Interpret the 1 H NMR of aspirin. Report integration, chemical shift (expected a

Question

Interpret the 1H NMR of aspirin. Report integration, chemical shift (expected and observed), and splitting patterns for each signal in table format. Clearly assign each signal to the structure. You may list a range of expected chemical shifts where appropriate but you are graded on proper assignments of all signals to observed shifts.

H NMR Substitution Patterns Predict the number of signals and multiplicity for each. Monosubstituted ortho-Disubstituted ortho-Disubstituted meta-Disubstituted H 2H doublet 2H triplet 1H triplet Synthesis of Aspirin predict integration, splitting, and chemical shifts for each proton. Use the simplified NMR tables posted on eCommons. Don't forget to include "observed chemical shifts" when interpreting the spectrum of aspirin. O O HaC OHR O Hc OH OHA Salicylic Acid Acetylsalicylic Acid (Aspirin) Signal int Splitting Expected Signal Int Splitting Expected 8 (#H's) (m) (m) (ppm) A'

Explanation / Answer

Prediction of spectrum for,

Monosubstituted benzene (Z)

2H doublet for ortho protons

2H triplet for meta protons

1H triplet for para proton

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ortho-disubstituted benzene (Z,Z)

2H doublet for ortho protons

2H triplet for meta protons

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ortho-disubstituted benzene (Z,Y)

1H doublet for ortho proton to Z

1H doublet for ortho proton to Y

1H triplet for meta proton to Z

1H triplet for meta proton to Y

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meta-disubstituted benzene (Z,Z)

1H singlet for ortho proton to both Z (internal)

2H doublet for ortho protons (external)

1H triplet for meta proton to both Z

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Signal assignment of salicylic acid and aspirin

For salicylic acid

A : 11 ppm (signlet, 1H)

B : 2.0 ppm (singlet, 1H)

C : 6.7 ppm (doublet, 1H)

D : 7.5 ppm (triplet, 1H)

E : 7.5 ppm (triplet, 1H)

F : 7.9 ppm (doublet, 1H)

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For Aspirin

A : 10.7 ppm

B : 2.3 ppm (singlet, 3H)

C : 7.2 ppm (doublet, 1H)

D : 7.3 ppm (triplet, 1H)

E : 7.8 ppm (triplet, 1H)

F : 8.2 ppm (doublet, 1H)

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