Ambiguity with reaction equations I understand that if two particles are on the left hand side of a reaction equation they are said to "interact". For example, $p+e^{-}\rightarrow n+v_e$ is a proton and electron interacting (electron capture).
What about the right hand sides? Does $p+e^{-}\rightarrow n+v_e$ also imply that the neutron and electron neutrino are interacting? Is it correct to look at this equation and say "it shows a neutron and antineutrino interacting?"
I think the answer is that it is incorrect because they are the products of the interaction on the left hand side and no interaction has to happen between them, so it would be wrong to say they are interacting.
This brings me onto another question. We know that leptons only interact with other particles via the weak force. Now imagine an equation where the left hand side has no leptons, and the right hand side has leptons. Would it be correct to say that this interaction happened by the weak interaction (due to the leptons on the right hand side)? I think the answer to this is a no as well: It is incorrect because the stuff on the right hand side isn't interacting with each other.
Please answer both questions,
thanks!
 A: If certain reaction is allowed, the inverse reaction (if energy and momentum are conserved) will be allowed too. So neutrinos (not antineutrinos) can interact with neutrons to yield electrons and protons.
For your second question: leptons can interact via electromagnetism, too. Electrons and positrons are leptons, and they interact mediated by photons: Bhabha scattering, Møller scattering, annihilation,.... Equivalent weak processes exist, but they are very improbable.
 
The presence of leptons is not the only criterion to know if a reaction is weak: A reaction is only weak if 


*

*Parity conservation is violated (because both strong interactions and electromagnetism conserve parity)

*If you have leptons (no strong interaction) and some of the particles, other than photon, are neutral (Even if hadrons can be neutral, they're made of charged quarks) (no electromagnetism). This applies to both sides of the reaction.


Otherwise, weak processes are allowed, but strong/electromagnetic are the dominant ones.
A: I have to take issue with Demosthene's textual analysis in a comment on the question.
To examine the physics rather than the way chemists talk, we should look at a tree level Feynman diagram for the reactions. Any reaction. Both the reactants and the products touch the participate in a vertex with the force carrying boson, so both have an equal claim to be "interacting".
And while you can draw higer-order diagrams that divorce the products from the core boson, you can also draw diagrams that divorce the reactants.
So, short answer: yes, the products are interacting.
