Question

Objectives - Section 1 • Identify a substituent as an ortho para director or a meta director, Draw the resonance structure that explains the relative directing ability of a specific substituent. Classify a substituent as an activating or a deactivating group. Explain why the halogens are ortho/para directors but are deactivators. • 1. Draw the mechanism of the reaction below and use resonance structures of the arenium ion intermediate to explain why the starting material is an ortho/para director

Answer 1

WALL Est Br2 no febra ne mechanism &- lo Bar-Br + Febrz sr-febru polarization o-c43 a Brc rebru → IT TO go Br Bye -o-cH3 Tor -o-CH3 ortho product @JO-CH3 - Bri - p-product polarization is formed formation of o-complex of - Bos In first step - In seand step arenium ion - In last step or tho& perra Aromatisation product is takes place formed

D (c.,Y) ieta $ TRACE Ester functioneel group is activator. activeeting group direct the incoming electrophile to either Ortho or para position. The attack at meta is not to fovoured. These fose call altivators are orthod parea directors. Halogens are found to be intersecting All of them are moderately deactivators but are ortho & perra-director. Thir treffect dominates ores their -I effect and hence of directing Activators in The group which have tI or tr effects increse the electron density in the benzene ring attack of electrophile on such aromatic ring is o than benzene therefore they are said to be be activater. -

о—сна О-СН3 ortho Ortho O-CH3 - П® у МАНА more steble -из — п meta — н. * пого Not. favorable. para O-CH2 На Вх — рерн — 6 на квт more stable ТВО