Organic Chemistry
Organic Chemistry
6th Edition
ISBN: 9781936221349
Author: Marc Loudon, Jim Parise
Publisher: W. H. Freeman
Question
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Chapter 12, Problem 12.10P
Interpretation Introduction

(a)

Interpretation:

Whether the CC stretch in the compound CH3CH2CH2CH2CCH is IR active or IR inactive is to be stated.

Concept introduction:

The IR rays are able to stretch the bond in the compound as they carry the energy sufficient to perform this task. The compound is said to be IR active if the energy absorbed the bond leads to change in the dipole moment of the molecule.

Expert Solution
Check Mark

Answer to Problem 12.10P

The CC stretch in the compound CH3CH2CH2CH2CCH is IR active.

Explanation of Solution

Change in the dipole moment of the molecule on IR absorption is the necessary condition to be IR active.

The CC stretch in the compound CH3CH2CH2CH2CCH leads to change in the dipole moment of the molecule as the molecule is unsymmetrical about the CC bond.

Therefore, CC stretch in the compound CH3CH2CH2CH2CCH is IR active.

Conclusion

The CC stretch in the compound CH3CH2CH2CH2CCH is IR active due to the change in the dipole moment of the molecule.

Interpretation Introduction

(b)

Interpretation:

Whether the C=O stretch in the compound (CH3)2C=O is IR active or IR inactive is to be stated.

Concept introduction:

The IR rays are able to stretch the bond in the compound as they carry the energy sufficient to perform this task. The compound is said to be IR active if the energy absorbed the bond leads to change in the dipole moment of the molecule.

Expert Solution
Check Mark

Answer to Problem 12.10P

The C=O stretch in the compound (CH3)2C=O is IR active.

Explanation of Solution

Change in the dipole moment of the molecule on IR absorption is the necessary condition to be IR active.

The C=O stretch in the compound (CH3)2C=O leads to change in the dipole moment of the molecule. The C=O bond is a polar bond already and if the bond is stretched then the distance of charge separation will change and thus the dipole moment as well.

Therefore, C=O stretch in the compound (CH3)2C=O is IR active.

Conclusion

The C=O stretch in the compound (CH3)2C=O is IR active due to the change in the dipole moment of the molecule.

Interpretation Introduction

(c)

Interpretation:

Whether the cyclohexane ring “breathing” or simultaneous stretching of the all CC bonds is IR active or IR inactive is to be stated.

Concept introduction:

The IR rays are able to stretch the bond in the compound as they carry the energy sufficient to perform this task. The compound is said to be IR active if the energy absorbed the bond leads to change in the dipole moment of the molecule.

Expert Solution
Check Mark

Answer to Problem 12.10P

The simultaneous stretch of all CC bonds stretch in the cyclohexane is IR inactive.

Explanation of Solution

Change in the dipole moment of the molecule on IR absorption is the necessary condition to be IR active.

The simultaneous stretch of all CC bonds stretch in the cyclohexane does not lead to change in the dipole moment of the molecule. The simultaneous stretch of CC bonds in the cyclohexane leads to an increase in the size of the ring but the ring is still symmetric and does not have any polar bond and therefore, no change in the dipole moment.

Therefore, simultaneous stretch of all CC bonds stretch in the cyclohexane is IR inactive.

Conclusion

The simultaneous stretch of all CC bonds stretch in the cyclohexane is IR inactive due to the change in the dipole moment of the molecule.

Interpretation Introduction

(d)

Interpretation:

Whether the CC stretch in the compound CH3CH2CCCH2CH3 is IR active or IR inactive is to be stated.

Concept introduction:

The IR rays are able to stretch the bond in the compound as they carry the energy sufficient to perform this task. The compound is said to be IR active if the energy absorbed the bond leads to change in the dipole moment of the molecule.

Expert Solution
Check Mark

Answer to Problem 12.10P

The CC stretch in the compound CH3CH2CCCH2CH3 is IR inactive.

Explanation of Solution

Change in the dipole moment of the molecule on IR absorption is the necessary condition to be IR active.

The CC stretch in the compound CH3CH2CCCH2CH3 does not lead to change in the dipole moment of the molecule as the molecule is symmetrical about the CC bond.

Therefore, CC stretch in the compound CH3CH2CCCH2CH3 is IR inactive.

Conclusion

The CC stretch in the compound CH3CH2CCCH2CH3 is IR inactive due to the no change in the dipole moment of the molecule.

Interpretation Introduction

(e)

Interpretation:

Whether the symmetrical stretching of the NO bond in nitromethane is IR active or IR inactive is to be stated.

Concept introduction:

The IR rays are able to stretch the bond in the compound as they carry the energy sufficient to perform this task. The compound is said to be IR active if the energy absorbed the bond leads to change in the dipole moment of the molecule.

Expert Solution
Check Mark

Answer to Problem 12.10P

The symmetric stretch of NO bond in the nitromethane is IR active.

Explanation of Solution

Change in the dipole moment of the molecule on IR absorption is the necessary condition to be IR active.

The symmetric stretch of NO bond in the nitromethane leads to change in the dipole moment of the molecule. The NO bond is a polar bond and the symmetric stretch of NO bond will lead to change in the distance between the charge separation and therefore, in the dipole moment.

Therefore, symmetric stretch of NO bond in the nitromethane is IR active.

Conclusion

The symmetric stretch of NO bond in the nitromethane is IR active due to the change in the dipole moment of the molecule.

Interpretation Introduction

(f)

Interpretation:

Whether the CCl bond stretch in (CH3)3CCl is IR active or IR inactive is to be stated.

Concept introduction:

The IR rays are able to stretch the bond in the compound as they carry the energy sufficient to perform this task. The compound is said to be IR active if the energy absorbed the bond leads to change in the dipole moment of the molecule.

Expert Solution
Check Mark

Answer to Problem 12.10P

The stretch of CCl bond in the (CH3)3CCl is IR active.

Explanation of Solution

Change in the dipole moment of the molecule on IR absorption is the necessary condition to be IR active.

The stretch of CCl bond in the (CH3)3CCl leads to change in the dipole moment of the molecule. The CCl bond is a polar bond and the stretch of CCl bond will lead to change in the distance between the charge separation and therefore, in the dipole moment.

Therefore, stretch of CCl bond in the (CH3)3CCl is IR active.

Conclusion

The stretch of CCl bond in the (CH3)3CCl is IR active due to the change in the dipole moment of the molecule.

Interpretation Introduction

(g)

Interpretation:

Whether the C=C stretch in the compound trans-3-hexene is IR active or IR inactive is to be stated.

Concept introduction:

The IR rays are able to stretch the bond in the compound as they carry the energy sufficient to perform this task. The compound is said to be IR active if the energy absorbed the bond leads to change in the dipole moment of the molecule.

Expert Solution
Check Mark

Answer to Problem 12.10P

The C=C stretch in the compound trans-3-hexene is IR inactive.

Explanation of Solution

Change in the dipole moment of the molecule on IR absorption is the necessary condition to be IR active.

The structure of trans-3-hexene is shown below.

Organic Chemistry, Chapter 12, Problem 12.10P

Figure 1

The C=C stretch in the compound trans-3-hexene does not lead to change in the dipole moment of the molecule as the molecule is symmetrical about the C=C bond.

Therefore, C=C stretch in the compound trans-3-hexene is IR inactive.

Conclusion

The C=C stretch in the compound trans-3-hexene is IR inactive due to the no change in the dipole moment of the molecule.

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