The dynamics of the ultraviolet (UV) photoexcitation of methyl nitrite in weakly interacting perfluoromethylcyclohexane solution are investigated using transient absorption spectroscopy. UV excitation in the structured S1 <- S0 absorption band induces dissociation, with geminate recombination and vibrational cooling of syn and anti-conformers of methyl nitrate on a timescale of similar to 56 ps. Solvent-induced vibrational cooling favours relaxation to the higher-energy anti-conformer on entropic grounds, and subsequent inter-conversion to the lower-energy syn-conformer is prevented by a 3500 cm(-1) barrier. UV excitation to the S-2 state produces a transient electronic absorption band resembling the absorption spectrum of NO2. (C) 2017 Elsevier B.V. All rights reserved.