Today, we use ethanol for a wide range of purposes, from producing medicine
and alcohol, synthesizing chemical products, and fueling our everyday household items
such as heaters, lamps and vehicles. Some of the oldest combustion engines ran on
ethanol, which makes ethanol history closely related with car history. Ethanol cars are
starting to be more popular than ever and the history of the relationship between ethanol
and our society goes back further than the history of our modern car filled society.
Ethanol has many different names such as ethyl alcohol, pure alcohol, grain
alcohol, or drinking alcohol. The characteristics of Ethanol are flammable, evaporative,
and colorless, and have a structural formula of CH3CH2OH. One of the earliest
biotechnologies that humans employed is Fermentation of sugars into alcohol. Humans
have used ethanol as an intoxicating ingredient that is found in alcoholic beverages for
quite a long time. The physical properties of ethanol stem primarily from the presence of
its hydroxyl group and the shortness of its carbon chain. Ethanol's hydroxyl group is able
to participate in hydrogen bonding, rendering it more viscous and less volatile than less
polar organic compounds of similar molecular weight, such as propane (Wikipedia).
Ethanol is a versatile solvent, miscible with water and with many organic
solvents, including acetic acid, acetone, benzene, carbon tetrachloride, chloroform,
diethyl ether, ethylene glycol, glycerol, nitromethane, pyridine, and toluene. It is also
miscible with light aliphatic hydrocarbons, such as pentane and hexane, and with
aliphatic chlorides such as trichloroethane and tetrachloroethylene (Wikipedia).
Ethanol is produced both as a petrochemical, through the hydration of ethylene
and, via biological processes, by fermenting sugars with yeast. Which process is more
economical depends on prevailing prices of petroleum and grain feed stocks.
Fermentation is the oldest way for humans to produce ethanol, and this is the traditional
way of making alcoholic beverages. It is also the process used for the vast majority of
ethanol fuels on the market. This is the chemical formula for turning sugar into ethanol
and carbon dioxide:
C6H12O6 → 2 CH3CH2OH + 2 CO2
C6H12O6 is simple sugar, also known as dextrose or D-glucose.
CH3CH2OH is ethanol.
CO2 is carbon dioxide.
From the formula above, one sugar molecule is turned into two ethanol molecules and
two carbon dioxide molecules. This is how to make ethanol through fermentation.
Another method of making ethanol would be through ethylene hydration. Ethanol
produced through ethylene hydration is commonly referred to as synthetic ethanol, since
it isn't the result of a biological process. Synthetic ethanol is chiefly used as a solvent and
as an industrial feedstock. Acid is normally used as a catalyst for the process.
C2H4(g) + H2O(g) → CH3CH2OH(l)
C2H4 is ethylene.
Ethanol fuel is a type of alcohol found in alcoholic beverages that is often made
from common agricultural products. It is either mass-produced by fermentation of sugars
or from cellulose. Wheat or corn kernels are ground in a hammer-mill to expose the
starch, the ground grain is then mixed with water, heated briefly and enzymes are added
to convert the starch to sugar using a chemical reaction called hydrolysis. Yeast is added
to ferment the sugars to ethanol and finally the ethanol is separated from the mixture by
distillation. The fermentation process is quite simple; a glucose molecule is broken down
into ethanol molecules and one carbon dioxide molecule, the carbon dioxide is released
into the air and you are left with a colourless, clean burning liquid with a strong odour
(Ethanol History).
Ethanol is classified as a primary alcohol, meaning that the carbon its hydroxyl
group attaches to has at least two hydrogen atoms attached to it as well. Many ethanol
reactions occur at its hydroxyl group. In the presence of acid catalysts, ethanol reacts with
carboxylic acids to produce ethyl esters and water:
RCOOH + HOCH2CH3 → RCOOCH2CH3 + H2O
Strong acid desiccants cause the dehydration of ethanol to form diethyl ether and other
byproducts. If the dehydration temperature exceeds around 160 °C (320 °F), ethylene will
be the main product. Millions of kilograms of diethyl ether are produced annually using
sulfuric acid catalyst:
2 CH3CH2OH → CH3CH2OCH2CH3 + H2O (on 120 °C)
Ethanol is a neutral molecule and the pH of a solution of ethanol in water is nearly 7.00.
Ethanol can be quantitatively converted to its conjugate base, the ethoxide ion
(CH3CH2O−), by reaction with an alkali metal such as sodium:[27]
2 CH3CH2OH + 2 Na → 2 CH3CH2ONa + H2
Ethanol is not used industrially as a precursor to ethyl halides, but the reactions are
illustrative. Ethanol reacts with hydrogen halides to produce ethyl halides such as ethyl
chloride and ethyl bromide via an SN2 reaction:
CH3CH2OH + HCl → CH3CH2Cl + H2O
There are plenty of more uses for ethanol and there still is a lot of room for
progression in the technology that works around ethanol. It may one day be a very
reliable resource that we can count on and might have a an even huger impact on the
world that it already does today.