester of benzenesulfonic acid are presented.