Question

Discuss the physical origins of quantum mechanical tunnelling. Why is tunnelling more likely to contribute to the mechanisms of electron transfer and proton transfer processes than to mechanisms of group transfer reactions, such as AB + C → A + BC (where A, B, and C are large molecular groups)?

Answer 1

Answer:

physical origin of this effect as a consequence of the wave nature of matter and our probabilistic interpretation.

Explanation:

When we solve the Scrödinger equation in a system with potential barrier type, the wave functions we find for the electron with less energy than the height of the bar. The wave functions have an oscillatory form before reaching the barrier and a decaying exponential form within the barrier, if the barrier is narrow enough, the exponential not close to zero so that after the barrier the wave function has through an oscillatory form, of course the coefficients are different, the imposing condition that the functions and their first derivatives are continuous, we can have the case that the electron crosses the barrier this is the so-called tunnel effect.

We can physical origin of this effect as a consequence of the wave nature of matter and our probabilistic interpretation.

In the case of molecular AB + C A + BC

It is general for a chemical reaction that the bond of the molecular AB should be broken before it can react with the C molecule, but if the formation energy (enthalpy) of the AB molecule is high this breaking is very unlikely. Therefore, these reactions have very little efficiency.

With the tunnel effect, the atom C has a small probability of reaching the proximity of the atom B and forming the molecule BC, displacing the atom A, this implies that the formation energy of the molecule BC is lower so that the atom A would remain free.