Self-test questions: Chapter 22

.

The delocalised intermediate carbocation formed in the rate-determining step of the electrophilic substitution reaction is called the Wheland intermediate or sigma complex. This carbocation is ….

Aromatic

Non-aromatic

.

For the bromination of benzene which additional reagent is required (in addition to the Lewis acid (FeBr₃) shown).

Br₂

Cl₂

HBr

H₂SO₄

.

Select which statements below are true. Please select all that apply.

Aromatic compounds are cyclic, planar, and have an uninterrupted ring of 4n pi-electrons.

Anti-aromatic compounds are cyclic, planar, and have an uninterrupted ring of 4n pi-electrons.

Aromatic compounds are cyclic, planar, and have an uninterrupted ring of 4n + 2 pi-electrons.

Aromatic compounds cannot be charged.

.

Select which statements below are true. Please select all that apply.

Activating groups are groups that donate electrons into the benzene ring by positive inductive effects (+I) and/or positive mesomeric effects (+M).

Activating groups are groups that withdraw electrons from the benzene ring by negative inductive effects (-I) and/or negative mesomeric effects (-M).

Electron-withdrawing groups increase the reactivity of the ring to reaction with electrophiles because the carbocation is stabilised by electron withdrawing groups.

Electron-donating groups increase the reactivity of the ring to reaction with electrophiles because the carbocation is stabilised by electron donating groups.

.

Select which statements below are true with regard to amines as directing groups in electrophilic substitution reactions. Please select all that apply.

Amines are deactivating directing groups and generally result in mono-substitution on the aromatic ring.

Amines are strongly activating directing groups and generally result in poly-substitution on the aromatic ring.

Amines are ortho- and para- (2-, 4-) directing groups.

Amines are meta- (3-) directing groups.

.

Hückel's rule states that for cyclic compounds the number of pi-electrons must be equal to 4n + 1

True

False

.

[14]Annulenes are anti-aromatic

True

False

.

Halogens (eg. bromine and chlorine) are deactivating, ortho-, para- (2-, 4-) directors for electrophilic substitution reactions.

True

False

Self-test questions: Chapter 22

Quiz Content