Chemistry Reference
In-Depth Information
2.5.2 Vinyl Azides
2.5.3 Aryl Azides
2.6 Structure and Photochemistry of Hetero-Azides
2.6.1 Carbonyl Azides
2.6.2 Phosphyl Azides
2.6.3 Other Azides
2.7 Unanswered Questions and Calculations to be Performed
Acknowledgments
References
2.1
INTRODUCTION
Computational studies have played a critical role in understanding the reactivity and
character of nitrenes. Indeed, it is difficult to think of a field of chemistry in which
computation has been a more complementary partner with experiment than in the
study of reactive intermediates in general, and the study of nitrenes in particular.
Major developments in experimental techniques for studying nitrenes such as
transient laser spectroscopy have allowed researchers to study these fleeting inter-
mediates by direct rather than indirect means, marking a significant advance in the
study of these intermediates. Paralleling these developments in experimental meth-
odology have been advances in computer hardware and computational methods that
have likewise allowed the nature and reactivity of these important reactive inter-
mediates to be probed
in silico
with increasing sophistication. This concomitant
evolution of both experiment and theory has led to increasingly fruitful two-pronged
experimental/computational collaborations in the study of these important, but
fleeting species. As testament to this synergistic partnership, most new papers
published on nitrenes today contain both an experimental and computational
component.
Computational methods aid in the study of nitrenes in two ways: first, by helping
with the interpretation and characterization of experimental data; and, second, by
computing properties of nitrenes that are difficult or impossible to obtain exper-
imentally. Perhaps the most critical role that computational studies have played in
supporting experimental studies has been in computing the spectroscopic signatures
of nitrenes to validate assigning experimental spectroscopic signatures to specific
molecular structures. For instance, computed IR/Raman and UV-Vis bands can be
compared to experimental spectra. But computational studies have also helped
elucidate a number of properties of nitrenes that are difficult (or impossible) to
determine experimentally, such as the molecular geometries, electronic-state order-
ings, partial atomic charges, spin densities, precursor excited-state dynamics, and
energy barriers for competing decomposition channels. Indeed, it is no coincidence
that the understanding of nitrenes and related species has paralleled the maturation of
