Abstract: A theoretical model for calculating the nuclear spinspin coupling constants of the directly-boned C-H and C-C bonds was formulated using the s-character of the hybrid orbitals and the atomic net charges as the variables. The model was applied to calculate ¹J_CX (X=C, H) of a number of hydrocarbons based on the maximum overlap symmetry molecular orbital (MOSMO) method under PM3 approximation and the maximum bond order hybrid orbital (MBOHO) procedure. The calculated values were found to be in good agreement with the experimental data, supporting the notion that the Fermi contact term are a dominant factor in determining the carbonhydrogen and carboncarbon spinspin coupling constants over one bond. The method developed provided a platform to interpret and calculate ¹J_CH and ¹J_CC based on simple valence bond theory.

Key words: nuclear spin-spin coupling constant, maximum overlap symmetry molecular orbital, PM3 approximation, maximum bond order hybrid orbital