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An unexpected twist in one of the mechanistic stalwarts of organic chemistry, the bimolecular nucleophilic substation, or SN2, reaction has been observed in the gas phase. Researchers in Germany and the US have obtained direct evidence for this substitution mechanism in the reaction of chloride ion with methyl iodide. Surprisingly, however, their study also revealed a roundabout mechanism in which the collision of the chloride ion with the methyl group of the iodo-compound spins the molecule through a full rotation before the chloride switches places with the iodide. To some extent, the findings challenge one of the most cherished models of elementary organic reactions.