Texas Tech University
TTU HomeDepartment of Chemistry and Biochemistry Faculty Dr. David M. Birney

Dr. David M. Birney

Title:

Professor

Education:

Ph.D., Yale University, 1987; Postdoctoral Study, University of California, Los Angeles; Guest Professor, ETH - Zurich, Fall 2008

Research Area:

Physical Organic & Mechanistic Chemistry

Office:

Phone:

Fax:

Email:

Chemistry 232-C

806-834-7167

806-742-1289

David.Birney@ttu.edu

 

Research Group

Chem 2303 (2013)

Principal Research Interests

In our group, we use high level ab initio and density functional calculations to provide fundamental insights into two classes of reactions, pseudopericyclic and pericyclic. We then design and conduct experiments to test the predictions of these calculations. The synergy between theory and experiment has provided insights and research directions that would not be possible from either alone.

Pseudopericyclic Reactions

The "conventional wisdom" of the orbital symmetry rules tells an organic chemist what to expect from a pericyclic reaction. Pseudopericyclic reactions violate all of these expectations of a pericyclic reaction, yet strictly speaking they are orbital symmetry allowed. The fundamental difference between the two is that in a pseudopericyclic reaction, there is not orbital overlap around the ring of breaking and forming bonds. This allows their transition states to have a planar geometry, and, often, very low activation barriers.The difference between a planar pseudopericyclic transition state and a non-planar pseudopericyclic one is illustrated in two animations of these reaction pathways. The dramatic differences in geometries between them are summarized below.

Familiar Pericyclic Reactions

 

Novel Pseudopericyclic Predictions

Cyclic orbital overlap

 

Disconnections in orbital overlap

Non-planar, non-least motion transition states

 

Planar (or nearly planar) transition states

Pericyclic reactions can be allowed or forbidden, depending on the number of electrons

 

All pseudopericyclic reactions are allowed; there are no anti-aromatic transition states

Concerted pericyclic reactions have lower barriers than stepwise alternatives. Barriers are due to enforced electron-electron repulsion

 

Pseudopericyclic reactions can have lower barriers than pericyclic alternative. There is no enforced electron-electron repulsion

Representative Publications