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The proton NMR chemical shifts of the hydrogens in
Chapter 10, Problem 49SP(choose chapter or problem)
The proton \(N M R\) chemical shifts of the hydrogens in pyridine are shown. These are typical aromatic chemical shifts, except that the ortho protons (on the carbons bonded to nitrogen) are deshielded to \(\delta 8.60\). A suitable oxidizing agent (such as a peroxyacid) can add an oxygen atom to pyridine to give pyridine \(N-\text { oxide }\). The effect of this added oxygen atom is to shift the ortho protons upfield from \(\delta 8.60 \text { to } \delta 8.19\) The meta protons are shifted downfield from \(\delta 7.25\) to \(\delta 7.40\). The para protons are shifted upfield, from \(\delta 7.64 \text { to } \delta 7.32\) Explain this curious effect, shifting some protons upfield and others downfield.
Equation Transcription:
Text Transcription:
N M R
\delta 8.60
N-\text { oxide }
\delta 8.60 \text { to } \delta 8.19
\delta 7.25
\delta 7.40
\delta 7.64 \text { to } \delta 7.32
Questions & Answers
QUESTION:
The proton \(N M R\) chemical shifts of the hydrogens in pyridine are shown. These are typical aromatic chemical shifts, except that the ortho protons (on the carbons bonded to nitrogen) are deshielded to \(\delta 8.60\). A suitable oxidizing agent (such as a peroxyacid) can add an oxygen atom to pyridine to give pyridine \(N-\text { oxide }\). The effect of this added oxygen atom is to shift the ortho protons upfield from \(\delta 8.60 \text { to } \delta 8.19\) The meta protons are shifted downfield from \(\delta 7.25\) to \(\delta 7.40\). The para protons are shifted upfield, from \(\delta 7.64 \text { to } \delta 7.32\) Explain this curious effect, shifting some protons upfield and others downfield.
Equation Transcription:
Text Transcription:
N M R
\delta 8.60
N-\text { oxide }
\delta 8.60 \text { to } \delta 8.19
\delta 7.25
\delta 7.40
\delta 7.64 \text { to } \delta 7.32
ANSWER:
Solution 49SP