aldol reaction
Aldol
In this preparative lab, an aldol (trans-p-anisalacetophenone) was produced from the reaction between p-anisaldehyde and acetophenone with the presence sodium hydroxide. The reaction also showed the importance of an enolate and the role it played in the mechanism. Sodium hydroxide acts as a catalyst in this experiment and is chosen because of its basic conditions and pH. The acetophenone carries an alpha hydrogen that has a pKa between 18 and 20. This alpha hydrogen is acidic because of its location near the carbonyl on acetophenone. When the sodium hydroxide is added, it deprotonates the hydrogen and creates an enolate ion. This deprotonation creates a nucleophilic carbon that can attack an electrophilic carbon (like a parent carbon of a carbonyl). This enolate ion is a resonance structure and the oxygen atom and the corresponding pi bond it can form can stabilize the negative charge. When the nucleophilic pi bond attacks the carbonyl carbon (the electrophile) it undergoes nucleophilic addition. This is often known as crossed-aldol condensation and creates a new carbon-carbon bond. Water can donate a proton and form a alpha-beta-hydroxyaldehyde. When performing mixed aldol reactions, there are two potential enolates that can form and two potential carbonyls that can serve as the electrophile. Without taking precautions, you will end up with many different similar products. In order to control mixed aldol reactions so they produce your desired product, you have to worry about the two enolates and two carbonyls. First off you do not mix them together but instead you separate them. The two carbonyls react and form the aldol. Our product was trans-p-anisalacetophenone and it was produced from the ketone reacting with the aldehyde. The ketone does not react with itself because the aldehyde is sterically favored and the carbon on it is more likely to be attacked by the nucleophile than the carbon on the ketone. If the ketone were to attack itself, much more
In this preparative lab, an aldol (trans-p-anisalacetophenone) was produced from the reaction between p-anisaldehyde and acetophenone with the presence sodium hydroxide. The reaction also showed the importance of an enolate and the role it played in the mechanism. Sodium hydroxide acts as a catalyst in this experiment and is chosen because of its basic conditions and pH. The acetophenone carries an alpha hydrogen that has a pKa between 18 and 20. This alpha hydrogen is acidic because of its location near the carbonyl on acetophenone. When the sodium hydroxide is added, it deprotonates the hydrogen and creates an enolate ion. This deprotonation creates a nucleophilic carbon that can attack an electrophilic carbon (like a parent carbon of a carbonyl). This enolate ion is a resonance structure and the oxygen atom and the corresponding pi bond it can form can stabilize the negative charge. When the nucleophilic pi bond attacks the carbonyl carbon (the electrophile) it undergoes nucleophilic addition. This is often known as crossed-aldol condensation and creates a new carbon-carbon bond. Water can donate a proton and form a alpha-beta-hydroxyaldehyde. When performing mixed aldol reactions, there are two potential enolates that can form and two potential carbonyls that can serve as the electrophile. Without taking precautions, you will end up with many different similar products. In order to control mixed aldol reactions so they produce your desired product, you have to worry about the two enolates and two carbonyls. First off you do not mix them together but instead you separate them. The two carbonyls react and form the aldol. Our product was trans-p-anisalacetophenone and it was produced from the ketone reacting with the aldehyde. The ketone does not react with itself because the aldehyde is sterically favored and the carbon on it is more likely to be attacked by the nucleophile than the carbon on the ketone. If the ketone were to attack itself, much more