New insights into organic chemistry from forefront physical measurements

As science advances it inevitably breaks down barriers between disciplines. This development occurs for the simple reason that nature neither knows nor cares about the organisational schemes that humans invent, and so scientific investigations will eventually run up against the limitations imposed by disciplinary boundaries. In the case of chemistry, one of the most fruitful meetings between erstwhile separate disciplines is occurring at the interface of chemical physics and organic chemistry. This volume seeks to highlight some examples of the new insights that are possible from application of a variety of physical measurements to organic reactions. Broadly speaking, the articles in the volume use either vacuum ultraviolet (VUV) or infrared (IR) photons to probe the reactions under study, although even that division is not rigid, because some of the investigations use both.

In the articles by Craig Taatjes (DOI: 10.1039/c2cp40294g) and David Osborne (DOI: 10.1039/c2cp41200d) and their coworkers one sees the remarkable information that can be obtained by the use of the tunable VUV radiation now available from synchrotron sources, in combination with mass spectrometry. In the former paper, the classic Criegee mechanism for ozonolysis, which appears in almost any undergraduate organic chemistry text, is directly probed. The key intermediates are detected, and the rate constants for their reactions are determined. In the latter paper, an addition reaction to an alkene—again a classic reaction of organic chemistry—is studied in exquisite detail. The contribution by Susanne Ullrich and coworkers (DOI: 10.1039/c2cp40178a) reveals the power of combined femtosecond time-resolved photoelectron spectroscopy and photofragment detection, following VUV excitation, for studying excited-state dynamics.

In the infrared arena, John Toscano and coworkers (DOI: 10.1039/c2cp40327g) use nanosecond time-resolved IR to detect and study the chemistry of a nitrene, while Matthew Platz and colleagues (DOI:10.1039/c2cp40226b) extend the investigations of related intermediates into the picosecond regime. Andrew Orr-Ewing and coworkers (DOI: 10.1039/c2cp40158d) study the picosecond dynamics of hydrogen atom abstraction by the CN radical in solution by broadband IR, and reveal a level of detail for the mechanism and dynamics of the reaction that would have been unthinkable even a few years ago. Keisuke Tominaga and colleagues (DOI: 10.1039/c2cp40244k) probe one of the most important, and still least understood, aspects of organic chemistry, namely solute–solvent interactions, through the use of nonlinear IR spectroscopy, while Igor Rubtsov and coworkers (DOI: 10.1039/c2cp40187h) show how relaxation-assisted two-dimensional IR spectroscopy can give unique insights into energy flow in organic molecules.

Together, studies of the kind highlighted here do much more than give detailed information about known mechanisms. Often they show that previously unknown processes are important, and, overall, they help to change the way in which we think about reaction mechanisms. It is my hope that this volume will be read by organic chemists who can learn about new ways of probing the reactions of interest to them and by physical chemists or chemical physicists who can learn of outstanding chemical problems to which their techniques might be profitably applied.

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