Organic Solvents

From the labs of famous pharmaceuticals to the shelves of your neighbourhood hardware store, organic solvents are everywhere, working quietly in the background to dissolve, extract, and purify. These carbon-based liquids form the backbone of numerous chemical industries, enabling them to produce a wide range of products, from lifesaving medicines to high-gloss paints. But what are organic solvents? Why are they so special, and what properties do they hold? In this guide, we will answer all these questions, along with understanding their types and uses. 

1.0Definition of Organic Solvents 

Organic solvents are liquids containing carbon that can dissolve other substances, primarily those that are non-polar or weakly polar. In other words, they are the chemical compounds composed mostly of carbon atoms used to dissolve, suspend, or extract other substances, commonly organic compounds. Most importantly, organic compounds do this all, without causing a chemical change in either the solvent or the dissolved material. A few common examples of organic solvents are benzene, toluene, xylene, etc. 

2.0Characteristics of Organic Solvents 

Organic solvents possess a number of vital properties. Understanding these properties of organic solvents helps to understand the types and usage of these solvents. These properties or characteristics are: 

• Volatile: Volatility means the ability of a substance to evaporate at room temperature. Almost every organic solvent is highly volatile. 
• Flammable: The Ability to quickly catch fire is known as flammability. A large number of organic solvents are highly flammable, making them difficult to handle and store. 
• Solubility: A solvent can dissolve other chemical substances into itself. In the case of organic solvents, these are highly soluble. 
• Boiling points: Organic solvents have a low boiling point, which helps in easy removal from a system of reactions through evaporation. 
• Miscibility: It is the ability of various chemical substances to mix with water. Some organic substances, like ethanol, are highly miscible, while others, like hexane, are immiscible. 
• Polarity of organic solvent: polarity describes the division of electric charge inside a molecule or bond, such that there exists a positive and negative end. The polarity of organic solvents varies across different solvents. For instance, hexane is non-polar, while ethanol is polar to some extent. 

3.0Types of Organic Solvents

Organic solvents are broadly divided into various categories based on their functional group, chemical structure, and polarity. Here are the three major types of organic solvents:

Hydrocarbon Solvents 

As the name suggests, hydrocarbon solvents are mainly composed of carbon and hydrogen atoms. These solvents are non-polar, hence, are used to dissolve non-polar substances such as oils, waxes, fats, and greases. These solvents are further divided into: 

1. Aliphatic Hydrocarbon Solvents: These hydrocarbon solvents have very low polarity, boiling points, and are volatile and flammable, yet chemically stable. In structure, aliphatic solvents are straight-chain or branched-chain alkanes. Examples include hexane, heptane, nonane, and petroleum ether. 
2. Aromatic Hydrocarbon Solvents: These possess a strong odour, with moderate polarity, and higher solvency. These can also be flammable as well as toxic. Structurally, it contains one or more benzene rings. For example, benzene, toluene, and xylene. 

Oxygenated Solvents 

This type of organic solvent contains oxygen atoms in its molecular structure, which gives it enhanced polarity, ultimately making it suitable for dissolving both polar and non-polar compounds. These are further divided based on the type of functional group present in them:  

1. Alcohols: They contain a hydroxyl (-OH) functional group in their structure. These are miscible in water and have antibacterial and antiseptic properties. Examples include Ethanol, Methanol, Isopropanol (IPA), and Butanol. 
2. Ketones: They are identified by a carbonyl group (C=O) in their structure. These are good solvents for plastics and other synthetic fibres. Ketones are highly volatile and minimally polar. Examples include Acetone, Methyl Ethyl Ketone (MEK), Cyclohexanone, etc. 
3. Ethers: Ethers are moderately polar with a low boiling point and form explosive peroxides when stored. Structurally, these contain Two alkyl or aryl groups connected by an oxygen atom (R–O–R’). Examples of ethers include Diethyl Ether, Tetrahydrofuran (THF), Dioxane, etc. 

Halogenated Solvents 

They consist of halogen atoms (bromine, chlorine, fluorine, or iodine) attached to a ring or a hydrocarbon chain. They have high solvency potential and the capability to dissolve materials that are insoluble in oxygenated or hydrocarbon solvents. Examples of these solvents include Chloroform (CHCl₃), Carbon Tetrachloride (CCl₄), Methylene Chloride (CH₂Cl₂), and Trichloroethylene.

4.0Organic Solvents List 

Although there are a huge number of organic solvents that are used in various industries, here is the most commonly used organic solvents list:

5.0Uses of Organic Solvents

The uses of organic solvents span across different industries due to their various beneficial abilities, like dissolving or transporting other substances easily. Some practical uses of these versatile heroes are: 

• Paints and Coatings: Serve as carriers for pigments and facilitate the process of application.
• Pharmaceuticals: Applied in drug manufacturing, extraction, and purification.
• Cosmetics and Personal Care: Found in perfumes, nail polish removers, and hair sprays.
• Industrial Cleaning: Removal of grease from metal surfaces and machine parts.
• Printing: Applied in printing inks to regulate consistency and drying time.
• Extraction Processes: Necessary in obtaining essential oils, flavours, and fragrances from raw materials.
• Laboratory Practice: Central to chemical reactions, purification, and sample preparation.