Description

Organic solvents are chemicals that have a carbon-based molecular structure. They are used to dissolve a material to create a solution, or to extract one material from another.

Organic solvents can be categorized into natural and synthetic solvents. Natural solvents are those that can be produced by living organisms. Synthetic solvents are those that require chemical reactions of other compounds in order to be produced.

Types of Organic Solvents

Organic solvents can be classified based on their structure and functional groups. They may be divided into aromatic hydrocarbons, aliphatic (non-aromatic) hydrocarbons, and carbon compounds with various functional groups including carbonyls, alcohols, ethers, and halocarbons.

The GlobalSpec SpecSearch database contains these types of organic solvents.

• Aliphatics including alkenes. They are nonpolar solvents. Some applications include oil extraction, dye, paint, pharmaceuticals, adhesives, and polymerization.
• Aromatics which are generally nonpolar solvents used as industrial solvents for paints, adhesives, printing inks, extraction, degreasing, and insecticides.
• Carbonyls including esters. They are more polar solvents used in nail varnish removers, circuit board and electronics cleaners, decaffeination, paint diluent and activation, glue, and food flavoring.
• Other functional groups including alcohols. These have varied polarity and are seen in health and beauty consumer products, dyes, oils, resins, and lubricants and are used to dissolve soaps, sugars, and certain pharmaceutical drugs.

Material Properties

Organic solvents exhibit a variety of important chemical and physical properties. Thermal properties include the freezing point, boiling point, and flash point of the solvent. Physical properties of most importance include state of matter, viscosity, vapor pressure, purity, and concentration.  The most important chemical properties of solvents are pH and polarity.

An important factor to consider when analyzing solvents is the operating temperature, i.e. the temperature at which the solvent will be used to dissolve its target material(s). As operating temperature increases, the amount of solute (material) that a solvent can dissolve per unit volume increases, raising its dissolving capacity.

Polarity and Intermolecular Forces

Polarity and the intermolecular forces surrounding it are essential to categorizing solvents. A solvent’s polarity determines its compatibility with a target material and largely influences its dissolving effectiveness. Polarity is the separation of electric charge in a molecule.

A compound that has an uneven distribution of charge due to intermolecular forces is said to have a dipole moment and is considered polar. Solvents tend to dissolve materials of similar polarity (“like dissolves like”). A very nonpolar aliphatic such as hexane can readily dissolve many oils, waxes, and other nonpolar materials. Some compounds such as acetone have both polar and nonpolar properties and dissolve some polar and nonpolar substances. Other intermolecular forces such as hydrogen bonding and polarizability are factors that determine how solvents and materials interact with each other.

Consumer and Commercial Applications

Organic solvents have use in many different areas. They are used as components of many types of coatings and polishes, as paint thinners and removers, as cleaning and dry cleaning agents, as nail polish remover, as industrial and consumer degreasers, in detergents, in perfumes, and in various chemical syntheses.

References

CDC — Organic Solvents — NIOSH Workplace Safety and Health Topic