Paul Kiprof, Associate Fellow

Silene Cycloaddition Reactions

  The reaction of silicon-carbon double bonds with other molecules that have multiple bonds was studied at high levels of theory using ab initio molecular orbital theory. Research focused on the reaction of silene with acetylene and ethylene; this reaction poses a challenge to the understanding of cycloaddition reactions. The corresponding reactions of ethylene with aretylene and ethylene are known to proceed photo-chemically, whereas the reactions involving silene can be carried out thermally in the dark. The transition state of the silene reactions in the concerted type of this reaction was studied. These researchers were concerned with the alternative stepwise pathways of the reaction, which involve stable inter-mediates.

Carbocations are reactive intermediates in organic chemistry. Studies of the effects that heteroatoms, particularly oxygen atoms, have on the stability and chemistry of carbocations were conducted by the researchers. Carbocations stabilized by oxygen atoms-carboxonium ions-can achieve stability under normal, preparative conditions are interesting for synthetic applications such as the Criegee rearrangement. The structure of a directly observed cage carboxonium ion was predicted, while the observed NMR signals of this intermediate in solution could be assigned using Density Functional theoretical methods. This highly symmetric cation is significantly stabilized through the interaction of two oxygen atoms.

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