To understand the mechanism of energy dissipation of dilute polymer solutions at high frequencies, we carry out a Brownian dynamics study of a linear polymer chain where beads represent individual backbone atoms and bending and torsional potentials are imposed to realistically model an alkane chain. We observe the end-to-end vector autocorrelation function from our simulations is in excellent agreement with the theoretical Rouse model predictions. Nevertheless, the backbone bond vector autocorrelation function exhibits a much slower decay than is predicted by the coarse-grain Rouse theory except near the longest relaxation time. We find that both the bending and torsional potentials slow down the contributions of local relaxation modes which brings the relaxation of short chains closer to single-exponential behavior than to the Rouse spectrum. This result is in qualitative agreement with measurements of birefringence relaxation (Lodge, T. P.; Miller, J. W.; Schrag, J. L. J. Polym. Sci.: Polym. Phys. Ed. 1982, 20, 1409-1425) and the notion of a "dynamical Kuhn length" (Larson, R. G. Macromolecules 2004, 37, 5110-5114).