What is a solvent?
In everyday life, all mankind uses solvents every day. Some may disagree with this statement, insisting that all these are special compounds capable of dissolving various substances, and people use them only from time to time as necessary.
In some ways these dissenters will be right, the solvents are really chemical organic and inorganic compounds that are functionally capable of dissolving the most diverse substances. But the most famous and widespread type of such substances is water, which humanity uses daily in the process of vital activity, and which covers 70% of the surface of our planet.
And thousands of scientists around the world are trying to find life in the universe, based on the availability of water on a particular planet. Agree, it sounds strange enough - the basis of life on the planet is the solvent.
Like all chemical compounds, this class can be divided into organic and inorganic. If to classify them according to their physical properties, they are low-boiling( t boiling below 100 ° C) and high-boiling( t boiling above 150 ° C).They are also distinguished by the degree of volatility: volatile, medium volatile, and volatile. Depending on the degree of viscosity, these compounds are low viscosity, medium viscosity, and also highly viscous.
In addition, substances are considered for the presence / absence of a dipole moment, as well as on the magnitude of the dielectric constant. In accordance with these indicators, there are polar and non-polar solvents .
Polar and nonpolar solvents - consider the nature of
substances. Polar solvents are chemical compounds whose molecule is a dipole. All polar representatives in their molecule have donor atoms, but they are subdivided into mobile protons or protons( water, carboxylic acids, amines), and also not containing such protons, otherwise called aprotic( ketones, ethers, as well as tertiary amines).
The advantages of polar solvents include:
- ability to form hydrogen bonds;
- content of acid proton;
- ability to stabilize ions: cations - due to an unshared pair of electrons;anions - due to the obtained hydrogen bonds.
- high dielectric constant;
- ability to dissolve various polar organic substances;
- wide temperature limits of the liquid state.
The most famous and frequently used representatives of this class are water, methyl alcohol, glycerin.
Non-polar substances are compounds whose molecule is not a dipole. They do not dissolve salts and bases, often in reactions protruding with nucleotide reagents. Therefore, in such cases, these solvents are rarely used. They also have a low boiling point, which does not allow them to be used in reactions with thermal excitation of molecules.
Non-polar mixtures perfectly dissolve nonpolar gas molecules. This property is widely used to produce compressed gases, the structure of which is extremely unstable and dangerous, but in the dissolved state they are perfectly transported and stored in steel cylinders. The most famous solvents of this class are acetone, white spirit, benzene.
Applications of solvents
From the above, it can be concluded that the polarity of solvents plays a very important role in determining their properties. There is an unspoken rule for the use of these solvents: "like dissolves in like", which very accurately characterizes their field of application.
Hydrocarbon solvents( non-polar) are widely used in the paint and varnish industry, due to their low cost, as well as wide availability. They are obtained when distilling shale gasoline, oil gas, oil, coal.
Ketones( polar) are also used in the paint industry, due to their high solubility and relatively low toxicity. Esters are the most common type of organic solvents for action on polymers, in the paint and varnish industry, in medicine.
Alcohols are used in the form of a process solvent, surface cleaner, in the production of consumer products, aerosol solvents, etc.
Almost all organic solvents are toxic and have a harmful effect on humans. When working with them, you must strictly adhere to security measures. Premises where works are performed should be well ventilated, and the necessary manipulations themselves should be carried out in gloves and respirators.
It is also necessary to take into account the exceptional fire hazard of these connections. Therefore, where these components are stored, fire safety rules must be observed.