The role of intramolecular vibrational energy redistribution in conformational reactions has been a topic of continued interest since low barrier conformational reactions are examples of systems that are intrinsically non-statistical in nature. Nearly three decades ago, De Leon and Berne investigated the dynamics of a model isomerization system in great detail. Interestingly, this early study has bearings on a topic of current interest - the sampling of rare events. In this work we bring out this connection in terms of phase space structures known as reactive islands and thereby provide the anatomy of a rare event. En route, we obtain insights into the transition path sampling method for harvesting rare trajectories from a phase space perspective. We show that quantum dynamics is sensitive to the reactive islands, thereby answering a question raised by De Leon and Berne. Our classical-quantum correspondence studies raise the possibility of defining a quantum rare event. (C) 2015 Elsevier B.V. All rights reserved.