Given that the third and fourth steps in the synthesis of Hagemann’s ester from ethyl acetoacetate are intramolecular aldol cyclization to yield a substituted cyclohexenone and a decarboxylation reaction. Both reactions are to be shown and products of each step are to be shown. Concept introduction: In intramolecular aldol reactions dicarbonyl compounds such as diketones react with a base to yield a cyclic enone as the products. The reaction occurs in three steps i) Abstraction of α-hydrogen by a base to yield an enolate anion ii) Attack of the anion on the carbonyl carbon in the same molecule iii) Protonation of the alkoxide intermediate. A β-ketoacid normally eliminates CO 2 on heating. To show: The third and fourth steps in the synthesis of Hagemann’s ester from ethyl acetoacetate, the intramolecular aldol cyclization to yield a substituted cyclohexenone and a decarboxylation reaction and further to show the products of these reactions.

Question

How many signals do you expect in the H NMR spectrum for this molecule? Br Br Write the answer below. Also, in each of the drawing areas below is a copy of the molecule, with Hs shown. In each copy, one of the H atoms is colored red. Highlight in red all other H atoms that would contribute to the same signal as the H already highlighted red. Note for advanced students: In this question, any multiplet is counted as one signal. Number of signals in the 'H NMR spectrum. For the molecule in the top drawing area, highlight in red any other H atoms that will contribute to the same signal as the H atom already highlighted red. If no other H atoms will contribute, check the box at right. No additional Hs to color in top molecule For the molecule in the bottom drawing area, highlight in red any other H atoms that will contribute to the same signal as the H atom already highlighted red. If no other H atoms will contribute, check the box at right. No additional Hs to color in bottom molecule

Answer 1

Question

Chapter 23.SE, Problem 72AP

Interpretation Introduction

Interpretation:

Given that the third and fourth steps in the synthesis of Hagemann’s ester from ethyl acetoacetate are intramolecular aldol cyclization to yield a substituted cyclohexenone and a decarboxylation reaction. Both reactions are to be shown and products of each step are to be shown.

Concept introduction:

In intramolecular aldol reactions dicarbonyl compounds such as diketones react with a base to yield a cyclic enone as the products. The reaction occurs in three steps i) Abstraction of α-hydrogen by a base to yield an enolate anion ii) Attack of the anion on the carbonyl carbon in the same molecule iii) Protonation of the alkoxide intermediate.

A β-ketoacid normally eliminates CO₂ on heating.

To show:

The third and fourth steps in the synthesis of Hagemann’s ester from ethyl acetoacetate, the intramolecular aldol cyclization to yield a substituted cyclohexenone and a decarboxylation reaction and further to show the products of these reactions.

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