From beverages to medicines and now sanitizers, alcohol finds its importance in our day-to-day life. Alcohol is considered as old as civilization. Its evidence dates back to 7,000 to 6,600 B.C. most of which have been found in China.
Alcohols are considered as organic derivatives of water (H-OH), in which one hydrogen atom is replaced with an alkyl group (R-OH). Two of the most widely used and simplest types of alcohol are methanol (CH3-OH) and ethanol (CH3CH2-OH).
So, is alcohol a compound? Yes, alcohol is a compound that contains at least one hydroxyl (-OH) group, attached to the carbon of the parent chain. When carbon, hydrogen, and oxygen bind together by the formation of covalent bonds, they form alcohol compounds. The general formula of alcohol is CnH2n+1(OH).
Let us study how compounds are different from mixtures and why alcohol is considered a compound.
Types of Matter
Matter in this universe is anything that has mass and occupies space. It is divided into two bold categories;
1 . Pure matter consists of elements and compounds.
2 . Mixtures, which contain heterogeneous and homogeneous mixtures.
When we look at the periodic table, we see every element has its definite place. An element is the simplest complete entity that cannot be broken down into other smaller entities.
What is a Compound?
When two or more than two types of elements combine together by chemical bonds, they form a bigger entity known as a “chemical compound”. The smallest unit of any compound is known as a molecule.
Once bonded to form a compound, these elements can not be separated by any physical means. Also, these elements in a compound are present in a definite proportion at every point in time
For example, water is a compound in which each molecule is made up of two hydrogen atoms and an oxygen atom (2:1 proportion). These molecules, through intermolecular hydrogen bonding, stay together in the form of a compound.
What is a Mixture?
Mixtures are formed when two or more compounds are physically combined without the formation of chemical bonds.
This means, there is no reaction occurring between these substances and they retain their individuality. Hence, they can be separated from the mixture by physical means. Also, there is no fixed proportion of substances in a mixture.
For example, in a mixture of salt and water, salt does not react chemically with water. And even after dissolution, salt can be retrieved again by evaporation.
I have written a separate article on saltwater. Go and check out is saltwater a compound.
So now that we know the differences between a compound and mixture, try to classify these given substances:
Steel? It is a mixture
Carbon? It is an element
Blood? It is a mixture
Sodium chloride (NaCl)? It is a compound
Tin? It is an element
Glucose? It is a compound
Is Alcohol a Mixture or Compound?
Alcohol is a compound. It is formed when carbon binds covalently with oxygen and hydrogen.
Once formed, it will attain stability and it will not separate into its constituent elements after a certain amount of time by any physical means, unlike a mixture.
The constituent elements while bonding loses their individuality and alcohol exhibits a unique set of properties. The proportion of elements at any point in time remain constant.
If we say, 70% ethanol (v/v) it means, we are talking about a mixture of 70ml ethanol in 30ml water. If we say 100% ethanol, it means we are talking about the pure compound that is ethanol, not mixed with any other substance.
Structure of Alcohol
As we studied above, alcohol can be considered an organic derivative of water. In water, an oxygen atom is sp3 hybridized, with two of its four sp3 hybridized orbitals occupied by lone pairs (non-bonding pairs of electrons).
Hence, water is sp3 hybridized, V-shaped, or see-saw shaped (deviation from tetrahedral shape due to two lone pairs). The bond angle between two hydrogen atoms is 104.5°.
The structure of alcohol is exactly like that of water, except for the fact that one hydrogen of water is replaced with an alkyl group.
Since the alkyl group is bulkier than hydrogen, it repels the second hydrogen present in the bonding orbital with more power. As a result, the bond angle becomes 109°.
Bulkier is the alkyl group, more will be the bond angle between hydrogen and alkyl group. In the below figure, you can see the deviation from the water molecule.
Classification of Alcohol
Based on the carbon atom to which hydroxyl group (-OH) is attached, alcohols can be classified into;
- “primary“, if carbon is attached to one alkyl group.
- “secondary“, if carbon is attached to two alkyl groups.
- “tertiary“, if carbon is attached to three alkyl groups.
The various types of alkyl groups in alcohol can also be replaced with aryl groups.
The bond angle between bonding pairs on oxygen will be largest in the case of tertiary alcohols and aryl alcohols (>109°) because these groups are bulkier and can repel hydrogen more effectively.
Formation of Alcohol
There are many natural sources of alcohol such as grains, sugarcane, barley, potato, and fish oils. Alcohol is extracted from these natural sources by the process of fermentation.
Yeast also performs alcoholic fermentation during the process of respiration to produce energy in the form of ATP and alcohol as a by-product.
Bacterium Clostridium acetobutylicum feeds upon cellulose to produce butanol. This process is used by many industries in the bulk production of butanol.
Chemically, alcohol can be formed by reducing higher functional groups such as carbonyl compounds (aldehydes and ketones), esters, and carboxylic acids.
Oxidation of alkenes and alkynes in the presence of strong oxidizing agents also produces alcohols.
Do you know? Out of all the countries, the highest production, as well as consumption of alcohol, is observed in Russia, where a person on average consumes around 55 liters of alcohol per year.
Properties of Alcohol
Physical appearance: Alcohols are colorless, transparent liquids at room temperature, having a slightly sweet odor (except glycerol and few lower alcohols).
Flammability: Alcohols are highly flammable due to their low flashpoints and they produce a blue flame. Also, they do not produce any smoke or soot while burning.
Polarity: The presence of the hydroxyl group makes alcohol polar in nature, as the electronegativity of oxygen (E=3.5) is higher than that of hydrogen (E=2.2), which causes the formation of the dipole moment.
Hence alcohol is a “polar organic compound”.
This image shows the intermolecular hydrogen bonding and polarity in alcohol molecules.
Boiling point and melting point: As compared to the hydrocarbons of similar molecular weight, alcohols have a higher boiling point and melting point. This is due to the presence of intermolecular hydrogen bonding which is present between the hydroxyl groups of molecules of alcohol.
Solubility: Lower alcohols like methanol, ethanol, and propanol are soluble in water. But, as the bulkiness of the alkyl group increases, its solubility decreases.
Chemical properties: Alcohols exhibit two types of chemical reactions based on the cleavage of bonds. Either they undergo cleaving C-O bond (dehydration reactions, substitution reactions) or they cleave O-H bond (oxidation reactions).
Do you know? Our body takes around 2 days to excrete alcohol out of its system, while our brain takes as little as 6 minutes to react after consuming alcohol!
Uses of Alcohol
- It is used as a preservative, to store specimens in the laboratory.
- Alcohol, specifically ethanol, is used as an antiseptic and disinfectant. Spirits and sanitizers in hospitals and laboratories contain alcohol.
- Medicinal syrups for cold and cough are often prepared with alcohol as a solvent.
- Preparation of beverages like beer and whiskey requires ethanol
- Alcohol, specifically methanol is used as fuel in internal combustion engines.
- It is also used as an anti-freezing agent by adding it along in a mixture of ethylene glycol dissolved in water.
Do you know? Only ethanol is used in beverages such as beer, whiskey, wine, etc. Because it is the only alcohol we can consume without it causing much damage to the body.
All other alcohols are very harmful if consumed. They can even burn the internal tissues.
In this article, we studied how elements combine together to form chemical compounds and how compounds are different from mixtures.
We have learned that alcohol is a compound as its constituent elements are bonded by covalent bonds. We also looked into the structure, classification, and various physical and chemical properties of alcohol.
We studied various uses of alcohol and how it is an extremely important and inseparable part of many of the essential items such as sanitizers, disinfectants, cough syrups, etc.
We hope that you understand the concept of alcohol as a compound as explained in the article.