Work in progress (4) Combining measurements, SAR and theoretical calculations to predict k 298 for more species. INTRODUCTION • Gas-phase electrophilic addition of OH represents the primary sink for alkenes in the atmosphere, where the degree and type of substitution strongly affects their chemical reactivity. • This leads to a diversity of behavior that has presented a challenge for structure-activity relationships (SARs). • Here, we investigate and extend the potential of existing SARs to estimate temperature-dependent OH rate coefficients, k(T), of a large range of alkenes under atmospheric conditions. METHODOLOGY 1. We considered two different techniques: the group-additivity approach of Atkinson and co-workers [1] ; and the recent method of Tokuhashi and co-workers [2] to estimate k 298. 2. The latter was found to make superior predictions for halogenated olefins. This SAR was extended to include more species, and to predict temperature dependences. MAIN OBJECTIVE Build a hybrid easy-to-use screening tool, usable with or without experimental data, for assessing the environmental impact of these compounds before they reach the mass-production phase. (1) Experimental data [4] (2) Structure-activity relationship (SAR)