Journal of Physical Chemistry, Vol.98, No.20, 5207-5211, 1994
Variable-Field Study of C-13,Cl-35,Cl-37 Residual Dipolar Coupling in the C-13 CPMAS NMR-Spectra of Pyrazole Derivatives
High-resolution solid-state C-13 NMR spectra of the chlorinated derivatives 3,5-dimethyl-4-chloropyrazole, 4-chloro-5-methylpyrazole, and 3,5-bis(4’-chloropyrazol-1-yl)-4-chloropyrazole were recorded at 100.6 MHz (B-0 = 9.4 T) and at 50.3 MHz(B-0 = 4.7 T). The signals of the carbons bonded to chlorine appear as doublets at 9.4 T and as broad triplets at 4.7 T, due to incompletely averaged C-13,(35),Cl-37 dipolar coupling. The line shapes can be successfully simulated assuming typical values for the C-Cl bond distance and Cl-35 quadrupole coupling constant (including its sign).
Keywords:SOLID-STATE NMR;ANGLE-SPINNING SPECTRA;NUCLEAR MAGNETIC-RESONANCE;STRUCTURAL INFORMATION;QUADRUPOLAR NUCLEI;SPIN-1/2 NUCLEI;COMPLEXES;DEUTERIUM;CONSTANTS;HALIDES