We explore herein the interconnection between the collective intermolecular solvent modes(CIM) and ultrafast reaction rate, assuming that frequency-dependent solvent friction controls the rate of suchreactions. We attempt to find a possible explanation for the observed near-insensitivity of ultrafast reactionrates (for example, charge transfer reaction) to the medium viscosity. Results are presented here by employingan analytical scheme that estimates the high-frequency solvent frictional response. Representative roomtemperature reaction media considered here are an ionic liquid (BMIMPF₆, η~310cP), a dipolar solvent(ethanol, η~1:09cP) and a deep eutectic solvent (Acetamide+ LiBr, η~1950cP). It is found that the wavenumber and frequency-dependent rotational friction, Г_R(ƙ,ᴢ), estimated by using the available experimental dielectric relaxation (DR) data for the ionic liquid and the deep eutectic solvent (DES), cannot predictthe viscosity independence of Г_R(ƙ,ᴢ) at high frequency. Missing dispersion in the DR data of the DES appears to be critical and incorporation of this missing amplitude via collective solvent intermolecular modescentered around 100 cm^-1 markedly improves the high-frequency behaviour of Г_R(ƙ,ᴢ): Subsequently, thecalculated Г_R(ƙ,ᴢ) for these solvents at high frequency exhibits near-insensitivity to medium viscosity andexplain the viscosity independence of ultrafast reaction rates.