Hepworth, Waring and Waring (2002) mentions that:
In general, electron-withdrawing substituents make the arene more susceptible to reduction, while the opposite applies for electron-donating substituents.
They then go on to say:
Methoxybenzene (anisole) is reduced more rapidly than benzene under Birch conditions. This is an exception to the rule, the reasons for which are not clear.
Why is this the case? Does anyone know of any possible explanations?
Source: Wikipedia Commons
Also, I was thinking, since the methoxy group donates electron density mesomerically to the ortho and para positions, wouldn't it be unfavourable for the carbanion to form that the ortho positions? This seems to happen in the mechanism shown above.
Lastly, I understand that the dispute between whether it is "Mechanism O" or "Mechanism M" was settled a while ago but I've read that the evidence pointing to "Mechanism O" seems to be computational studies and experiments. However, there has yet to be any qualitative explanations, based on chemistry principles and concepts, as to why "Mechanism O" is the one which occurs to a greater extent. I was wondering if anyone knows of any such explanations?
Hepworth, J. D., Waring, D. R., & Waring, M. J. (2002). Aromatic Chemistry. United Kingdom: The Royal Society of Chemistry.