Huckel's Rule Video Lessons

Concept

# Problem: Indicate whether or not each of the following structures is considered to be aromatic.a) A is aromatic, B is not.b) B is aromatic, A is not.c) Both A and B are aromatic.d) A and B are not aromatic.

###### FREE Expert Solution

Four rules for aromaticity:

1.    Cyclic

2.    Fully conjugated

3.    Planar

4.    Huckel’s rule (4n+2 pi electrons)

• The variable “n” stands for the number of pi electrons found in the would-be aromatic portion of a molecule.
• The pi electrons can be found in pi bonds (like those in alkenes and alkynes) and in lone pairs.

Structure A

1.    Cyclic: Yes

2.    Fully conjugated: Yes (pi bond and lone pair)

3.    Planar: Yes (Small ring)

4.    Huckel’s rule (4n+2 pi electrons)

• We have the pi bond (2 electrons) and the lone pair (2 electrons)
• 4 electrons total
• NOT 4n+2 electrons.

Not aromatic

Structure B

1.    Cyclic: Yes

2.    Fully conjugated: Yes (pi bonds and empty orbital/positive charge)

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###### Problem Details

Indicate whether or not each of the following structures is considered to be aromatic.

a) A is aromatic, B is not.

b) B is aromatic, A is not.

c) Both A and B are aromatic.

d) A and B are not aromatic.