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Science 26 January 2007:
Vol. 315. no. 5811, p. 433
DOI: 10.1126/science.315.5811.433d
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Figure 1 The role of water in many atmospheric reactions remains poorly understood at the molecular level because it is difficult to distinguish nonspecific effects, such as collisional activation, from direct participation of water as a catalyst. Vöhringer-Martinez et al. (p. 497; see the Perspective by Smith) combined precise kinetic measurements with quantum-chemical calculations to implicate a catalytic role for individual water molecules in the gas-phase reaction of OH radicals with acetaldehyde. Their results suggest that water complexation to acetaldehyde lowers the subsequent barrier to attack by OH. The increasing instability of such complexes with rising temperature accounts for an unusual negative dependence on temperature of the magnitude of the catalytic effect.

CREDIT: VÖHRINGER-MARTINEZ ET AL.




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