Waiting
Login-Verarbeitung ...

Trial ends in Request Full Access Tell Your Colleague About Jove

18.16: Directing Effect of Substituents: orthopara-Directing Groups

TABLE OF
CONTENTS
JoVE Core
Organic Chemistry

Ein Abonnement für JoVE ist erforderlich, um diesen Inhalt ansehen zu können. Melden Sie sich an oder starten Sie Ihre kostenlose Testversion.

Education
Directing Effect of Substituents: orthopara-Directing Groups
 
TRANSCRIPT

18.16: Directing Effect of Substituents: orthopara-Directing Groups

Orthopara directors are substituent groups attached to the benzene ring and direct the addition of an electrophile to the positions ortho or para to the substituent. All electron-donating groups are considered orthopara directors. They donate electrons to the ring and make the ring more electron-rich. The ring is therefore susceptible to the addition of electrophiles. Substituents such as amino, hydroxy, or alkoxy, containing lone pairs on the atom adjacent to the ring, donate electrons through resonance. For instance, phenol can undergo nitration at either ortho, meta, or para positions. However, the ortho and para carbocation intermediates are more stable than the meta intermediate because they have more resonance forms. Moreover, a particular favorable form in ortho and para carbocation intermediates exists—the one arising from the donation of oxygen’s nonbonding electrons.

Alkyl substituents without lone pairs also function as orthopara directors. They donate electrons through an inductive effect. The carbocation intermediates involved in the orthopara attack are more stable than meta. The orthopara directors function by stabilizing a positive charge directly on the methyl-substituted carbon. Since it is a tertiary position, the positive charge can be stabilized by the electron-donating inductive effect of the methyl group.

Tags

Ortho-para Directing Electron-donating Electrophilic Aromatic Substitution Resonance Stabilization Inductive Effect Carbocation Intermediate Phenol Nitration Alkyl Substituents

Get cutting-edge science videos from JoVE sent straight to your inbox every month.

Waiting X
Simple Hit Counter