Deuterium fluoride gets born shivering Modern spectroscopic techniques can analyze collisions between gas phase molecules in exquisite detail, highlighting exactly which vibrations and rotations come into play. However, much chemistry of interest takes place in solution, where it's harder to tease out what happens. Dunning et al. applied infrared spectroscopy to study solution-phase formation of deuterium fluoride (DF) from F atoms, a longstanding test bed of gas phase dynamics. The DF product vibrated for a surprisingly long time before dissipating its energy to the surrounding solvent molecules. Science , this issue p. 530

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General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms Abstract:Reactions between Cl atoms and propene can lead to HCl formation either by direct H abstraction or through a chloropropyl addition complex. Barring stabilizing collisions, the chloropropyl radical will either decompose to reactants or form HCl and allyl products.

We report a theoretical investigation of the CH4 + Cl hydrogen abstraction reaction in the framework of empirical valence bond (EVB) theory. The main purpose of this study is to benchmark the EVB method against previous experimental and theoretical work. Analytical potential energy surfaces for the reaction have been developed on which quasi-classical trajectory calculations were carried out.The surfaces agree well with ab initio calculations at stationary points along the reaction path and dynamically relevant regions outside the reaction path. The analysis of dynamical data obtained using the EVB method, such as vibrational, rotational and angular distribution functions, shows that this method compares well to both experimental measurements and higher-level theoretical calculations, with the additional benefit of low computational cost.

Transient absorption spectroscopy is used to follow the reactive intermediates involved in the first steps in the photochemistry initiated by ultraviolet (266-nm wavelength) excitation of solutions of 1,5-hexadiene, isoprene and 2,3-dimethylbut-2-ene in carbon tetrachloride or chloroform. Ultraviolet and visible bands centred close to 330 nm and 500 nm in both solvents are assigned respectively to a charge transfer band of Cl-solvent complexes, and the strong absorption band of a higher energy isomeric form of the solvent molecules (iso-CCl3-Cl or iso-CHCl2-Cl). These assignments are supported by calculations of electronic excitation energies. The isomeric forms have significant contributions to their structures from charge-separated resonance forms, and offer a re-interpretation of previous assignments of the carriers of the visible bands that were based on pulsed radiolysis experiments. Kinetic analysis demonstrates that the isomeric forms are produced via the Cl-solvent complexes.Addition of the unsaturated hydrocarbons provides a reactive loss channel for the Cl-solvent complexes, and reaction radii and bimolecular rate coefficients are derived from analysis using a Smoluchowski theory model. For reactions of Cl with 1,5-hexadiene, isoprene and 2,3-dimethylbut-2-ene in CCl4, rate coefficients at 294 K are, respectively, (8.6  0.8)  10 9 M -1 s -1 , (9.5  1.6)  10 9 M -1 s -1 and (1.7  0.1)  10 10 M -1 s -1 . The larger reaction radius and rate coefficient for 2,3-dimethylbut-2-ene are interpreted as evidence for an H-atom abstraction channel that competes effectively with the channel involving addition of a Cl atom to a C=C bond. However, the addition mechanism appears to dominate the reactions of 1,5-hexadiene and isoprene. Two-photon excited CCl4 or CHCl3 can also ionize the diene or alkene solute.