Chapter 19, Problem 32P

Interpretation Introduction

Interpretation:

Using ethyl propanoate as a starting material and any other required reagents, the synthesis of thymine is to be shown.

Concept introduction:

Electrophiles are electron-deficient species that have positive or partially positive charge. Lewis acids are electrophiles that accept electron pair.

Nucleophiles are electron-rich species that have negative or partially negative charge. Lewis bases are nucleophiles that donate electron pair.

Free radical is an atom, molecule, or ion that has an unpaired electron, which makes it highly chemically reactive.

Substitution reaction: A reaction in which one of the hydrogen atoms of a hydrocarbon or a functional group is substituted by any other functional group is called substitution reaction.

Elimination reaction: A reaction in which two substituent groups are detached and a double bond is formed is called elimination reaction.

Addition reaction: It is the reaction in which unsaturated bonds are converted to saturated molecules by the addition of molecules.

The carbon–carbon bond forming reaction, useful for the synthesis of beta keto ester, is known as Claisen condensation reaction.

In Claisen condensation, reaction occur between two esters, a carbon–carbon bond formation takes place which leads to the formation of $\beta -$ keto ester.

Dieckmann condensation is also known as intramolecular Claisen condensation.

Five and six membered rings are easily prepared by Dieckmann condensation.

Esters containing only one alpha hydrogen do not undergo Claisen condensation reaction.

The starting material ethyl propanoate undergoes Claisen condensation reaction in the presence of sodium ethoxide and forms a $\beta -$ dicarbonyl compound, which further reacts with urea in the presence of base which results in the formation of thymine.