Isopropyl alcohol (2-propanol, isopropanol, i-propanol, isopropyl alcohol) is a chemical compound that has become widespread due to its dissolving ability, disinfectant and preservative properties. This alcohol is used in many types of industry, as well as motorists and doctors.
Isopropyl alcohol - what is it?
Isopropyl alcohol is a secondary monohydric alcohol. The chemical formula of isopropanol is CH3 – CH (OH) – CH3. Isopropanol can be considered as a derivative of the saturated hydrocarbon propane CH3 – CH2 – CH3, 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 monohydric. As can be seen from the chemical formula of isopropyl alcohol, the carbon associated with the hydroxyl group is connected totwo groups CH3. 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, they are connected to each other. Such a bond is called a hydrogen bond. She is weak, but is of great importance in nature.
Due to hydrogen bonds, water H2O under normal conditions is a liquid, not a gas, like, for example, a substance similar in structure H2 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 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 at 82.4°C. This means that isopropanol at ordinary temperature is in liquid form.condition.
If we compare the boiling point of isopropyl alcohol and methyl alcohol, then the former has a slightly higher temperature: 82 degrees versus 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, oC | Melting point, oC |
| 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 determines the solubility of this alcohol in water. Solubility depends on the number of carbon atoms in the chain, the fewer of them, the better the alcohol dissolves. Therefore, among alcohols, methanol has the highest solubility in water, which can be mixed with water in any ratio. Ethanol dissolves in water slightly worse than methanol, and isopropanol is worse than ethanol.
Main characteristics of isopropyl alcohol
Soluble in acetone, soluble in benzene, miscible with water, ether, ethanol.
Density 0.7851g/cm3 (20°C).
Lower explosive limit - 2.5% (by volume).
Melting point -89.5°C.
Temperatureboiling +82, 4°С.
The dependence of the boiling point of isopropyl alcohol on pressure is presented in the table.
| Vapor pressure, mmHg | Boiling point, oC |
| 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 electricity.
Enters into numerous chemical reactions, which is used for industrial syntheses. Most of the produced isopropyl alcohol goes to the production of acetone. To obtain acetone, isopropanol must be oxidized with a strong oxidizing agent - a mixture of K2Cr2O7 + H 2SO4 or KMnO4 + H2SO 4.
Receive
In Russia, about 40 thousand tons of isopropyl alcohol were produced in 2017, almost 20% less than in 2016. The volume of production is quite small - almost 4 million tons of methanol were produced during the same period.
Isopropyl alcohol is produced in Russia by two enterprises: Synthetic Alcohol Plant CJSC in the city of Orsk, Orenburg Region, and Sintez 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, differing in the degree of purification: technical (87%) and absolute (99.95%). In Dzerzhinsk, isopropanol is obtained by hydrogenation of acetone.
A by-product in the production of isopropyl alcohol by the hydration of propylene is diisopropyl alcohol, which is of particular value as a substance with a high octane number of 98.
Application
Isopropyl alcohol is an excellent solvent, so it has a wide range of applications. It is used mainly in the chemical industry, as well as in the oil refining, wood-chemical, furniture, medical, food, perfume industries, in printing, and in the household. Application directions:
- solvent,
- preservative,
- dehydrator,
- extractant impurities,
- stabilizer,
- de-icer.
Use of isopropanol in the chemical and automotive industries
Chemical industry applications are as follows:
- raw material for the production of acetone,
- production of plastics - low density polyethylene and polypropylene,
- synthesis of isopropyl acetate,
- insecticide production,
- solvent in the production of ethyl cellulose, cellulose acetate, nitrocellulose in paint and varnishindustry,
- safe transportation of nitrocellulose (30% isopropanol is added to it),
- extractant in fine chemical technology.
- refinery application:
- Urea solvent used for dewaxing diesel fuel
- an additive to oils that enhances their anti-corrosion properties and lowers the pour point,
- “removing” water from petrol tanks.
Water enters the fuel lines and tank farms by condensation from moist air. At low temperatures, it freezes and can form an ice plug. When adding absolute isopropanol, water dissolves in it and does not freeze.
In the automotive industry:
- “removing” water from gas tanks by dissolving it,
- as a fuel component to increase octane number and reduce toxic emissions,
- windshield defroster,
- antifreeze for radiators,
- removal of brake fluid from hydraulic brake systems.
Use of isopropanol in other economic activities
Furniture and wood chemical applications:
- extraction of resins from wood mixed with other solvents,
- removal of old varnish, French polish solvent, glues, oils,
- binder in polishes and cleaners.
In the printing industry, isopropanol is used to moisten printingprocesses. In electronics - as a solvent for cleaning contact connectors, magnetic tapes, disk heads, laser lenses, for removing thermal paste, cleaning keyboards, LCD monitors, glass screens. Do not use it just to clean vinyl, as isopropanol reacts with it.
Application in the medical industry and medicine:
- included in antiseptic solutions impregnating wipe liquids,
- disinfectant for wiping the injection site,
- 75% aqueous solution used as hand sanitizer
- disinfectant swabs,
- dryer for prevention of otitis media,
- preservative for the preservation of genetic material and analysis (less toxic than formaldehyde).
Isopropanol has advantages over ethanol: a more pronounced antiseptic effect and a low price. So where ethanol used to be used, isopropanol is now used.
In the cosmetics and perfume industries, isopropanol is used in production:
- cosmetics,
- personal care products,
- perfume, cologne, lacquer.
In the food industry, isopropanol is used as a coolant in the production of frozen foods.
In the household:
- for cleaning various surfaces except rubber and vinyl,
- for removing stains from fabrics, wood,
- to remove adhesive from stickers (on paper, isopropanol is notvalid).
Toxicity
Isopropanol is used in medicine as a local antiseptic. When used topically, it evaporates quickly and has no negative effect.
Irritating to respiratory tract if inhaled vapors, may cause headache. A high concentration of isopropanol in the air inhibits the work of the central nervous system, leading to loss of consciousness. Therefore, work with isopropanol only in a well-ventilated area.
Isopropanol is not used internally 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 is a lethal dose.
