The substance normally called "phenol" is the simplest of the family of phenols. Phenol has an -OH group attached to a benzene ring - and nothing else. The reaction between ethanoyl chloride and phenol is similar to the ethanol reaction although not so vigorous. Phenyl ethanoate is formed together with hydrogen chloride gas. Improving the reactions between phenols and some less reactive acyl chlorides. The -COCl group is attached directly to a benzene ring. It is much less reactive than simple acyl chlorides like ethanoyl chloride.
The phenol is first converted into the ionic compound sodium phenoxide sodium phenate by dissolving it in sodium hydroxide solution. The phenoxide ion reacts more rapidly with benzoyl chloride than the original phenol does, but even so you have to shake it with benzoyl chloride for about 15 minutes. Solid phenyl benzoate is formed.
This reaction can again be used to make esters from both alcohols and phenols. The reactions are slower than the corresponding reactions with acyl chlorides, and you usually need to warm the mixture. In the case of a phenol, you can react the phenol with sodium hydroxide solution first, producing the more reactive phenoxide ion. Taking ethanol reacting with ethanoic anhydride as a typical reaction involving an alcohol: There is a slow reaction at room temperature or faster on warming.
Solubility in water The small esters are fairly soluble in water but solubility falls with chain length. The reason for the solubility is that although esters can't hydrogen bond with themselves, they can hydrogen bond with water molecules.
Carboxylic acids and alcohols are often warmed together in the presence of a few drops of concentrated sulphuric acid in order to observe the smell of the esters formed. Because the reactions are slow and reversible, you don't get a lot of ester produced in this time. Carboxyl groups are weak acids , dissociating partially to release hydrogen ions. The carboxyl group symbolized as COOH has both a carbonyl and a hydroxyl group attached to the same carbon atom, resulting in new properties.
The reaction mixture is poured over ice to precipitate the crude product. Ice is used because the reaction of concentrated acids, especially concentrated sulfuric acid, with water is very exothermic. This would lead to the hydrolysis of the ester function during this step. Esters are produced when acids are heated with alcohols in a process called esterification.
An ester can be made by an esterification reaction of a carboxylic acid and an alcohol. The chemistry of the reaction Esters are produced when carboxylic acids are heated with alcohols in the presence of an acid catalyst. The catalyst is usually concentrated sulphuric acid. Dry hydrogen chloride gas is used in some cases, but these tend to involve aromatic esters ones containing a benzene ring.
In a redox reaction, electrons are transferred. The atom that gets electrons has been reduced and the atom that loses electrons had been oxidized. An esterification is when an alcohol and a carboxylic acid combine to make an ester.
Concentrated sulfuric acid is used as a catalyst to speed up the rate at which the ester is formed 6. Play the game now! The ester we synthesised above is impure. The round bottom flask now contains a mixture of organic and inorganic substances as shown below:. We will need to isolate the part of the mixture that contains the ester. We can do this by taking advantage of the ester's low solubility in water, and, the fact that the ester will be less dense than water so it will float on top of a layer of water.
We use a piece of glassware called a separating funnel to isolate the less dense ester layer from the aqueous layer as described in the steps below:. With the stopcock closed, pour the cooled mixture into a separating funnel containing about 20 mL of water. Stopper the funnel and shake.
Allow the layers to separate. With the separating funnel suspended above a conical fask erlenmeyer flask and the stopper removed, open the stopcock and allow the more dense aqueous layer to flow into the conical flask.
Close the stopcock. Repeat the process above by adding more water and then separating the layers. This should remove most of the water soluble species that is the acids and the alcohol. Add 5 mL sodium carbonate solution to neutralise acid still present 7. Swirl the flask until the production of carbon dioxide gas is no longer vigorous. Repeat this process until no more carbon dioxide gas is produced. Allow the mixture to stand so that it separates into layers, then remove the denser aqueous layer by opening the stopcock.
Close the stopcock once the aqueous layer has been run out. Wash the remaining organic layer with about 20 mL of water, stand to allow the layers to separate, then open the stopcock once more to run out the aqueous layer.
Close the stopcock once the aqueous layer has been removed. Add a small amount of anhydrous magnesium sulfate to a clean, dry conical flask. Run the remaining organic contents of the separating funnel into the conical flask. Stopper the conical flask and allow to stand for 15 minutes.
Decant the contents of the conical flask into a clean, dry, 50 mL round bottom flask. Initial washing with water will remove most of the water soluble species which includes any excess alcohol ethanol , carboxylic acid acetic acid , and sulfuric acid. Notice that the ester is named the opposite way around from the way the formula is written. The "ethanoate" bit comes from ethanoic acid. The "ethyl" bit comes from the ethyl group on the end.
Note: In my experience, students starting organic chemistry get more confused about writing names and formulae for esters than for almost anything else - particularly when it comes to less frequently met esters like the ones coming up next. Take time and care to make sure you understand!
Remember that the acid is named by counting up the total number of carbon atoms in the chain - including the one in the -COOH group. Note: You can find more about naming acids and esters by following this link to a different part of this site. The chemistry of the reaction Esters are produced when carboxylic acids are heated with alcohols in the presence of an acid catalyst.
The catalyst is usually concentrated sulphuric acid. Dry hydrogen chloride gas is used in some cases, but these tend to involve aromatic esters ones containing a benzene ring.
If you are a UK A level student you won't have to worry about these. The esterification reaction is both slow and reversible. So, for example, if you were making ethyl ethanoate from ethanoic acid and ethanol, the equation would be:.
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