Textbook Question
Predict the theoretical number of different NMR signals produced by each compound, and give approximate chemical shifts. Point out any diastereotopic relationships.
c. Ph—CHBr—CH2Br
d. vinyl chloride
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15. Analytical Techniques:IR, NMR, Mass Spect
H NMR Table
Multiple Choice
Which of the labeled hydrogens will be most de-shielded?
A
A
B
B
C
C
D
D
E
E
Verified step by step guidance1
Identify the functional groups present in each structure. The presence of electronegative atoms or groups can influence the shielding of nearby hydrogens.
Consider the effect of electronegative atoms or groups on the chemical shift of hydrogens. Electronegative atoms can withdraw electron density, leading to de-shielding of nearby hydrogens.
Analyze the structure labeled B. It contains an ester functional group, which has an oxygen atom that can withdraw electron density from nearby hydrogens.
Compare the chemical environment of the hydrogens in each structure. The hydrogen in structure B is adjacent to an oxygen atom, which is more electronegative than the carbonyl carbon in the other structures.
Conclude that the hydrogen in structure B is the most de-shielded due to the presence of the electronegative oxygen atom in the ester group, which withdraws electron density more effectively than the other groups present in the other structures.
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