The given compounds caffeine and theobromine are to be classified as pyrimidine and purine. The fact that one of these two cannot isomerize to an enolic form, while two different enols are possible for the other is to be explained. The structural formulas for the possible enols is to be written. Concept introduction: The purines and pyrimidines are nitrogen bases that constitute the structural unit of nucleic acids. Both purines and pyrimidines are nitrogen containing heterocyclic aromatic compounds . The structures of pyrimidine and purine are shown below: The structure of pyrimidine resembles that of benzene and pyridine having two nitrogen atoms. In the structure of purine, the prymidine ring is fused with imidazole ring and has four nitrogen atoms. The structure having an acidic hydrogen at alpha position to ketone (carbonyl carbon) can tautomerize into a keto-enol form.

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Chapter 27.1, Problem 3P

Interpretation Introduction

Interpretation:

The given compounds caffeine and theobromine are to be classified as pyrimidine and purine. The fact that one of these two cannot isomerize to an enolic form, while two different enols are possible for the other is to be explained. The structural formulas for the possible enols is to be written.

Concept introduction:

The purines and pyrimidines are nitrogen bases that constitute the structural unit of nucleic acids.

Both purines and pyrimidines are nitrogen containing heterocyclic aromatic compounds.

The structures of pyrimidine and purine are shown below:

The structure of pyrimidine resembles that of benzene and pyridine having two nitrogen atoms.

In the structure of purine, the prymidine ring is fused with imidazole ring and has four nitrogen atoms.

The structure having an acidic hydrogen at alpha position to ketone (carbonyl carbon) can tautomerize into a keto-enol form.

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Done 11:14 ⚫ worksheets.beyondlabz.com 5 (a). Using the peak information you listed in the tables for both structures, assign each peak to that portion of the structure that produces the peak in the NMR spectrum. Draw this diagram on your own sheet of paper and attach the sketch of your drawing to this question. Question 6 5 (b). Using the peak information you listed in the tables for both structures, assign each peak to that portion of the structure that produces the peak in the NMR spectrum. Draw this diagram on your own sheet of paper and attach the sketch of your drawing to this question. Question 7 6. Are there any differences between the spectra you obtained in Beyond Labz and the predicted spectra? If so, what were the differences? <

2. Predict the NMR spectra for each of these two compounds by listing, in the NMR tables below, the chemical shift, the splitting, and the number of hydrogens associated with each predicted peak. Sort the peaks from largest chemical shift to lowest. **Not all slots must be filled** Peak Chemical Shift (d) 5.7 1 Multiplicity multiplate .......... 5.04 double of doublet 2 4.98 double of doublet 3 4.05 doublet of quartet 4 5 LO 3.80 quartet 1.3 doublet 6 Peak Chemical Shift (d) Multiplicity