Aromaticity and Molecular Orbital Theory

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What is the characteristic of the lowest-lying molecular orbital in cyclic conjugated molecules?

It is the only orbital that is not degenerate (correct)

It is always empty

It comes in a degenerate pair with another orbital

It is the highest-energy orbital

What is the total number of electrons required to fill the lowest-lying orbital and n succeeding energy levels in cyclic conjugated molecules?

4n + 2 (correct)

2n + 2

4n + 1

2n + 1

What is the characteristic of an aromatic compound according to Huckel's rule?

It has an odd number of pi electrons

It has a non-planar structure

It has 4n + 2 pi electrons (correct)

It has a localized pi electron system

What is the reason for the equivalence of all C-C bonds in benzene?

The p orbitals on each carbon atom overlap equally well with neighbouring p orbitals on both sides Signup and view all the answers

What is the characteristic of an antiaromatic compound?

It has a localized pi electron system Signup and view all the answers

What is the reason for cyclooctatetraene not being aromatic?

It has 8 pi electrons, which is not a multiple of 4n + 2 Signup and view all the answers

What is the main reason why the annulene with 10 π electrons is not aromatic?

The ring puckers to relieve the strain, preventing π electrons from delocalizing over the entire ring Signup and view all the answers

What is the condition for a heterocycle to be aromatic?

It must have at least one lone pair of electrons Signup and view all the answers

What is the result of increasing the number of fused benzene rings in Polycyclic Aromatic Hydrocarbons (PAHs)?

The number of resonance structures increases Signup and view all the answers

What is necessary for cyclic conjugation to occur in a molecule?

The molecule must have a planar ring with alternating double and single bonds Signup and view all the answers

What is the characteristic of a molecule that follows Huckel's rule?

It has a planar ring with $(4n + 2)$ π electrons Signup and view all the answers

What is the difference between benzene and napthalene in terms of resonance structures?

Benzene has two resonance structures, while napthalene has three Signup and view all the answers

What is the main difference between the lone pair of nitrogen in pyridine and the pi electrons in the aromatic ring?

The lone pair is localized on the nitrogen, while the pi electrons are delocalized. Signup and view all the answers

What is the hybridization of the carbon atoms in the pyridine ring?

sp2 Signup and view all the answers

How many pi electrons are present in the pyridine ring?

6 Signup and view all the answers

Why does pyridine obey Huckel's rule of aromaticity?

Because it has 6 pi electrons Signup and view all the answers

What is the shape of the p orbitals in the pyridine ring?

Perpendicular to the plane of the ring Signup and view all the answers