Long Range 13C Couplings in Hexamethylphosphoramide and Dimethylsulphoxide

One bond ¹³C–¹H couplings have been extensively studied and their magnitudes explained on the basis of two contributing factors, namely the percentage “s” character of the bond¹ and the carbon Z value, or effective nuclear charge². To date however, little has been reported on ¹³C couplings over more than one bond, the main reason being the previous experimental difficulties in measuring these small couplings.