LONG-RANGE C-13-H-1 COUPLING-CONSTANTS IN 3-CARENE AND ALPHA-PINENE

Long-range C-13-H-1 coupling constants exceeding 0.3 Hz were measured for the hydrocarbons 3-carene and alpha-pinene by a heteronuclear 2D J-resolved proton-flip experiment with selective proton excitation. The dependences of the vicinal 3J(C, H) coupling constants on the dihedral angles were studied, and the peculiarities of the couplings through the double bond and cyclopropane framework were demonstrated. The dependences of the 4J(C, H) coupling constants in the allylic fragments of the molecular framework are discussed, and the long-range (n)J(C, H) coupling constants with the olefinic protons in camphene were investigated for the same purpose.