01 Feb Organic chemistry including alcohol, acid and esters
Chemistry tuition classes in Miracle Learning Centre are easy to understand and help you in the chemistry tuition application questions. If you do not understand chemistry in school, you must definitely come for chemistry tuition classes at Miracle Learning Centre. Let us learn about organic chemistry including alcohol, carboxylic acid and esters in this chemistry tuition lesson.
We are going to learn about organic chemistry mainly alcohol, carboxylic acid and esters. Ethanol is obtained from fermentation of glucose in the presence of yeast, at 37oC, in the absence of oxygen. Glucose is being fermented and ethanol and carbon dioxide is being collected. Carbon dioxide and be tested by passing carbon dioxide into lime water. If carbon dioxide is present, white precipitate of calcium carbonate will be formed. Other methods of obtaining ethanol is by hydration of ethene. Steam added to ethene undergoes addition reaction and forms ethanol. The conditions needed for this reaction is 300 degree Celsius, 70atm and phosphoric acid as catalyst. Ethanol undergo various reactions. Ethanol can react with reactive metals like sodium to form sodium ethoxide and hydrogen gas. Ethanol can be oxidized in the air to form ethanoic acid. This is explained when a bottle of wine is left open for a few days it will turn sour. This is because ethanol has been oxidized into ethanoic acid and tastes sour. The ethanoic acid that is formed tastes sour and hence the bottle of wine has to be thrown away.
Another way of oxidising ethanol is by undergoing oxidation by adding a suitable oxidizing agent. The two common oxidizing agent used are potassium dichromate(VI) and potassium manganate(VII). During the reaction, potassium dichromate(VI) will turn from orange to green and potassium manganate(VII) will turn from purple to colorless. This indicates that a redox reaction has taken place. When the reaction is complete, the final colour will be obtained. This process is done by heating under reflux.
Carboxylic acid on the other hand has a functional group of -COOH. Carboxylic acids are weak acids. Weak acids dissociate by partially in water to form a low concentration of hydrogen ions. On the other hand, strong acids like hydrochloric acid, sulfuric acid and nitric acid are strong acids. Strong acids dissociate completely to form a high concentration of hydrogen ions.
Carboxylic acids that we are talking about now consists of methanoic acid, ethanoic acid, propanoic acid, butanoic acid and pentanoic acid. These carboxylic acids are weak acids. Hence the universal indicator colour will turn orange or yellow. Carboxylic acid like ethanoic acid undergoes similar reactions as strong acids like hydrochloric acid. For example, ethanoic acid react with magnesium, which is reactive metal, to form sodium ethanoate and hydrogen gas. This is an example of an acid reacting with a reactive metal to form salt and hydrogen gas. Ethanoic acid also reacts with sodium hydroxide to from sodium ethanoate and water. This is an example of an acid reacting with an alkaline to form salt and water. Lastly, ethanoic acid reacts with potassium carbonate to form potassium ethanoate, carbon dioxide and water. This is an example of an acid reacting with a metal carbonate to form salt, carbon dioxide and water.
Carboxylic acid undergo esterification by reacting with alcohol under the conditions of 200 degree Celsius and in the presence of concentrated sulfuric acid. Esterification takes place when ethanoic acid reacts with ethanol. The ester formed is ethyl ethanoate and water. Another example of esterification is when butanoic acid reacts with propanol. The ester formed is propyl butanoate and water.
Ester has a sweet smell and is commonly used in food flavorings. It makes the food more appetizing with a very pleasant and sweet smell. Perfume also uses ester and there is a big industry out there producing perfumes. If you are interested in learning more about perfumes, the study of chemistry of esters would be important to you. Esterification is an example of a condensation reaction where two molecules combine together to form a product with the elimination of a small molecule(eg water).