Isopropyl alcohol (propanol-2, isopropanol, i-propanol, isopropyl alcohol) is a chemical compound widely used due to its dissolving ability, disinfecting and preserving properties. This alcohol is used in many industries, as well as motorists and doctors.
Isopropyl alcohol - what is it?
Isopropyl alcohol is a secondary monohydroxy alcohol. The chemical formula of isopropanol is CH 3 - CH (OH) - CH 3 . Isopropanol can be considered as a derivative of the saturated hydrocarbon propane CH 3 - CH 2 - CH 3 , in the molecule of which one hydrogen atom is replaced by an alcohol - hydroxyl group (-OH). Since the hydroxyl group in the molecule is one, the alcohol is called monoatomic. As can be seen from the chemical formula of isopropyl alcohol, the carbon bound to the hydroxyl group is connected to two CH 3 groups. Therefore, alcohol is called secondary.
The structural formula of isopropyl alcohol, as well as the formulas of some other monohydric alcohols are shown in the figure.
Physical properties
Many properties of isopropanol, boiling point, for example, are due to the presence of an alcohol group (-OH). This group has a high polarity. As a result, the –OH group of one isopropanol molecule forms a bond with the –OH group of another isopropanol molecule. Thus, the molecules are associated, that is, are interconnected. This bond is called hydrogen. It is weak, but is of great importance in nature.
Due to hydrogen bonds, water H 2 O under ordinary conditions is a liquid, not a gas, such as, for example, a similar in structure substance H 2 S hydrogen sulfide. It is the presence of hydrogen bonds that leads to the fact that the solid phase of water - ice - has a lower density in nature than the liquid phase, as a result of which the ice does not sink.
The formation of hydrogen bonds explains the high boiling point of isopropyl alcohol and other low molecular weight alcohols in comparison with compounds of a similar structure. For example, the boiling point of propane is -42 ° C, that is, propane at any temperature above -42 ° C is in a gaseous state. The boiling point of isopropyl alcohol is much higher and is 82.4 ° C. This means that isopropanol is in a liquid state at ordinary temperature.
If we compare the boiling point of isopropyl alcohol and methyl alcohol, the first one is slightly higher: 82 degrees against 65. This means that under normal conditions, isopropyl alcohol evaporates less than methyl alcohol.
The melting point and boiling point of isopropyl alcohol and some other compounds are presented in the table.
| Substance | Boiling point, | Melting point, o C |
| Methanol | 65 | -98 |
| Ethanol | 78 | -117 |
| Propanol | 97 | -127 |
| Isopropanol | 82 | -88 |
| Propane | -42 | -190 |
The formation of hydrogen bonds between the alcohol groups of isopropanol and water molecules causes the solubility of this alcohol in water. Solubility depends on the number of carbon atoms in the chain, the less they are, the better the alcohol is dissolved. Therefore, among the alcohols, methanol, which can be mixed with water in any ratio, has the highest solubility in water. Ethanol is soluble in water slightly worse than methanol, and isopropanol is worse than ethanol.
Main characteristics of isopropyl alcohol
It is soluble in acetone, soluble in benzene, miscible with water, ether, ethanol.
Density 0.7851 g / cm 3 (20 ° C).
The lower explosive limit is 2.5% (by volume).
Melting point -89.5 ° C.
Boiling point + 82.4 ° .
The pressure dependence of the boiling point of isopropyl alcohol is presented in the table.
| Vapor pressure, mmHg | Boiling point, |
| 1 | -26.1 |
| 10 | 2,4 |
| 40 | 23.8 |
| 100 | 39.5 |
| 400 | 67.8 |
| 1020.7 | 90 |
Chemical properties
Isopropyl alcohol is a colorless liquid. It has a characteristic odor, not like the smell of ethyl alcohol. Does not conduct electric current.
It enters into numerous chemical reactions that are used for industrial syntheses. Most of the isopropyl alcohol produced goes to acetone production. To obtain acetone, isopropanol must be oxidized with a strong oxidizing agent - a mixture of K 2 Cr 2 O 7 + H 2 SO 4 or KMnO 4 + H 2 SO 4 .
Getting
In Russia, about 40 thousand tons of isopropyl alcohol were produced in 2017, almost 20% less than in 2016. The production volume is quite small - almost 4 million tons were produced during the same methanol period.
Two enterprises produce isopropyl alcohol in Russia: CJSC Synthetic Alcohol Plant in the city of Orsk, Orenburg Region, and Synthesis Acetone LLC in the city of Dzerzhinsk, Nizhny Novgorod Region.
In Orsk, isopropanol is produced by the method of sulfuric acid hydration of propylene or propane-propylene fraction obtained from thermal or catalytic cracking gases. Two types of isopropanol are obtained, which differ in the degree of purification: technical (87%) and absolute (99.95%). In Dzerzhinsk, isopropanol is obtained by hydrogenation of acetone.
By-product in the production of isopropyl alcohol by hydration of propylene is diisopropyl alcohol, which is of particular value as a substance having a high octane number of 98.
Application
Isopropyl alcohol is an excellent solvent, so it has a wide scope. It is used mainly in the chemical industry, as well as in the oil refining, wood-chemical, furniture, medical, food, and perfume industries, in the printing industry, and in the household. Directions for use:
- solvent,
- preservative
- dehydrating agent
- extractant of impurities
- stabilizer,
- defroster.
The use of isopropanol in the chemical and automotive industries
Application in the chemical industry is as follows:
- raw materials for the production of acetone,
- production of plastics - low pressure polyethylene and polypropylene,
- synthesis of isopropyl acetate
- insecticide production
- solvent in the production of ethyl cellulose, cellulose acetate, nitrocellulose in the paint and varnish industry,
- safe transportation of nitrocellulose (30% isopropanol is added to it),
- extractant in fine chemical technology.
- Application in the oil refining industry:
- urea solvent used for dewaxing diesel fuel,
- additive to oils, enhancing their anti-corrosion properties and lowering pour point,
- "Removal" of water from gasoline tanks.
Water enters the fuel lines and tanks of oil depots by condensation from moist air. At low temperatures, it freezes and can form an ice plug. When absolute isopropanol is added, water dissolves in it and does not freeze.
In the automotive industry:
- "Removal" of water from gas tanks by dissolving it,
- as a fuel component to increase octane and reduce toxic emissions,
- windshield defroster,
- antifreeze for radiators,
- removal of brake fluid from hydraulic brake systems.
The use of isopropanol in other types of economic activity
Application in furniture and wood chemical industry:
- extraction of resins from wood mixed with other solvents,
- removal of old varnish, solvent of French polishing, glues, oils,
- binder in polishes and cleaners.
In printing, isopropanol is used for wetting in printing processes. In electronics - as a solvent for cleaning contact sockets, magnetic tapes, disk heads, laser lenses, for removing thermal paste, cleaning keyboards, LCD monitors, glass screens. You can not use it only for cleaning vinyl, since isopropanol reacts with it.
Application in the medical industry and medicine:
- part of antiseptic solutions, impregnating liquid for napkins,
- a disinfectant to wipe the injection site,
- 75% aqueous solution is used as a hand sanitizer,
- disinfectant swabs
- desiccant for the prevention of otitis media,
- a preservative to preserve genetic material and analyzes (less toxic than formaldehyde).
Isopropanol has advantages over ethanol: a more pronounced antiseptic effect and low price. Therefore, in cases where ethanol was previously used, isopropanol is now used.
In the cosmetic and perfumery industries, isopropanol is used in the production of:
- cosmetics
- personal hygiene products
- perfumes, colognes, varnishes.
In the food industry, isopropanol is used in the production of frozen foods as a coolant.
In the household:
- for cleaning various surfaces except rubber and vinyl,
- to remove stains from fabrics, wood,
- for removing glue from stickers (does not act on paper isopropanol).
Toxicity
Isopropanol is used in medicine as a local antiseptic. When used locally, it evaporates quickly and does not have a negative effect.
If inhaled, it irritates the airways and can cause a headache. A high concentration of isopropanol in the air slows down the central nervous system, leading to loss of consciousness. Therefore, you can work with isopropanol only in a well-ventilated area.
Inside isopropanol is not used because it is toxic. Once in the liver, it turns into a poisonous substance - acetone, which affects the liver, kidneys and brain. 200 ml of isopropanol are a lethal dose.