CARBON-13 NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY .I. COUPLING CONSTANTS BETWEEN CARBON-13 AND PROTONS THROUGH 2 BONDS

Carbon-13 resonances for some simple organic compounds were observed under slow passage conditions at 15.085 MHz. The magnitudes of the observed two-bond coupling constants between carbon-13 and protons, 2JCH, are discussed in terms of substituants and hybridization. For the system H-C1-13C2, the absolute values of 2JCH seem to increase with increasing electronegativity of the substituents at C2 and with decreasing electro-negativity of the substituents at Ci. It is suggested that the changes of hybridization and substituents at C1 have more effect on the magnitude of 2JCH than those at C2. In the case of cis-dichloroethylene, the sign of 2JCH was determined to be the same as that of 1JCH.