Electrophilic Aromatic Substitution Reactions of Benzene

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This Demonstration shows a common class of reactions of benzene: electrophilic substitutions. In the first substitution, phase I, displaced electrons on the aromatic ring attract an electrophilic species , positively charged in almost all the cases. A carbocation is formed, stabilized by resonance contributions with increased positive charge in the ortho and para positions. In the first substitution phase II, protons, , are removed from the ring, thus restoring charge neutrality and aromaticity. Benzene is a planar molecule, with all of its bonds represented in black. The other bonds in the carbocation above and below the plane are colored in blue and red.

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The "time" button follows the breaking of old bonds and the formation of new ones. At the end of phase I, you can use the "charge location" command to move the positive charge.

After the first substitution, it is possible to make another one; this can be done more or less readily, depending on the nature of the first substituent. The "activating group" button places the second substituent in the ortho or para position (with fraction depending on temperature) while "deactivating group" places it in the meta position, as is shown by the "second substitution" [1].

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Contributed by: D. Meliga and S. Z. Lavagnino (January 2018)
Open content licensed under CC BY-NC-SA


Snapshots


Details

Snapshot 1: in the first phase, benzene undergoes attack from an electrophilic species

Snapshot 2: in the second phase, the carbocation loses the hydrogen at the point of the attack

Snapshot 3: the result of the second substitution is determined by the first substitution

Reference

[1] H. Hart, L. E. Craine and D. J. Hart, Organic Chemistry: A Short Course, 10th ed., Boston: Houghton Mifflin, Co., 1999.



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