An improved decoupled model has recently been proposed by us to account for the correlated internal rotations in flexible alkyl(oxy) chains of liquid crystals. In this model, the three-bond motions in the chain are disallowed, while both gauche migration and gauche pair production can now occur in the chain. Preliminary results from the analysis of deuteron spin relaxation rates in the liquid crystal 4-n-hexyloxy-4'-cyanobiphenyl (6OCB) were encouraging. We apply this motional model to interpret the existing relaxation data of 4-n-octyloxy-4'-cyanobiphenyl and 6OCB. Transition rates for the chain dynamics are obtained for both liquid crystals in conjunction with their overall rotational diffusion constants. The derived rotational diffusion constants are compared with those obtained from dielectric relaxation studies. A consistent picture emerges in the present study for the two members of a homologous series when the order director fluctuations are included in the nematic phases of these liquid crystals. (C) 2001 American Institute of Physics.