The discovery of many chemicals was not intentional, but random, during the synthesis or study of the properties of a substance. However, many of the randomly discovered substances became very important, they were used not only in chemistry, but also in medicine, industry and other fields. Just such substances are chloroform, which will be discussed later.
Title
The name of this substance has several varieties. Indeed, like all organic compounds, it obeys the laws of the general nomenclature of molecules, trivial names and names, based on the composition of the molecule.
Therefore, for chloroform, there are several variants of the name:
- carbon trichloride;
- chloroform;
- trichloromethane.
Chloroform: what is it? You can understand from the names of the compounds, but you can consider the geometric structure of the molecule.
Molecule structure
The chloroform molecule consists of three chlorine atoms and one hydrogen atom, each atom joining a central carbon. In fact, a trichloromethane molecule is a product of the radical replacement of hydrogen atoms by chlorine atoms in a methane molecule under certain conditions.
Moreover, all C-CL bonds are completely equivalent, strongly polar. The CH bond against the background of other bonds appearing in the molecule becomes even more polarized and becomes extremely vulnerable. Therefore, upon further processing of the molecule, the CH bond is easily broken and hydrogen is replaced by other atoms (for example, also chlorine with the formation of carbon tetrachloride).
Consider what chloroform looks like. The formula is: CHCL 3. The structural formula will be as follows:
Both structures reflect the chemical essence that chloroform carries. The formula shows that the molecule is stable enough and to enter into the reaction, it is necessary to apply stringent conditions.
Physical properties
The physical properties of trichloromethane can be characterized as follows:
- Under ordinary conditions (room temperature, normal atmospheric pressure 100 kPa, humidity not higher than 80%), this substance is a very odorous liquid that has no color. The smell of chloroform is quite sharp, heavy, enveloping, resembles the smell of ether. The substance tastes sweet, but you can’t try it, as it is extremely toxic.
- It does not dissolve in water, it can dissolve only in different types of organic solvents. With water, it can form low-concentration (0.23%) solutions.
- The boiling point of this compound is lower than that of water, approximately 62 0 C.
- The melting point is sharply negative, -63.5 0 .
- The density of chloroform is greater than the density of water and is 1.483 g / cm 3 .
- The strong pronounced toxic nature of the substance by its effect on the body belongs to the group of narcotic compounds.
When dissolved in water, carbon trichloride is able to form azeotropic mixtures. In this case, chloroform in the solution will be 97.5%, and water only 2.5%. The boiling point of such a solution decreases compared to that of pure trichloromethane and is 52 0 C.
Chemical properties
Like all chlorine derivatives of methane, chloroform does not exhibit chemical activity. Therefore, there are few reactions characteristic of it. For example, treatment with chlorine molecules in the process of technological production of all methane derivatives by chlorination. For this, liquid chloroform is taken, reactions proceed as a radical mechanism, require the presence of ultraviolet radiation as a prerequisite and light quanta.
CHCL 3 + CL 2 = CCL 4 + HCL
According to the reaction equation, the product is fully chlorinated methane - carbon tetrachloride. Such reactions are one way of producing carbon tetrachloride in industry.
Also, an azeotropic mixture with water, which chloroform is capable of producing, can be attributed to chemical properties. What it is? That is, one upon boiling of which the components of the solution do not undergo any changes. By boiling such a mixture cannot be divided into fractions.
Another type of reaction that chloroform can enter is the substitution of halogen atoms for other atoms or functional groups. For example, when interacting with an aqueous solution of sodium hydroxide, it forms sodium acetate:
chloroform + NaOH (aqueous solution) = sodium acetate + sodium chloride + water
In addition, a practically significant reaction is the interaction of chloroform with ammonia and potassium hydroxide (concentrated solution), since potassium cyanide is formed as a result of this interaction .
Chloroform + ammonia + potassium hydroxide = KCN + potassium chloride + water
Chloroform storage
In the light, trichloromethane decomposes to form hazardous, poisonous products:
Chloroform = phosgene + hydrochloric acid + molecular chlorine + carbonic anhydride
Therefore, the storage conditions of chloroform should be special - dark glass bottles with dense ground stoppers. The bottle itself should be kept away from sunlight.
Getting
Getting chloroform is carried out in several ways.
1. A multi-stage methane chlorination process that occurs according to a radical mechanism under the influence of ultraviolet light and high temperature. The result is not only chloroform, but also three other products: chloromethane, dichloromethane and carbon tetrachloride. The reaction is as follows:
CH 4 + CL 2 = CH 3 CL + HCL - chloromethane and hydrogen chloride are formed
CH 3 CL + CL 2 = CH 2 CL 2 + HCL - dichloromethane and hydrogen chloride are formed
CH 2 CL 2 + CL 2 = CHCL 3 + HCL - trichloromethane (chloroform) and hydrogen chloride are formed
CHCL 3 + CL 2 = CCL 4 + HCL - carbon tetrachloride and hydrogen chloride are formed
In this way, trichloromethane is synthesized in industry.
2. The interaction between bleaching lime and ethyl alcohol. This is a laboratory method.
3. Obtaining chloroform by electrolysis (electric current) on alkali metal chlorides in an atmosphere of acetone or ethyl alcohol. Also a laboratory method for producing trichloromethane.
Cleaning
After chloroform is obtained, it needs to be purified. After all, if it is used for medical purposes, then the content of impurities in it is simply unacceptable. If the purpose of the application is technical, then the content of foreign substances should be limited.
There may be different impurities that chloroform contains. What it is? What are they like?
- Ethanol.
- Hydrogen chloride
- Phosgene.
- Chlorine.
There are two main methods for purifying chloroform from these impurities:
- plentiful washing with water followed by drying (allows you to completely get rid of ethanol);
- trichloromethane is washed with strong acid, then with a strong alkali, followed by water. Subsequent processing consists in drying using a water-taking agent - calcium chloride. Then the substance is distilled on a fractional column.
Discovery story
Since when is chloroform known? What is it and why was it used before? Let's try to figure it out.
The first mention of this substance dates back to 1831. It was then that the chemist Guthrie from Harbor obtained trichloromethane. However, his goal was not at all this substance, it was a successful by-product. The chemist was looking for solvents for rubber, experimented and accidentally received chloroform.
In the same year and a year later, two more scientists independently from each other receive this substance as a result of experiments. These are Eustace Liebig (who made a huge contribution to the development of chemistry) and Eugen Suberein. Their task was to find an anesthetic, and they found it. True, they learned about this effect of chloroform and began to use it a little later, only from the 1840s.
The structural formula and the interaction of atoms inside the molecule was able to study and build a chemical scientist Dumas in 1834. He proposed and assigned to chloroform its name, which he gave in honor of ants. In Latin, the ant is pronounced as formiata, and the formic acid contained in these insects can form from chloroform. Based on this, its name was determined.
Biological effect on humans
It fully justifies its use as an anesthetic chloroform. The effect on humans is very specific, it covers several major organ systems.
The degree of exposure depends on factors such as:
- concentration of respirable substance;
- duration of use;
- penetration method.
If we are talking about pure, medical chloroform, then its use is strictly dosed, precisely and topically. Therefore, of the possible contraindications, only a few are realized. If we are talking about evaporated chloroform in the composition of air and inhalation by man, then the action is already much more serious and destructive.
So, if you inhale trichloromethane for 10 minutes, there may be swelling of the airways, lung cramps, cough, sore throat. If the effect is not stopped, poisoning will occur immediately. The nervous system (both the brain and the spinal cord) will be affected, a lethal outcome is possible.
Chloroform also has a detrimental effect on the liver, digestive organs and kidneys. Its action is especially destructive if you take the solution inside. The following body reactions to taking chloroform are observed:
- dizziness;
- vomiting and nausea;
- persistent headaches;
- depression of the nervous system and, as a result, fatigue;
- fever;
- allergic rashes, redness of the skin.
Studies and experiments on different animals showed the following results:
- Prolonged ingestion of chloroform in the form of a liquid causes abortion, multiple pathologies and mutagenesis of future generations.
- When living in an atmosphere of chloroform, the animals were inhibited, sluggish and their lifespan was significantly reduced.
- Based on experiments on mice, it was concluded that trichloromethane is carcinogenic.
Such results were obtained by chemical scientists and doctors in studying the effects of chloroform on living organisms.
Medical use
The first mention of the use of this substance for medical purposes is rooted in 1847. It was then that the scientist, doctor, chemist Holmes Coot was the first to use chloroform as an anesthetic. This had a positive effect on the person during the operation period - a complete loss of consciousness, the absence of any sensations.
However, later, when the patient regained consciousness, it turned out that he did not stop nausea, vomiting. Then, more precise norms for the use of this substance were already established to avoid such consequences.
The English obstetrician James Simpson played a very large role in the introduction of chloroform into medicine. It was he who proved the positive value and action of the compound during the birth process.
However, over time, newer, safer, and more modern methods of anesthesia have appeared than chloroform. Its use in medicine has practically come to naught. Today it is used in the form of:
- component ointment for external use;
- as an additional anesthetic in combination with other substances and only in very small concentrations;
- as drops that relieve nausea and vomiting.
Industrial application
Chloroform is also used in industry. Its use refers to various chemical syntheses, where it is assigned the role of a solvent, degreaser, and the main or additional component to obtain important substances used in all areas of human activity.