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Directing groups. What are directing groups?. Substitution of a 2 nd group on a benzene ring The 1 st group directs the position of the 2 nd substituted group Two types 2‐ and 4‐directing groups activate the ring: reactivity increases
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What are directing groups? • Substitution of a 2nd group on a benzene ring • The 1st group directs the position of the 2nd substituted group • Two types • 2‐ and 4‐directing groups activate the ring: reactivity increases • 3‐directing groups deactivate the ring: reactivity decreases
2- and 4- directing groups • 2- and 4- directing groups: –OH, NH2 • Group donates electrons onto ring • Reactivity increases • 2nd substitution at 2- or 4- positions 1 6 2 5 3 4 1 + 6 2 5 3 4 4
3- directing groups • 3- directing groups: –NO2 • Group withdraws electrons from ring • Reactivity decreases • 2nd substitution at 3- position 1 6 2 5 3 4 1 6 2 5 3 4