[Chemistry Class Notes] Ethanol Pdf for Exam

Science is a stunning subject that involves experimentation and application of principles and concepts of the universe and its behaviour through a method of trial and error. Chemistry is the branch of science that involves the application of chemical processes including reactions and properties in nature. 

Definition

Ethanol or ethyl alcohol is an organic compound and a chemical liquid with the formula – C₂H₅OH. It is primarily used as a solvent.

 

To understand the chemical structure of ethanol, you first need to know what alkenes are. Alkenes are compounds that are made up of carbon and hydrogen with at least one double bond among two carbons. Ethene is one such alkene. Unlike ethane where there are single carbon bonds, ethene has double bonds. Its chemical formula is CH₂CH₂.

 

Hydroxyl Group

You also need to know what a hydroxyl group is. Hydroxyl is that functional group that contains one hydrogen and one oxygen atom – bonded together. This group is denoted as -OH. As you can see there is the minus symbol which means, it is negatively charged.

 

Now, when we try to name the compounds that have this hydroxyl group, we use the suffix ‘ol’. The ‘ol’ of ethanol or ethyl alcohol is there because of this reason.

 

From Ethene to Ethanol: Hydration of Ethene

Now that you know all the fundamentals related to ethyl alcohol or ethanol, let us examine how ethanol is obtained from ethene. 

 

To obtain ethanol from ethene, you need to add water to ethene in the presence of an acidic medium. The reaction will look like this 

 

CH₂=CH₂ + H₂O ( In presence of acidic medium or H+) → CH₃-CH₂-OH

 

What is this acidic medium? 

An acidic medium is any acid that has a higher concentration of hydrogen ions. In this case, people generally use H₂SO₄ as the acidic medium.

 

There are three steps involved in the conversion of ethene to ethanol. These steps are discussed below –

 

Step 1 :

First of all, we need hydronium ions for the process to start. How do we get that? As said we need the presence of an acidic medium. When this acidic medium ( generally H₂SO₄) comes in contact with water, we get the Hydronium ion. The reaction will look like this –

 

H₂O + H+ = H₃O

 

Now that we have the Hydronium ion, this ion will react with the ethene. At first, the double bond between the two carbons will break. So, one of the carbons among the two CH₂ compounds will get a positive charge and one will get a negative charge – because, after the bond breaks, one carbon loses electrons and the other gains. On the other hand, in the H₃O compound, the oxygen is positively charged. As a result, the neighbouring Hydrogen atom will donate an electrovalent bond to oxygen. Now that the Hydrogen becomes positively charged, it gets attracted to the negatively charged carbon of one of the CH₂ compounds. So ultimately the ethene becomes a member of the ethyl group and we get H₂O after H₃O breaks. The reaction will look like this – 

 

CH₂CH₂ + H₃O = CH₂CH₃ + H₂O

 

Step 2:

In the second step, the CH₂CH₃ and H₂O react with one another. The lone pair of O in the H₂O will get attracted to the positive C atom of CH₂. So the result is the attachment of H₂O with the CH₂ compound of CH₂CH₃. Since Oxygen has 3 bonds, it is positively charged.

 

Step 3:

The compound reacts with other water molecules and one of the hydrogen atoms from the attached H₂O gets attracted to the other H₂O. Thus the result is the formation of CH₃-CH₂-OH and H₃O. And this is how we get the ethyl alcohol.

 

Ethene To Ethyl Alcohol: In Brief 

Step 1 →a. Formation of H₃O from the reaction between acid and water. 

               b. Formation of CH₂CH₃ from the reaction of ethene with H₃O.

Step 2 → Formation of CH₂CH₃ with H₂O attached to the CH₂.

Step 3 → The H₂O attached to the CH₂ reacts with other H₂O and forms H₃O while the CH₂CH₃ compound ultimately results in CH₂CH₃OH.

 

Functional Group

The OH in the ethanol is known as the functional group. It is this functional group that provides ethanol with its characteristic properties.

 

Properties of Ethanol 

• Ethanol is colourless.

• It is liquid at room temperature.

• Ethanol mixes with water quite well.

• Ethanol is a combustible material. It produces CO₂, water vapour, heat and light when it is burnt in the presence of oxygen.

• Ethanol, when oxidised with monatomic oxygen, gives ethanoic acid.

• If Sodium and Ethanol react with one another, there will be the formation of Hydrogen and sodium ethoxide.

Uses of Ethanol

• Ethanol is used as fuel. Although it cannot be fully used as fuel because of its water absorption properties that can damage the engines, it is an environmentally-friendly fuel. If scientists manage to bring enough value out of ethanol as a fuel, it can be a great alternative to the traditional fuels that are sources of air pollution.

• Ethanol is also used as a solvent in the extraction process.

• Ethanol is the main ingredient in drinking alcohol. In other words, it is an intoxicating agent.

Why Ethanol Intoxicates Human Beings

Ethanol is an intoxicating agent. When people drink ethanol, the liver cannot purify or filter all of it at once. Hence it flows to different parts of the body including the brain. As ethanol reaches the brain, the compound obstructs the gaps that are there between the neurons. As the neurons cannot function properly, people become slower and slower. Their speeches become slurred and their bodies fail to maintain a proper motor neuron function. Additionally, the reward centre of the brain gets triggered upon drinking alcohol and dopamine gets released. This tricks the brain into thinking that ethanol is something good because it is making people happy. And people keep on drinking ethanol.

 

Drinking ethanol can cause a lot of undesired effects. Would you like to behave in a way that you won’t if you were sober? Would you like to say something that you wouldn’t have said if you were sober? In addition to that, because of the impairment of the proper functions of the body and brain, drinking ethanol leads to road accidents. A few hours of happiness can result in the whole life’s pain.

 

The beauty of chemistry is it reveals the ‘why’ of things. People have been preparing ethanol since Chemistry wasn’t there. Now with the help of Chemistry, we know how ethanol works, what are its properties and why it is unhealthy to drink too much ethanol.

 

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