Chapter 14, Problem 14.41P

Interpretation Introduction

(a)

Interpretation:

Whether the given molecule is aromatic, antiaromatic, or nonaromatic is to be determined.

Concept introduction:

The molecules, to be aromatic, must obey Hückel’s rule of $\text{(4n+2)π}$ electrons where $\text{n}$ is an integer. The aromatic molecules have planar, cyclic structures with a cyclic conjugated system. The antiaromatic molecules are also planar, cyclic with conjugated systems but have $\text{(4n)π}$ electrons. If the molecule does not satisfy any of these conditions, it is said to be nonaromatic.

Answer to Problem 14.41P

The given molecule is nonaromatic due to lack of planarity.

Explanation of Solution

The given structure is:

The molecule has total $\text{14π}$ electrons, out of which $\text{12π}$ electrons could form fully conjugated cyclic $\text{π}$ system, and the two $\text{π}$ electrons of the triple bond can be composed in a separate $\text{π}$ system as these are not in the orbital which is parallel to $\text{p}$ AOs. Thus, according to Hückel’s rule, the molecule should be antiaromatic, but due to the instability associated with antiaromaticity, the molecule resists planarity. As the molecule is not planar, it should be nonaromatic.

Conclusion

The molecule is determined as nonaromatic based on the structure planarity.

Interpretation Introduction

(b)

Interpretation:

Whether the given molecule is aromatic, antiaromatic, or nonaromatic, is to be determined.

Concept introduction:

The molecules, to be an aromatic, must obey Hückel’s rule of $\text{(4n+2)π}$ electrons where $\text{n}$ is an integer. The aromatic molecules have planar, cyclic structures with cyclic conjugated system. The antiaromatic molecules are also planar, cyclic with conjugated system but have $\text{(4n)π}$ electrons. If the molecule does not satisfy any of these conditions, it is said to be nonaromatic.

Answer to Problem 14.41P

The given molecule is nonaromatic due to lack of planarity.

Explanation of Solution

The given structure is:

The molecule has total $\text{12π}$ electrons, which could form fully conjugated cyclic $\text{π}$ system around the periphery. Thus, according to Hückel’s rule, the molecule should be antiaromatic, but the central carbon is ${\text{sp}}^{\text{3}}$ which does not get involved in resonance and resists planarity. As the molecule is not planar, it should be nonaromatic.

Conclusion

The molecule is determined as nonaromatic based on the structure planarity.

Interpretation Introduction

(c)

Interpretation:

Whether the given molecule is aromatic, antiaromatic, or nonaromatic, is to be determined.

Concept introduction:

The molecules, to be an aromatic, must obey Hückel’s rule of $\text{(4n+2)π}$ electrons where $\text{n}$ is an integer. The aromatic molecules have planar, cyclic structures with cyclic conjugated system. The antiaromatic molecules are also planar, cyclic with conjugated system but have $\text{(4n)π}$ electrons. If the molecule does not satisfy any of these conditions, it is said to be nonaromatic.

Answer to Problem 14.41P

The given molecule is aromatic as it is planar, has cyclic conjugation, and obeys Hückel’s rule.

Explanation of Solution

The given structure is:

The given molecule is planar and has total $\text{10π}$ electrons, which could form a fully conjugated cyclic $\text{π}$ system around the periphery. Thus, according to Hückel’s rule, the molecule should be aromatic.

Conclusion

The molecule is determined as aromatic based on the Hückel’s rule.

Interpretation Introduction

(d)

Interpretation:

Whether the given molecule is aromatic, antiaromatic, or nonaromatic, is to be determined.

Concept introduction:

The molecules, to be an aromatic, must obey Hückel’s rule of $\text{(4n+2)π}$ electrons where $\text{n}$ is an integer. The aromatic molecules have planar, cyclic structures with cyclic conjugated system. The antiaromatic molecules are also planar, cyclic with conjugated system but have $\text{(4n)π}$ electrons. If the molecule does not satisfy any of these conditions, it is said to be nonaromatic.

Answer to Problem 14.41P

The given molecule is nonaromatic due non cyclic conjugated system.

Explanation of Solution

The given structure is:

The molecule has a conjugated system of total $\text{6π}$ electrons, but the molecule is not cyclic, thus, no cyclic conjugated system. Therefore, the molecule should be nonaromatic.

Conclusion

The molecule is determined as nonaromatic based on the non cyclic structure which lacks cyclic conjugation.

Interpretation Introduction

(e)

Interpretation:

Whether the given molecule is aromatic, antiaromatic, or nonaromatic, is to be determined.

Concept introduction:

The molecules, to be an aromatic, must obey Hückel’s rule of $\text{(4n+2)π}$ electrons where $\text{n}$ is an integer. The aromatic molecules have planar, cyclic structures with cyclic conjugated system. The antiaromatic molecules are also planar, cyclic with conjugated system but have $\text{(4n)π}$ electrons. If the molecule does not satisfy any of these conditions, it is said to be nonaromatic.

Answer to Problem 14.41P

The given molecule is aromatic as it is planar, has cyclic conjugation, and obeys Hückel’s rule.

Explanation of Solution

The given structure is:

The molecule is planar and has fully cyclic conjugated system of total $\text{4π}$ electrons because one of the lone pair on oxygen participates in the resonance. Therefore, according to Hückel’s rule of $\text{(4n+2)π}$ electrons, the molecule should be aromatic.

Conclusion

The molecule is determined as aromatic based on planarity, fully conjugated system, and having Hückel’s rule of $\text{(4n+2)π}$ electrons.

Interpretation Introduction

(f)

Interpretation:

Whether the given molecule is aromatic, antiaromatic, or nonaromatic, is to be determined.

Concept introduction:

The molecules, to be an aromatic, must obey Hückel’s rule of $\text{(4n+2)π}$ electrons where $\text{n}$ is an integer. The aromatic molecules have planar, cyclic structures with cyclic conjugated system. The antiaromatic molecules are also planar, cyclic with conjugated system but have $\text{(4n)π}$ electrons. If the molecule does not satisfy any of these conditions, it is said to be nonaromatic.

Answer to Problem 14.41P

The given molecule is nonaromatic as it is not conjugated and does not obey Hückel’s rule.

Explanation of Solution

The given structure is:

The molecule has only $\text{2π}$ electrons and nitrogen is ${\text{sp}}^{\text{3}}$ hybridized which prevents the conjugation. Thus, it does not obey Hückel’s rule of $\text{(4n+2)π}$ electrons or $\text{(4n)π}$ electrons. Therefore, the molecule is nonaromatic.

Conclusion

The molecule is determined as nonaromatic based on the non-conjugated system of $\text{π}$ electrons.

Interpretation Introduction

(g)

Interpretation:

Whether the given molecule is aromatic, antiaromatic, or nonaromatic, is to be determined.

Concept introduction:

The molecules, to be an aromatic, must obey Hückel’s rule of $\text{(4n+2)π}$ electrons where $\text{n}$ is an integer. The aromatic molecules have planar, cyclic structures with cyclic conjugated system. The antiaromatic molecules are also planar, cyclic with conjugated system but have $\text{(4n)π}$ electrons. If the molecule does not satisfy any of these conditions, it is said to be nonaromatic.

Answer to Problem 14.41P

The given molecule is nonaromatic as it has no cyclic conjugated system.

Explanation of Solution

The given structure is:

One of the lone pair on the oxygen atom participates in the resonance, thus, the molecule has $\text{6π}$ electrons but ${\text{sp}}^{\text{3}}$ hybridized carbon prevents the cyclic conjugation. Therefore, the molecule is nonaromatic.

Conclusion

The molecule is determined as nonaromatic based on non-conjugated system of $\text{π}$ electrons.