Solvents

A solvent is a substance, that becomes a solution by dissolving a solid, liquid, or gaseous solute. Most solvents are organic (carbon-containing) chemicals.

These are called organic solvents and are usually clear and colourless liquids and many have a characteristic smell. They usually have a low boiling point and can be removed easy by distillation, leaving the dissolved substance behind. Solvents should not react chemically with the dissolved compounds.

The concentration of a solution is the amount of compound that is dissolved in a certain volume of solvent. The solubility is the maximum amount of compound that is soluble in a certain volume of solvent at a specified temperature.

Solvents fall into one of two categories: polar (hydrophilic) or non-polar (hydrophobic/lipophilic). A hydrophile is a molecule or other molecular entity that is attracted to water molecules and tends to be dissolved by water. In contrast, hydrophobes are not attracted to water and may seem to be repelled by it.

Polarity describes the electrical charge the molecules carry. Compounds that share elections equally are non-polar,and those that share unequally are polar. The polarity an important part of extracting undesirable compounds and material from your extracts. The terpenes and cannabinoids in cannabis are essentially oils. Oil is non-polar while water is polar and the two repel each other. These two fluids don’t mix because of their different polarity.

Non-polar solvents, like propane and butane, dissolve the non-polar compounds like lipids, oils, and waxes. Polar solvents, like ethanol and acetone extract polar compounds. Water insoluble molecules, like chlorophyll, are soluble in alcohols like ethanol.

Protic solvents - Protic solvents can participate in hydrogen bonding, which is a powerful inter molecular force. Additionally, these O-H or N-H bonds can serve as a source of protons (H+).

Aprotic solvents - may have hydrogen's on them somewhere, but they lack O-H or N-H bonds, and therefore cannot hydrogen bond with themselves.

Some solvents are effective at dissolving the solute but are expensive or hazardous to health and the environment. Comparisons can be made by comparing numbers in the table. For example, acetonitrile is much more polar than acetone but exhibits slightly less hydrogen bonding, but is not recommended for extraction.

For extraction we would use acetone (UN1090) which is the lowest boiling point (56.05°C) and is a polar protic solvent. If available we would use CO2 which is a very good solvent but it also removes the waxes from the plant material and needs winterization to remove them.

Isopropyl alcohol has a higher boiling point (82°C) and is less polar than acetone, and more expensive than acetone. It also pulls more waxes, lipids and fats from the raw product which has to be removed by winterization. When winterized an isopropyl extraction produces a large amount for yellow wax and can clog filters very quickly when filtering.

When winterizing we need to bond to the fats and lipids and waxes so we would use ethanol which is a polar aprotic solvent with a high value and is environmentally safe.

The table shows that the "polar" molecules have higher levels of polar bonding and the protic solvents have higher levels of hydrogen bonding.

*Boiling points - are measurements for 1 atmosphere - air pressure at sea level

https://en.wikipedia.org/wiki/Solvent