The reactions of O(D-1) atom with saturated hydrocarbons (RH), CH4, C2H6, and C3H8, were studied by monitoring the laser induced fluorescence of products OH in the nu " = 0 and 1 levels under bulk conditions and in van der Waals complexes, N2O . RH. O(D-1) was produced by the ArF excimer laser photolysis of N2O, Nascent rotational distributions are bimodal in all cases; the low-and high-N components. The former is formed from a long-lived collision complex generated by the insertion process. The collision complex has enough lifetime to randomize excess energy before decomposition. The high-hr component is produced in the short-lived insertion process, in which the collision energy of O(D-1) atoms is reflected in the rotational energy. The spin-orbit state in the only half-reactions producing the nu " = 0 level shows large population in the low-lying (2) Pi(3/2) State in low-N components, though spin-orbit populations are statistical in other reaction systems studied. The reaction proceeds via a transfer from a singlet reaction surface to a triplet surface keeping the conservation of the electronic angular momentum.