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

Look at the following pairs of structures carefully to identify them as representing a) completely different compounds, b) compounds that are structural isomers of each other, c) compounds that are geometric isomers of each other, d) conformers of the same compound (part of structure rotated around a single bond) or e) the same structure.

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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