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Well chemistry before the discovery of quantum world was saying:"In order for a chemical reaction to happen , reactants must have enough energy to be converted into products."I was wondering now that we have discovered quantum worlds and quantum properties and quantum effects and quantum tunneling , maybe if the energy barrier is very narrow then we dont have to add this "Activation energy" and the reactants pass through this energy barrier to create products .

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  • $\begingroup$ Cant the reactants tunnel through the energy barrier to form products? $\endgroup$ – Donald Duck May 1 '19 at 15:25
  • $\begingroup$ Quantum tunneling can have a stunning effect on the rate of reactions, see for instance the example (science.sciencemag.org/content/299/5608/867) of work by Zuev et al. or the perspective by R. McMahon (science.sciencemag.org/content/299/5608/833). $\endgroup$ – Buck Thorn May 1 '19 at 15:38
  • $\begingroup$ Can this be done to all reactions? $\endgroup$ – Donald Duck May 1 '19 at 16:16
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    $\begingroup$ Please modify your question by clicking on the "edit" button in addition to seeking clarification here. Or, post this as a new question ("how important is tunneling as a reaction mechanism" or similar, although this might get shot down as too broad or requiring further research on your part). For the record tunneling can be important for any reaction where there is a proton or electron transfer involved and the electron/proton donor/acceptor are placed in a "sweet spot" that increases the importance of this over other mechanisms. $\endgroup$ – Buck Thorn May 1 '19 at 16:49
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Tunneling can be important for any reaction where there is a proton or electron transfer involved and the electron/proton donor/acceptor are placed in a "sweet spot" that increases the importance of this over other mechanisms.

As explained here, the conditions for appreciable contribution of tunneling to a reaction mechanism are that (1) the activation barrier be large enough (otherwise tunneling is not necessary); (2) the width of the barrier (the tunneling distance) should not be too great and (3) the particle must have significant wave (delocalized) character, that is, small mass (such as a proton or electron).

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  • $\begingroup$ In complement to this I would like to point out that Science magazine has editted and published a special disussing the tunneling of heavy elements which can be found here: science.sciencemag.org/content/299/5608/833. Now, it is hidden behind a paywall but it shows that tunneling in chemical reactions is a thing. Plus, in the public synopsis in that link the editor explains that the tunneling of electrons and hydrogens is important for many reactions, even some enzymatically catalyzed reactions. $\endgroup$ – urquiza May 11 '19 at 18:44

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