Isoprene carries approximately half of the flux of non-methane volatile organic carbon emitted to the atmosphere by the biosphere. Accurate representation of its oxidation rate and products is essential for quantifying its influence on the abundance of the hydroxyl radical (OH), nitrogen oxide free radicals (NO ), ozone (O), and, via the formation of highly oxygenated compounds, aerosol. We present a review of recent laboratory and theoretical studies of the oxidation pathways of isoprene initiated by addition of OH, O, the nitrate radical (NO), and the chlorine atom. From this review, a recommendation for a nearly complete gas-phase oxidation mechanism of isoprene and its major products is developed. The mechanism is compiled with the aims of providing an accurate representation of the flow of carbon while allowing quantification of the impact of isoprene emissions on HO and NO free radical concentrations and of the yields of products known to be involved in condensed-phase processes. Finally, a simplified (reduced) mechanism is developed for use in chemical transport models that retains the essential chemistry required to accurately simulate isoprene oxidation under conditions where it occurs in the atmosphere-above forested regions remote from large NO emissions.

Redox chemistry during the activation of carbon dioxide involves changing the charge state in a CO molecular unit. However, such changes are usually not well described by integer formal charges, and one can think of COO functional units as being in intermediate oxidation states. In this article, we discuss the properties of CO and CO-based functional units in various charge states. Besides covering isolated CO and its ions, we describe the CO-based ionic species formate, oxalate, and carbonate. Finally, we provide an overview of CO-based functional groups and ligands in clusters and metal-organic complexes.

Supporting Information 1 Characterization of Instrument Effects using NO2 PhotolysisExperiments measuring the instrument response function (IRF) used a certified mix of NO2 in He (Matheson Tri-Gas, 1.00% NO2 with 0.5% O2 as a stabilizing agent in He). We conducted NO2 photolysis experiments at 8 Torr and 10.0 eV photon energy. The NO + and NO2 + signals are shown in Figure S1. Following photolysis at t = 0, we observed a small depletion in the NO2 + and a fast rise in the NO + signal. The measured depletion of NO2 (from both photolytic and kinetic reactions) was 4.6 ± 0.5% determined by fitting the data over the time range from −20 to 20 ms. At later 1

We explore the structures of [Ti(CO) ] cluster anions using infrared photodissociation spectroscopy and quantum chemistry calculations. The existence of spectral signatures of metal carbonyl CO stretching modes shows that insertion of titanium atoms into C-O bonds represents an important reaction during the formation of these clusters. In addition to carbonyl groups, the infrared spectra show that the titanium center is coordinated to oxalato, carbonato, and oxo ligands, which form along with the metal carbonyls. The presence of a metal oxalato ligand promotes C-O bond insertion in these systems. These results highlight the affinity of titanium for C-O bond insertion processes.