The additivity of NMR carbon–carbon spin–spin coupling constants

Fluorene-9-¹³C, fluorenone-9-¹³C, acenaphthenone-11-¹³C, acenaphthenone-12-¹³C, 1-methylcyclopentanol-1-¹³C and 1-methylcyclopentene-1-¹³C were synthesized to obtain J(CC) values between the natural carbons and the labeled carbons. Each of these compounds possessed at least one asymmetric dual-path coupling, i.e., coupling between the labeled carbon and another carbon via simultaneous two- and three-bonded coupling paths. Model ¹³C-labeled compounds were synthesized where necessary to give expected values of the constituent mono-path couplings. Values of these dual-path couplings (²⁺³)J suggested that the observed value is the (at least approximate) algebraic sum of the two constituent J values.