Using Room-Temperature Water Microdroplets to Achieve C-H Activation

Bulk water is regarded as a benign substance, an excellent solvent of polar and ionic compounds, and relatively inert. In sharp contrast, tiny water droplets on the order of 20 microns or less in diameter (microdroplets) are highly reactive, can accelerate the rates of bulk water reactions by huge factors, and can even produce new compounds not found in bulk water. An example of the latter is the production of hydrogen peroxide (HOOH) at the surface of water microdroplets, arising from the recombination of hydroxyl radicals (•OH). Many doubt the truth of such reports or believe that HOOH is exclusively caused by ozone (O3) interacting with water.  This lecture will begin by providing a live demonstration of the partial conversion of water to hydrogen peroxide.

This past summer I had the good fortune of having Prof. Elumalai Gnanamani, IIT Roorkee, as a laboratory visitor, where he joined Dr. Yifan Meng in my research group to exploit HOOH production to cause C-H activation leading to C-N bond formation. In the brief time we have together, I want to describe only one such example, namely, the formation of anilines from aryl acids as well as both ammonia and primary/secondary amines via decarboxylation. It remains to be demonstrated whether this chemical transformation can be carried out on a preparative scale, but the power of water microdroplets to cause new chemical transformations is certainly evident from this work.