Reactive spreading diffusion limited

Absolute rates for hydrogen abstraction form the stannane, the second propagation step, have also being measured.17 These are indeed exceedingly efficient processes. These rates are on the higher end of the scale with relatively little spread (Figure 4.2). Aromatic, vinylic and cyclopropyl radicals react fastest, at close to the diffusion limit, whereas aliphatic radicals are some 100 times slower, with not much difference between primary, secondary and tertiary systems. Benzylic radicals, on the other hand, are the least reactive. 

Mortensen, A. Drevet, B. Eustathopoulos, N. Kinetics of diffusion-limited spreading of sessile drops in reactive wetting. Scr. Met. 1997, 36 (6), 645-651. 

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