Up until relatively recently, experimental measurements of the rotational dynamics of small molecules in liquids were largely confined to seeing the effects of rotational diffusion. The molecular character of the process seemed of little relevance. However, newer measurements have begun to look in some detail at the microscopics behind molecular reorientation. We show in this paper that it is possible to understand the short-time dynamics of rotation in liquids at a molecular level by looking at the instantaneous normal modes of the remaining degrees of freedom. With the aid of some other, properly short-time, approximations, the reorientational dynamics can be cast into the form of an instantaneous generalized Langevin equation-one defined for each liquid configuration. One therefore obtains fully molecular expressions for the instantaneous rotational friction and fluctuating torque felt by a solute. The average friction so obtained seems to describe the basic nondiffusional aspects of rotation reasonably accurately and lends itself-as we illustrate in the companion paper-to more detailed investigations into the actual molecular mechanisms behind rotational relaxation. In the course of this work we also show that just as the autocorrelation function for the force on a rigid bond yields an accurate portrayal of the friction needed to study vibrational relaxation, quantitatively accurate results for the rotational friction can be provided by using molecular dynamics to compute the torque autocorrelation function for an orientationally rigid solute.