# Most activated position for Electrophilic addition in substituted biphenyls

I know the first structure will go fastest electrophilic addition due to +mesomeric effect but I was wondering what would be the product(major) if a electrophile attacks

Will the electrophile attack both ring or the ring near to $\ce{OH}$ group? Also the negative charge due to resonance will resonate on both the rings then how will I decide which ring to attack to give me major product?

According to me, the ortho positions of the ring near the $\ce{OH}$ group will have a negative charge - as well as the para position - but the para position is hindered. So, the electrophile will attack the ortho positions.

If this the correct explanation of the question, then I have one more question as well, that: when negative charge delocalises to the para position, it can delocalise to the other ring as well. Then, the electrophile could attack in the second ring also, where the negative charge would be generated by resonance. So, will the electrophile attack-the first ring or the second ring?

• Addition not substitution. – Mithoron Mar 30 '18 at 22:09
• @Mithoron sorry my bad – user190625 Mar 30 '18 at 22:16
• Note that electrophile could attack alkene as well. – Mathew Mahindaratne Mar 30 '18 at 23:11
• @MathewMahindaratne so will there be multiple major products – user190625 Mar 31 '18 at 15:44
• @user190625 I hope you understand that EAS and electrophilic addition are different. Electrophilic addition will take place on the pi bond alone. – Gaurang Tandon Apr 1 '18 at 1:03