Structure and Reactivity of Transient Carbenes

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The Chemical Structure, Dynamics, and Mechanisms B Program supports Professor Robert A. Moss of Rutgers University to investigate the structure and reactivity of transient carbenes. The scientific objective of this work is to engage in mechanistic characterization of reactive intermediates, especially the chemistry of carbenes and carbanions. Its unifying theme is the correlation of structure with reactivity for highly reactive, short-lived intermediates. Activation parameters will be determined for carbene-alkene additions of the highly reactive carbenes Cl-C-CN, F-C-CN, Cl-C-CF3, and F-C-CF3. The results will bear upon the operation of enthalpy/entropy compensation in carbene/alkene addition reactions. Equilibrium constants and thermodynamic parameters will be measured for [PhCX + Y- = PhCXY-], where X,Y = F, Cl, and Br. Transient complexes of alkylchlorocarbenes with aromatic partners will be spectroscopically and computationally characterized. Modulation of carbenic reactivity by complexation will be probed. The chemistry of F-C-OPh encapsulated in a water-compatible hemicarcerand will be explored. Finally, the "umpolung" or philicity alteration of nucleophilic and ambiphilic carbenes by reaction with lithium salts will be studied.Carbenes are very unusual carbon-based molecules that are extremely reactive, living only billionths of a second in solution at room temperature. Carbenes can exist in different geometries with different arrangements of their outer electrons and this can lead to different reactivities. In this research project, a detailed set of fast spectroscopic measurements is made to determine the relationship between the geometry changes and the reactivity of these interesting molecules. Professor Moss is the Chair of the Coordinating Committee of the International Symposium on Reactive Intermediates and Unusual Molecules (ISRIUM), meeting in Mexico in 2014.