Everyday chemicals- Ethanol
A Public Service Announcement- by Paul C
What is Ethanol?
Ethanol is a chemical that, whether we know it or not, plays a role in the lives of most of society on a day-to-day basis.
It is a liquid at room temperature, and is also referred to as ethyl alcohol. It is clear and has a mild odour similar to that of wine or whiskey. It’s chemical formula is C2-H6-O, meaning that it is a molecule formed by covalent (molecular) bonds between Carbon, Hydrogen, and Oxygen atoms.
Combustion: as ethanol is composed of Caron, Hydrogen, and Oxygen, it can react with Oxygen to form water and carbon dioxide. This is why it can be used as a biofuel in certain combustion engines.
C2H60 + 3O2 => 2CO2 + 3H2O
Ethanol reacts with sodium at room temperature to form Sodium ethoxide.
2C2H6O + 2Na => 2C2H5ONa + H2(g)
Ethanol also is able to react in other ways, such as Oxidation, Dehydration, Dehydrogenation, Esterification, and Halogenation (with certain compounds).
Compound Type (Structure)
Ethanol is held together by covalent bonds, meaning that the sharing of electrons between the bonded atoms holds the molecule together. As a covalent compound, ethanol bonds differently than ionic compounds do, because there are no total charge changes. However, in the bonds that make up ethanol (C-O, C-H, and O-H) the atoms have differing attractive forces on the shared electrons in their respective covalent bonds.
Because of certain atoms having stronger or weaker attraction to the shared electrons, partial charges are determined between both atoms, with the atom that has a stronger attractive force being partially negative, and the one with the weaker force being partially positive. This force is listed as a numeric value for each element on the periodic table, and it is known as electronegativity (EN).
The difference in electronegativity values (∆EN) determines whether the forces between atoms are small enough to omit (0-0.5), creating a “pure”, or nonpolar covalent bond, whether the forces are larger enough to create partial charges between electron sharing (0.5-1.7), creating what is called a polar covalent bond, or whether one atom has so much stronger of an EN value that it will simply take the electron as opposed to sharing it, forming an ionic bond.
Polar covalent bonds create opposite partially charged positive and negative poles between two bonded atoms depending on which atom has the higher EN.
The type of covalent bond is one of the factors that contribute to determining the polarity of the molecule as a whole. Both types of covalent bonds are present in ethanol. The C-H bonds are nonpolar covalent, as the atoms are of similar electronegativity (lower ∆EN), and the C-O and O-H bonds are polar covalent since O is significantly higher in electronegativity than C or H. Because of this, there is a slight positive charge on the C and H attracted to the O, with the O having a slight negative charge.
To Conclude With Molecular Polarity...
With 4 pairs (8 electrons), and 4 atoms attached to each C, the geometric shape of that part of the atom is tetrahedral, which would generally mean that the molecule would be nonpolar (due to no partial charge di-poles), but in this case, the tetrahedral shape is only part of the molecule as a whole. The atoms around the O, however, are only 2 (C and H), and create a bent shape. This geometry, combined with the fact that O has the highest electronegativity of the three elements in the compound shows that there is a slight charge separation, creating a di-pole within the molecule. This means that Ethanol is a polar molecule. (see below)
Structure and Properties
As stated in the physical properties, ethanol is in liquid state at room temperature due to the fact that molecular compounds have very low melting points due to the fact that intermolecular forces between ethanol are weak enough to force the compound into liquid state at room temperature. Ethanol is very hydroscopic as well. This is due to the fact that ethanol bonds with water and other ethanol via hydrogen bonding. Although hydrogen bonding is still an intermolecular force, it is the strongest form of intermolecular force, due to the fact that Hydrogen and Oxygen form strong partial positive and negative charges respectively when bonding. (Note: hydrogen bonding will only occur when Hydrogen would carry the partial positive charge, and either Fluorine, Oxygen, or Nitrogen carrying the partial negative charge). Due to the fact that ethanol is able to attract other ethanol through hydrogen bonding, it has a relatively high boiling point with respect to molecular compounds, as the hydrogen bonding is the most powerful intermolecular force.
Note: The nonpolar ends of ethanol (ends without partial charges) are able to attract other nonpolar molecules such as those found in gasoline and other fuel via dispersion forces (the weakest form of intermolecular force)
Ethanol is a renewable fuel additive that can help reduce imported oil and greenhouse gas emissions. It has lower CO2 emissions when used as a fuel (combustion reaction) in comparison to petroleum. On a life-cycle analysis, the production of corn-based and cellulosic production of ethanol was proven to also potentially reduce greenhouse has emissions. Ethanol production also has the ability of creating jobs in rural areas where employment opportunities are needed. An example of this was displayed in 2012, where ethanol production added more than 365,000 jobs across the United States. Below is the economic impact of the ethanol industry in the United States in 2010.
Costs to Human Health
Ethanol is classified as causing cancer in humans following ingestion. There are multiple ways in which ethanol may cause cancer.
One of the ways in which ethanol may cause cancer is through converting into acetaldehyde (see left), which is a toxic chemical that ethanol (alcohol) is converted to once in our bodies. It may cause cancer by damaging DNA and preventing cells from repairing the damage. Acetaldehyde causes liver cells to grow faster than normal. The new cells have an increased likeliness to be subject to gene changes possibly leading to cancer. Although mainly broken down by the liver, some bacteria throughout our mouth and digestive organs are able to convert ethanol into acetaldehyde as well.
Ethanol is highly flammable and reacts violently with strong oxidizing agents. Ethanol vapour mixes with air to create explosive mixtures as well. Ethanol fires should be resolved with alcohol resistant foam and a standard fire with a breathing apparatus. It is toxic upon ingestion, and symptoms vary based on severity. Dermal and ocular exposure causes burning and stinging. Ethanol should also not be released into the environment.
The best way to be safe from every-day bodily harm from ethanol would be to avoid drinking alcohol all together, but as long as one drinks responsibly and in moderation, there should not be an issue. Also, a healthy dose of common sense would be of use when it comes to other ethanol mixtures: do not ingest them!
With regards to alternatives to ethanol the ideas usually take steps backwards. Being very prominent in the fuel industry, ethanol or ethanol-fuel mixtures are being brought forth as the potential alternatives. Essentially, the alternative to the alternative would be the standard: petroleum and other high-emission fuels.
3. College of Saint Benedict & Saint John's University. http://employees.csbsju.edu/hjakubowski/classes/Chem%20and%20Society/Alcohol_Drugs/olEtOHStructAct.htm (July 9, 2014)
4. University College Cork http://www.ucc.ie/academic/chem/dolchem/html/comp/ethanol.html
(July 9, 2014)
5. U.S. Department of Energy.
http://www.afdc.energy.gov/fuels/ethanol_benefits.html (July 9, 2014)
6. Cancer Research UK. http://www.cancerresearchuk.org/cancer-info/healthyliving/alcohol/howdoesalcoholcausecancer/how-does-alcohol-cause-cancer (July 9, 2014)