Alcohols

Alcohols are compounds with the general formula R – OH, where R represents an alkyl or substituted alkyl group. Therefore, alcohols are alkane derivatives in which one or more hydrogen atoms are substituted by -OH. Alcohols are extremely valuable industrial compounds. In its rectified spirit form, ethanol is commonly employed as an antiseptic. It serves as a solvent for lacquers and varnishes and is the primary ingredient in alcoholic beverages.

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Preparation of Alcohols

Alcohol can be produced through both conventional and industrial procedures.

Preparation from Haloalkanes

When heated with aqueous alkali or wet silver oxide, haloalkanes produce the equivalent monohydric alcohols.

By Fermentation of Carbohydrates

Alcohol is produced via the slow degradation of big organic molecules (carbohydrates, sugar, and starch) in the presence of appropriate enzymes. Using this process, ethanol can be produced by fermenting glucose.

Properties of Alcohols

Alcohols get their physical and chemical features principally from the presence of a hydroxyl group.

Physical Properties of Alcohols

• Alcohols are normally liquid at room temperature.
• In general, they have greater boiling points than other hydrocarbons with the same molecular mass. In general, the alcohol’s boiling point rises as the number of carbon atoms in the aliphatic carbon chain increases.
• They are soluble in water. The solubility of alcohols with shorter hydrocarbon chains is exceptional. The solubility in water diminishes as the hydrocarbon chain length grows.
• Alcohols react with active metals such as sodium, potassium, etc., demonstrating their acidic character. The polarity of the bond between the hydrogen and oxygen atoms in the hydroxyl group is responsible for the acidic nature.

Chemical Properties of Alcohols

Due to the cleavage of the C-O bond and the O-H bond, alcohols undergo a variety of spontaneous chemical reactions. Among the most important chemical reactions of alcohol are:

Oxidation Reaction – In the presence of an oxidizing agent, alcohols are oxidised to form aldehydes and ketones, which can be further oxidized to produce carboxylic acids.

Reaction with metals – Alcohols react with active metals like sodium, potassium, etc. to generate the equivalent alkoxide.

Dehydration of Alcohols – Alcohols dehydrate when exposed to an acidic media, resulting in the creation of an alkene.

Esterification — When alcohol interacts with a carboxylic acid in the presence of a catalyst, a sweet-smelling molecule known as an ester is produced.

Classification of Alcohols

Alcohols can be divided into the following categories:

1. According to the amount of -OH groups present in the molecule.
2. Based on the type of carbon atom that bonds with the -OH group.

Classification of Alcohols on the basis of -OH groups

Monohydric alcohols: These have one -OH group in their molecules. For instance, ethanol.

Dihydric alcohols — These are alcohols whose molecules contain two -OH groups. For instance, 1,2-Ethanol.

Trihydric alcohols — These molecules contain three -OH groups. For example- 1,2,3-Propantriol.

Polyhydric alcohols are alcohols whose molecules contain four or more OH groups.

Classification of Alcohols on the basis of the nature of the carbon atom bonded to the -OH group

Based on the amount of carbon atoms directly linked to the carbon bound with the -OH group, alcohols are divided into three categories: primary, secondary, and tertiary.

Primary Alcohols – The -OH group is bonded to only one carbon atom on the carbon atom containing the -OH group.

Secondary Alcohols – The -OH group is connected to two carbon atoms.

Tertiary Alcohols – The carbon atom with the -OH group is bound to three carbon atoms.

Nomenclature of Alcohols

Alcohols are chemical compounds that have a functional hydroxyl or –OH group covalently linked to carbon. Alcohol is named from the hydrocarbon that it is generated from.

There are three ways to name alcoholic beverages:

1. Standard or trivial system
2. IUPAC system 
3. Carbinol system

Trivial or Common System

Adding the term alcohol after the alkyl group results in the common name for alcohol. Alternately, the common name of alcohol can be derived by substituting the -ane at the end of the parent hydrocarbon with the letter yl and then appending the word alcohol.

For alcohols having three or more carbon atoms, the -OH group can exist in many places. These alcohols are categorised as main, secondary, and tertiary. They are frequently designated by the prefixes n or iso-.

• The dihydric alcohols are termed glycols. The names originate from the respective alkene.
• Trihydric alcohols are typically referred to by names derived from their origin.

IUPAC System

In this approach, the name of alcohol is derived by adding the suffix ‘ol’ to the last letter of the name of the parent alkane, akene, or alkyne. However, higher and branched-chain compounds adhere to certain protocols.

Uses of Alcohols

• Ethanol is the alcohol found in alcoholic beverages.
• Alcohol is a high-performance fuel. Carbon dioxide and water are produced during combustion.
• Also used to produce vinegar.
• It is utilised as an antibacterial, a wound dressing, and an antivenin for snake bites. Also employed as a mild sedative.
• Most cough syrups contain alcohol, which is a popular element in cough medicines.
• Alcohol is utilised in disinfectants due to its antifungal and antibacterial qualities.
• In hospitals, medical facilities, and laboratories, alcohol is utilised as a cleaning agent to eradicate microbiological contamination.
• Ethanol, Methanol, and Isopropanol are solvents utilised in analytical chemistry procedures, including chromatography analysis.

Methanol, ethanol, propanol, and butanol are some regularly employed alcohols.

Read More: Uses of Methanol and Ethanol

Frequently Asked Questions on Alcohol