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Resonance-stabilized hydrocarbon-radical chain reactions may explain soot inception and growth

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Science  07 Sep 2018:
Vol. 361, Issue 6406, pp. 997-1000
DOI: 10.1126/science.aat3417

A radical route to soot

The chemical origin of soot is a persistent puzzle. It is clear that small hydrocarbon fragments formed in flames must aggregate into larger particles, but the initial driving force for aggregation remains a mystery. Johansson et al. combined theory and mass spectrometry to suggest a solution based on resonance-stabilized radicals (see the Perspective by Thomson and Mitra). Aromatics such as cyclopentadiene have a characteristically weak C–H bond because their cleavage produces radicals with extended spans of π-electron conjugation. Clusters thus build up through successive coupling reactions that extend conjugation in stabilized radicals of larger and larger size.

Science, this issue p. 997; see also p. 978

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