Ethanol Formula: Structure, Formula, Composition, & Uses

Ethanol Formula: Did you know that the red fluid that rises in a thermometer is Ethanol? The alcohol present in alcoholic beverages is also Ethanol. It is commonly referred to as ethyl alcohol, pure alcohol, grain alcohol, and drinking alcohol, which is mostly known as the alcohol present in alcoholic beverages.
Ethanol is two-carbon alcohol, sometimes abbreviated as \({\rm{EtOH}}{\rm{.}}\) It is a constitutional isomer of dimethyl ether.

constitutional isomer of dimethyl ether. The ethyl group is represented as \(\left( {{{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{5}}}{\rm{ – }}} \right).\) It is flammable and volatile, so it evaporates easily when left in an open container.

Ethanol Structure

Ethanol Formula

The Ethanol structure is made of nine atoms that include two carbon \(\left( {\rm{C}} \right)\) atoms, six hydrogens \(\left( {\rm{H}} \right)\) atoms, and one oxygen \(\left( {\rm{O}} \right)\) atom. Hence, its chemical formula is \({{\rm{C}}_2}{{\rm{H}}_6}{\rm{O}}\) The chemical formula of Ethanol can also be written as \({\rm{C}}{{\rm{H}}_3}{\rm{C}}{{\rm{H}}_2}{\rm{OH}}\) or \({{\rm{C}}_2}{{\rm{H}}_5}{\rm{OH}}.\) An alternative notation \({\rm{C}}{{\rm{H}}_{\rm{3}}}{\rm{ – C}}{{\rm{H}}_{\rm{2}}}{\rm{ – OH}}\) is also used, which indicates that the carbon of a methyl group \(\left( {{\rm{C}}{{\rm{H}}_{\rm{3}}}{\rm{ – }}} \right)\) is attached to the carbon of a methylene group \(\left( {{\rm{ – C}}{{\rm{H}}_{\rm{2}}}{\rm{ – }}} \right),\) which is further attached to the oxygen of a hydroxyl group \({\rm{( – OH)}}{\rm{.}}\)

Ethanol Molar Mass

The Ethanol molar mass can be calculated as, \({{\rm{C}}_2}{{\rm{H}}_6}{\rm{O}} = 2\) (Atomic mass of Carbon)\(+6\)(Atomic mass of  hydrogen)\(+\)Atomic mass of Oxygen

\( = 2(12.01) + 6(1.007) + 15.999 = 46.07\;{\rm{g}}/{\rm{mol}}\)

Hence, one mole of Ethanol weighs \(46.07\) grams.

Hybridisation

Hybridisation is the process in which two or more atomic orbitals with almost the same energy levels mix to form new hybrid orbitals.

Ethanol gas is composed of two carbon atoms, and the first carbon atom is associated with four atoms which are: three hydrogens and one carbon. 

The \({\rm{C – 1}}\) atom is associated with four atoms which are: one oxygen, one carbon, and two hydrogen atoms.

Hence, Steric number of \({\rm{C – 1}}\) is\(=\)Number of atoms attached \(+\)Lone pairs \(=4+0=4\) 

The hybridisation of \({\rm{C – 1 = s}}{{\rm{p}}^{\rm{3}}}{\rm{(1s + 3p)}}\)

Thus \({\rm{C – 1}}\) carbon has \({\rm{s}}{{\rm{p}}^{\rm{3}}}\) hybridisation.

Hence, steric number of \({\rm{C – 2}}\) is\(=\)Number of atoms attached\(+\)Lone pairs

\({\rm{ = 4 + 0 = 4 = s}}{{\rm{p}}^{\rm{3}}}{\rm{(1s + 3p)}}\) 

Again, hybridisation has come up to \({\rm{s}}{{\rm{p}}^{\rm{3}}}\)  for the \({\rm{C – 2}}\) atom.

The oxygen atom forms two bonds as one with hydrogen, one with carbon, and the rest are two lone pairs of electrons.

Steric number of oxygen atom is\(=\)Number of atoms attached\(+\)Lone pairs\(=2+2=4\)

The hybridisation of oxygen\({\rm{ = s}}{{\rm{p}}^{\rm{3}}}{\rm{(1s + 3p)}}\)

Thus, we can say that the overall hybridisation state of Ethanol is \({\rm{s}}{{\rm{p}}^{\rm{3}}}.\)

Molecular Geometry

VSEPR or the Valence shell electron pair repulsion theory is used to find the molecular geometry of any compound.

According to the theory, the shape of any compound depends largely and solely on the number of bonding and lone pairs of electrons around the central atom. The compound takes up a shape that suits and makes it the most stable and has the least repulsion between different bonds. 

The carbon atoms in Ethanol gas have four bonds. Hence, according to the theory, the shape should be tetrahedral. However, the oxygen atom has two bonds and two lone pairs of electrons. Therefore, according to the theory, the oxygen atom will have a bent molecular shape.

The bond angle of Ethanol, after assessing its geometry, comes out to be somewhere around \({\rm{10}}{{\rm{9}}^{\rm{o}}}.\)

Bond Angle

All the carbon atoms in Ethanol are sp3 hybridised; hence the geometry will be tetrahedral. So, the bond angle of \({\rm{H}} – {\rm{C}} – {\rm{C}},{\rm{H}} – {\rm{C}} – {\rm{H}}\) and \({\rm{H}} – {\rm{C}} – {\rm{O}}\) is approx \({109^{\rm{o}}}{28^\prime }.\) In the case of the \({\rm{C}} – {\rm{O}} – {\rm{H}}\) bond, the oxygen atom is sp3 hybridised and contains two lone pairs of electrons. This causes a lone pair-bond pair repulsion and reduces the bond angle to \({\rm{10}}{{\rm{9}}^{\rm{o}}}.\)

Dipole Moment

Ethanol is polar in nature because of the presence of the hydroxyl group\(\left( {{\rm{ – OH}}} \right)\) attached to the carbon end. The hydroxyl group \(\left( {{\rm{ – OH}}} \right)\) is polar due to oxygen and a hydrogen atom.

The electronegativity of oxygen is \(3.44,\) and that of hydrogen is \(2.2.\) Being more electronegative, the oxygen atom attracts the bonded pair electron towards its side and gains a partial negative charge, whereas the hydrogen atom gains a relatively positive charge on it.

Due to the difference between the electronegativity of oxygen and the hydrogen atom, the hydroxyl group becomes polar. As a result, the molecule of ethanol gives a non zero dipole moment and becomes a polar molecule.

Lewis Structure

Lewis structure is a \({\rm{2 – D}}\) representation of all the bonding and nonbonding electron pairs of different atoms in a compound. 

Step 1: Calculating the valence electrons for each atom.

The valence electrons of the carbon atom is \(4,\) and here we have two atoms of carbon, so total valence electrons on \({\rm{C}}\) are \(=4*2=8.\)

Valence electrons for oxygen are \(=6.\)

Valence electrons for hydrogen are one, and here, we have six hydrogen atoms; thus, the total number of valence electrons for hydrogen is \(=6*1=6.\)

Hence, in ethanol we have a total of \(=8+6+6=20\) valence electrons.

Step 2: Making the electron dot structure.

Carbon, having the highest valency, is chosen as the central atom. This makes oxygen and hydrogen the neighbouring atoms.

Hydrogen needs a duplet to attain stability, whereas carbon and oxygen need \(8\) electrons each in their valence shell to fulfil the octet rule and reach stability. 

The \({\rm{1st}}\) carbon atom forms four bonds. Two bonds are with the hydrogen atom, and the other two bonds are one with the neighbouring carbon atom and one with the oxygen atom.

The \({\rm{2nd}}\) carbon forms four bonds, one with the neighbouring carbon atom and the rest three with hydrogen atoms. This carbon atom is thus stable as it has \(8\) electrons in its outermost shell.

Oxygen has \(6\) valence electrons. It shares two out of six valence electrons, one each with carbon and hydrogen. It is left with two lone pairs of electrons. Hence, the most stable electron dot structure that can be created for ethanol is as follows.

Skeletal Structure

The chemical structure of ethanol consists of a methyl group \(\left( {{\rm{C}}{{\rm{H}}_{\rm{3}}}{\rm{ – }}} \right)\) a methylene group \(\left( {{\rm{ – C}}{{\rm{H}}_{\rm{2}}}{\rm{ – }}} \right),\) and a hydroxyl group \({\rm{( – OH)}}{\rm{.}}\) There are four types of bonds in ethanol  as \({\rm{s}}{{\rm{p}}^{\rm{3}}}{\rm{ – 1s(C – H)}}\) sigma bond, \({\rm{s}}{{\rm{p}}^{\rm{3}}}{\rm{ – s}}{{\rm{p}}^{\rm{3}}}{\rm{(C – C)}}\) sigma bond, \({\rm{s}}{{\rm{p}}^{\rm{3}}}{\rm{ – s}}{{\rm{p}}^{\rm{3}}}{\rm{(C – O)}}\) sigma bond and \({\rm{s}}{{\rm{p}}^{\rm{3}}}{\rm{ – 1s(O – H)}}\) sigma bond. This is diagrammatically represented as below.

Preparation of Ethanol

Laboratory Preparation

A. From Ethene

Ethanol is prepared by the hydration of ethene in the presence of phosphoric acid, using an excess of steam under pressure at temperatures around \(300\,^\circ {\rm{C}}{\rm{.}}\)

A dilute solution of ethanol is obtained, which is concentrated by distillation that contains \(95.6\% \) ethanol by weight. 

B. By Fermentation

Ethanol in alcoholic beverages and fuel is produced by fermentation. Certain species of yeast (e.g., Saccharomyces cerevisiae) metabolise sugar, producing ethanol and carbon dioxide.

Fermentation is the process of culturing yeast under favourable thermal conditions to produce alcohol. This process is carried out at around \(35 – 40\,^\circ {\rm{C}}\left( {95 – 104\,^\circ {\rm{F}}} \right) – \)toxicity of Ethanol to yeast limits the ethanol concentration. Higher concentrations are obtained by fortification or distillation. The most ethanol-tolerant yeast strains can survive up to approximately \(18\% \) ethanol by volume.

Industrial Method

On the industrial scale, Ethanol is produced by the fermentation of molasses. Molasses is the mother liquor left after the crystallisation of sugarcane juice and contains about \(60\% \) fermentable sugar. The steps involved are:

1. Dilution of molasses: Molasses is first diluted with water in a \(1:5\) (molasses: water) ratio by volume.

2. Addition of Ammonium sulphate: Fortifying molasses with ammonium sulphate provides an adequate supply of nitrogen to yeast.

3. Addition of sulphuric acid: Fortified solution of molasses is then acidified with a small quantity of sulphuric acid. This enhances the growth of yeast but unfavours the growth of useless bacteria.

4. Fermentation: The resulting solution is received in a large tank, and yeast is added to it at \({\rm{35}}\,^\circ {\rm{C}}\) and kept for \(2\) to \(3\) days. During this period, enzymes sucrose and zymase present in yeast convert sugar into ethyl alcohol.

\({{\rm{C}}_{12}}{{\rm{H}}_{22}}{{\rm{O}}_{11}} + {{\rm{H}}_2}{\rm{O}} \to 2{{\rm{C}}_6}{{\rm{H}}_{12}}{{\rm{O}}_6}\)

\({{\rm{C}}_6}{{\rm{H}}_{12}}{{\rm{O}}_6} \to 2{{\rm{C}}_2}{{\rm{H}}_5}{\rm{OH}} + 2{\rm{C}}{{\rm{O}}_2}\)

5. Fractional distillation:  Alcohol obtained by the fermentation is called “wash”, which is about \(15\% \) to \(18\% \) pure. Using fractional distillation technique, it is converted into \(92\% \) pure alcohol known as rectified spirit or commercial alcohol.

Physical Properties

1. Pure ethanol is a colourless liquid.
2. Ethanol has a specific smell and burning taste.
3. Its boiling point is \({\rm{351}}\,{\rm{K}}\) which is higher than ethane.
4. It is soluble in water, i.e. it is miscible with water in all proportions.
5. It is highly volatile and flammable.
6. Its low melting point of \({\rm{ – 114}}.{\rm{5}}\,^\circ {\rm{C}}\) allows it to be used in antifreeze products.
7. Its density is \(789\;{\rm{g}}/{\rm{l,}}\) about \(20\% \) less than that of water.

Chemical Properties

1. Dehydration: Ethanol, when heated with conc. \({{\rm{H}}_2}{\rm{S}}{{\rm{O}}_4}\) or \({\rm{A}}{{\rm{l}}_2}{{\rm{O}}_3}\) at \({\rm{623}}\,{\rm{K}}\) undergoes dehydration, i.e. loses water molecule to form an alkene.

2. Reaction with sodium: Alcohols are weakly acidic. Ethanol reacts with sodium metal to form sodium ethoxide and hydrogen gas.

3. Oxidation with Chromic anhydride \(\left( {{\rm{Cr}}{{\rm{O}}_{\rm{3}}}} \right){\rm{.}}\)

4. Oxidation with alkaline \({\rm{KMn}}{{\rm{O}}_4}\)

5. Oxidation with acidified Potassium dichromate (identification test of alcohols): Orange colour of \({{\rm{K}}_2}{\rm{C}}{{\rm{r}}_2}{{\rm{O}}_7}\) changes to green as Ethanol is oxidised to ethanoic acid.

6. Esterification: It is the process in which a fruity smelling compound called ester is formed by the reaction of alcohol with a carboxylic acid in the presence of conc. \({{\rm{H}}_{\rm{2}}}{\rm{S}}{{\rm{O}}_{\rm{4}}}{\rm{.}}\) Esters are used in ice creams, cold drinks and perfumes.

7. Combustion: Ethanol catches fire quickly and burns with a blue flame in the presence of oxygen.

What is Ethanol Used in?

1. As an Ingredient in Alcoholic Beverages

Ethanol (or ethyl alcohol) is the most common type of alcohol that is consumed by over two billion people every day. It is produced by the fermentation of sugars and starches. Though it is consumed to change the way one feels for centuries, its overconsumption greatly affects the human body. It damages liver, impairs cognitive and motor functions and acts as a central nervous system (CNS) depressant.

2. To Produce Methylated Spirit (meth)

Denaturing ethanol is usually done to discourage the overconsumption of alcohol. This is done by mixing ethanol with methanol. Denatured ethanol is also called methylated spirit, which is poisonous and makes ethanol unfit for consumption.

Methylated spirit is combustible; hence it can be used in lamps and stoves made for camping. It is also used as a component of household cleaning products, usually glass cleaners.

3. As a Solvent

Ethanol is used as a solvent to dissolve many organic compounds that are insoluble in water. It is used in perfumes, cosmetics, paints, detergents and inks.

Ethanol’s anti-bacterial properties inhibit the growth of micro-organisms (germs). It is a major component in hand sanitisers and hand wipes.

4. Used as a Fuel

Ethanol undergoes complete combustion, hence it acts as a clean fuel. It does not contribute much to pollution as it burns with a clean, smokeless flame to produce carbon dioxide and water.

\(2{{\rm{C}}_2}{{\rm{H}}_5}{\rm{OH}} + 6{{\rm{O}}_2} \to 6{{\rm{H}}_2}{\rm{O}} + 4{\rm{C}}{{\rm{O}}_2}\)

Ethanol is usually mixed with the gasoline to produce ‘gasohol”, which is about 10-20% ethanol.

Summary

Among all alcohols, Ethanol holds a special place in our day to day lives. From perfumes and sanitisers to drinks and fuel, it covers a wide range of applications. Hence, it is important to learn about its formula and structural properties. In this article, we learnt about Ethanol, beginning from its structure, moving towards its preparation to its uses.  We also learnt about its basic physical and chemical properties.

FAQs on Ethanol Formula

Here are some FAQs on Ethanol formula:

Q1: Is alcohol the same as Ethanol?
A1: Alcohols are organic molecules assembled from carbon \(\left( {\rm{C}} \right){\rm{,}}\) oxygen \(\left( {\rm{O}} \right){\rm{,}}\) and hydrogen \(\left( {\rm{C}} \right)\) atoms. Ethanol is a two carbons alcohol (also known as ethyl alcohol). It is the form of alcohol contained in beverages, including beer, wine, and liquor.

Q2: Is Ethanol the alcohol we drink?
A2: The type of alcohol in the alcoholic drinks we drink is a chemical called ethanol. To make alcohol, you need to put grains, fruits or vegetables through a process called fermentation (when yeast or bacteria react with the sugars in food – the by-products are ethanol and carbon dioxide).

Q3: What is \({{\rm{C}}_2}{{\rm{H}}_6}{\rm{O}}\)?
A3: \({{\rm{C}}_2}{{\rm{H}}_6}{\rm{O}}\) is the condensed formula of ethanol or ethyl alcohol. The chemical formula can also be written as \({\rm{C}}{{\rm{H}}_3}{\rm{C}}{{\rm{H}}_2}{\rm{OH}}\) or \({{\rm{C}}_2}{{\rm{H}}_5}{\rm{OH}}\)

Q4: Which is better, ethanol or isopropyl alcohol?
A4: Ethanol is often used at concentrations of 70% because higher concentrations evaporate too quickly, and lower concentrations aren’t as effective, which doesn’t happen with isopropyl alcohol (IPA).

Q5: What is \(95\% \) ethyl alcohol used for?
A5: \(95\% \) ethanol is mainly used as an analytical solvent. It is also used as a disinfectant in many lab applications when diluted to \(70\% .\) It is Denatured ethyl alcohol. This chemical is designed for lab or educational use only – not for food, drug, or home use.

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