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Of the Hs attached to carbons A- D, which will be most downfield (farthest from zero) in the 'H NMR spectrum of the molecule below? the H₂C B A ABCD CH₂ D

Of the Hs attached to carbons A- D, which will be most downfield (farthest from zero) in the 'H NMR spectrum of the molecule below? the H₂C B A ABCD CH₂ D

Chemistry
Chemistry
10th Edition
ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Chapter1: Chemical Foundations
Section: Chapter Questions
Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...
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### Understanding Downfield Shifts in Proton NMR #### Question: Of the H's attached to carbons A-D, which will be most downfield (farthest from zero) in the ^1H NMR spectrum of the molecule below? #### Diagram: ``` H₂ O CH₃ H₃C─B─C─O─C─C─D O ``` The diagram shows the structure of a molecule with segments labeled as A, B, C, and D, where: - Carbon A is bonded to a methyl group (H₃C). - Carbon B is bonded to the carbonyl group (C=O). - Carbon C is bonded to an oxygen (O) and a carbonyl group (C=O) through an ester linkage. - Carbon D is bonded to a methylene group (CH₂). #### Multiple Choice: - O A - O B - ● C - O D ### Explanation: In the context of ^1H NMR spectroscopy, the deshielding effect caused by electronegative atoms and functional groups will influence the chemical shift of hydrogen atoms attached to different carbons. Downfield shifts (higher ppm values) are associated with greater deshielding. Factors to consider include: 1. **Electronegativity of neighboring atoms/groups**: Oxygen and carbonyl groups (C=O) are highly electronegative, causing significant deshielding. 2. **Proximity to electronegative groups**: Hydrogens closer to these groups will be more deshielded. Analyzing the given structure, we observe: - **Hydrogens attached to carbon A (H₃C-)**: These are relatively shielded, being part of a methyl group without direct attachment to electronegative atoms. - **Hydrogens attached to carbon B**: These are close to a carbonyl group, resulting in noticeable deshielding. - **Hydrogens attached to carbon C**: Directly bonded to two electronegative groups (oxygen and carbonyl), inducing the most considerable downfield shift. - **Hydrogens attached to carbon D (CH₃)**: Despite being near a carbonyl group, it is less deshielded compared to those on carbon B and carbon C. Therefore, hydrogens attached to carbon **C** experience the most considerable downfield shift in the
Transcribed Image Text:### Understanding Downfield Shifts in Proton NMR #### Question: Of the H's attached to carbons A-D, which will be most downfield (farthest from zero) in the ^1H NMR spectrum of the molecule below? #### Diagram: ``` H₂ O CH₃ H₃C─B─C─O─C─C─D O ``` The diagram shows the structure of a molecule with segments labeled as A, B, C, and D, where: - Carbon A is bonded to a methyl group (H₃C). - Carbon B is bonded to the carbonyl group (C=O). - Carbon C is bonded to an oxygen (O) and a carbonyl group (C=O) through an ester linkage. - Carbon D is bonded to a methylene group (CH₂). #### Multiple Choice: - O A - O B - ● C - O D ### Explanation: In the context of ^1H NMR spectroscopy, the deshielding effect caused by electronegative atoms and functional groups will influence the chemical shift of hydrogen atoms attached to different carbons. Downfield shifts (higher ppm values) are associated with greater deshielding. Factors to consider include: 1. **Electronegativity of neighboring atoms/groups**: Oxygen and carbonyl groups (C=O) are highly electronegative, causing significant deshielding. 2. **Proximity to electronegative groups**: Hydrogens closer to these groups will be more deshielded. Analyzing the given structure, we observe: - **Hydrogens attached to carbon A (H₃C-)**: These are relatively shielded, being part of a methyl group without direct attachment to electronegative atoms. - **Hydrogens attached to carbon B**: These are close to a carbonyl group, resulting in noticeable deshielding. - **Hydrogens attached to carbon C**: Directly bonded to two electronegative groups (oxygen and carbonyl), inducing the most considerable downfield shift. - **Hydrogens attached to carbon D (CH₃)**: Despite being near a carbonyl group, it is less deshielded compared to those on carbon B and carbon C. Therefore, hydrogens attached to carbon **C** experience the most considerable downfield shift in the
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