The Attempt at a Solution
I thought the answer should be this:
But in the answer key, its something else. In the answer key, it is:
I don't understand why the left ring doesn't react.
Okay, i get it, you mean that the electron would stay in the right ring most of the times during resonance and that's why the right ring reacts. Thanks!What's the first step of Birch Reduction? Donation of electron from Sodium Atom. If my memory serves right, I think those carbon atoms which suffers from shortage of electrons will be able to accept that electron, in this case, the ring attached to -CN group.
I said to try making the resonating structures to get yourself the idea of effective electronic distribution in the compound.
For your sake, this question I solved it via Mechanism. Reality is I didn't know Birch Reduction, or any reduction for God's sake. I was only able to attempt this question because I saw its Mechanism afterward.
Sodium atom is donating an electron, so try getting that electron accepted where -CN can exhibit its -M effect.
Sorry, i meant the same, i don't know what made me to write that.Err... I meant the right ring is in electron debt due to -CN and that's why the lone electron from Sodium atom will be accepted by atoms bossed by -CN.