Non-Statisticality, Selectivity and Phase Space Structure in Organic Reactions

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The proposed research is submitted under the NSF/EPSRC Chemistry Proposals 2011 call for proposals. Our US collaborator is Professor Gregory S. Ezra of the Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York. This work is a theoretical and computational exploration of nonstatistical dynamics in organic reactions, motivated by recent experiments, and its relation to phase space structure in classical Hamiltonian models for polyatomic molecules. The overall aim of the research is the development of a phase space approach to understanding and ultimately predicting nonstatistical dynamics in thermal reactions of organic molecules. Such reactions have been the focus of much recent experimental and theoretical work, which has convincingly demonstrated that, for a growing number of cases, standard transition state theory approaches for prediction of rates, product ratios, stereospecificity and isotope effects fail completely. The proposed research will apply the significant recent theoretical and computational advances in applied dynamical systems theory (e.g., normal form theory) to study reaction dynamics and phase space structure in multimode molecules, and to probe the dynamical origins of nonstatistical behavior. The gap time formalism for unimolecular rates will be used to provide novel diagnostics for nonstatistical behavior.These methods will be applied to a investigate a number of representative cases: branching ratios in systems exhibiting reaction path bifurcation; stereospecificity in nominally pericyclic reactions involving diradical intermediates; nonstatisticality and dynamic matching in reactions occuring on shallow potential walls. The influence of bath modes will be studied and, ultimately, the nature of quantum effects for such systems will be explored.Control of selectivity is arguably the most important problem that synthetic chemists face. Understanding the factors that control selectivity is of essential importance to the chemical enterprise, and the proposed work begins to develop the fundamental mathematical framework that will be necessary to make non-empirical reaction design a reality. It is anticipated that the work will provide a rigorous dynamical foundation for the ongoing paradigm shift in the interpretation of organic reaction mechanisms, and so have considerable impact beyond the field of theoretical chemistry.Annual exchanges of postdocs between collaborating institutions will ensure that the coworkers involved in the project will receive a broad interdisciplinary education in a wide range of research methodologies. There will in particular be fruitful cross-fertilization between the subfields of chemical dynamics, dynamical systems, and the study of organic reaction mechanisms, as required for a new generation of researchers in chemistry.This project is a unique collaborative effort spanning the fields of physical organic chemistry, theoretical reaction dynamics and applied dynamicalsystems theory. It addresses problems of reactivity and selectivity in organic reactions that are of immense practical and theoretical importance, while exploiting state-of-the-art methodology and concepts from the theory of Hamiltonian dynamics. The synergy provided by such a collaborative effort is essential for full progress to be made in understanding this important class of problems in reaction dynamics. The PIs bring a combination ofdifferent backgrounds and strengths whose application to the proposed problems in physical organic chemistry is, as far as we know, unprecedented. The complementary skills and expertise of the three PIs will form a well-balanced ``tripod'' of capabilities for attacking these problems.