Nomenclature of chemical compounds: set of names, types and classification

The study of such an interesting subject as chemistry should begin with the basics of the basics, namely with the classification and nomenclature of chemical compounds. This will help not to get lost in such a complex science and put all the new knowledge in its place.

Briefly about the main thing

The nomenclature of chemical compounds is a system that includes all the names of chemicals, their groups, classes and rules, with the help of which the word formation of their names occurs. When was it developed?

The first nomenclature is chemical. compounds was developed in 1787 by the Commission of French chemists under the leadership of A. L. Lavoisier. Until that time, the names were given to substances arbitrarily: by some signs, by the methods of preparation, by the name of the discoverer, and so on. Each substance could have several names, that is, synonyms. The Commission decided that any substance should have only one single name; the name of a compound substance can consist of two words indicating the type and genus of the compound, and should not contradict linguistic standards. This nomenclature of chemical compounds became a model for the creation at the beginning of the 19th century of nomenclatures of various nationalities, including Russian. This will be discussed further.

Types of nomenclature of chemical compounds

It seems that understanding chemistry is simply impossible. But if you familiarize yourself with the two types of chemical nomenclature. connections, you can make sure that everything is not so complicated. What is this classification? Here are two types of chemical nomenclature:

• inorganic;
• organic.

What are they like?

Simple substances

The chemical nomenclature of inorganic compounds is the formulas and names of substances. A chemical formula is an image of symbols and letters that reflects the composition of a substance using the Periodic System of Dmitry Ivanovich Mendeleev. A name is an image of the composition of a substance using a specific word or group of words. The construction of formulas is carried out according to the rules of the nomenclature of chemical compounds, and, using them, a designation is given.

The name of some elements is derived from the root of these names in Latin. For instance:

• C - Carbon, lat. carboneum, carb root. Examples of compounds: CaC — calcium carbide; CaCO ₃ - calcium carbonate.
• N - Nitrogen, lat. nitrogenium, the root is nitr. Examples of compounds: NaNO ₃ - sodium nitrate; Ca ₃ N ₂ - calcium nitride.
• H - Hydrogen, lat. hydrogenium, hydro root. Examples of compounds: NaOH - sodium hydroxide; NaH is sodium hydride.
• O - Oxygen, lat. oxygenium, root "oks". Examples of compounds: CaO - calcium oxide; NaOH - sodium hydroxide.
• Fe - Iron, lat. ferrum, the root of "ferr." Examples of compounds: K ₂ FeO ₄ - potassium ferrate and so on.

In order to describe the number of atoms in a compound, prefixes are used. In the table for examples, substances of both organic and inorganic chemistry are taken.

Organic matter

Compounds of organic chemistry are not so simple as with inorganics. The fact is that the principles of the chemical nomenclature of organic compounds are based immediately on three types of nomenclatures. At first glance, this seems surprising and confusing. However, they are quite simple. Here are the types of chemical nomenclature:

• historical or trivial;
• systematic or international;
• rational.

Currently, it is they that are used to give a name to one or another organic compound. Let us consider each of them and make sure that the nomenclature of the main classes of chemical compounds is not so complicated as it seems.

Trivial

This is the very first nomenclature that appeared at the beginning of the development of organic chemistry, when there was neither a classification of substances, nor a theory of the structure of their compounds. Organic compounds were randomly assigned by source. For example, malic acid, oxalic acid. Also distinguishing criteria by which the names were given were color, smell and chemical properties. However, the latter was rarely an occasion, because during this period of time relatively little information was known about the possibilities of the organic world. However, many names of this rather old and narrow nomenclature are often used to this day. For example: acetic acid, urea, indigo (violet crystals), toluene, alanine, butyric acid, and many others.

Rational

This nomenclature has arisen since the advent of the classification and the unified theory of the structure of organic compounds. It has a national character. Organic compounds get their names according to the type or class to which they belong, according to their chemical and physical characteristics (acetylenes, ketones, alcohols, ethylenes, aldehydes and so on). Currently, this nomenclature is used exclusively in cases where it gives a clear and more detailed picture of the compound in question. For example: methylacetylene, dimethylketone, methyl alcohol, methylamine, chloroacetic acid and the like. Thus, from the name it immediately becomes clear what the organic compound consists of, but a more precise arrangement of the substituent groups is still not possible to determine.

International

Its full name is the systematic international nomenclature of chemical compounds IUPAC (IUPAC, International Unionof Pureand Applied Chemistry, International Union of Theoretical and Applied Chemistry). It was developed and recommended by the IUPAC congresses in 1957 and 1965. The rules for international nomenclature published in 1979 were compiled in the Blue Book.

The foundation of a systematic nomenclature of chemical compounds is the modern theory of the structure and classification of organic substances. This system aims to solve the main problem of the nomenclature: the name of all organic compounds should include the correct names of the substituents (functions) and their support - the hydrocarbon skeleton. It must be such that it can be used to determine the only true structural formula.

The desire to create a unitary chemical nomenclature for organic compounds originated in the 80s of the XIX century. This happened after the creation of a theory of chemical structure by Alexander Mikhailovich Butlerov, in which there were four main provisions that talked about the order of atoms in a molecule, the phenomenon of isomerism, the relationship of the structure and properties of matter, as well as the effect of atoms on each other. This event took place in 1892 at the congress of chemical scientists in Geneva, which approved the rules for the nomenclature of organic compounds. These rules went into organics called the Geneva Nomenclature. Based on it, a popular Beilstein guide was created.

Naturally, over time, the amount of organic compounds increased. For this reason, the nomenclature was becoming more complicated all the time, and new additions arose and were voiced and adopted at the next congress held in 1930 in the city of Liege. Innovations were based on convenience and brevity. And now the systematic international nomenclature has incorporated some provisions of both Geneva and Liege.

Thus, these three types of systematization are the main principles of the chemical nomenclature of organic compounds.

Classification of simple compounds

Now it's time to get acquainted with the most interesting: the classification of both organic and inorganic substances.

Now the world knows thousands of different inorganic compounds. Knowing all their names, formulas and properties is almost impossible. Therefore, all substances of inorganic chemistry are divided into classes grouping all compounds according to a similar structure and properties. Such a classification is presented in the table below.

For the first separation, we used how many elements the substance consists of. If the atoms of one element, then it is simple, but if of two or more - complex.

Consider each class of simple substances:

1. Metals are elements located in the first, second, third groups (except boron) of the periodic table of D. I. Mendeleev, as well as elements of decades, lantonoids and octinoids. All metals have common physical (malleability, thermal and electrical conductivity, metallic luster) and chemical (reducing, interaction with water, acid and so on) properties.
2. Non-metals include all elements of the eighth, seventh, sixth (except polonium) groups, as well as arsenic, phosphorus, carbon (from the fifth group), silicon, carbon (from the fourth group) and boron (from the third).
3. Amphoteric compounds are those compounds that can exhibit the properties of both non-metals and metals. For example, aluminum, zinc, beryllium and so on.
4. Noble (inert) gases include elements of the eighth group: radon, xeon, krypton, argon, neon, helium. Their common property is low activity.

Since all simple substances consist of atoms of the same element of the Periodic System, their names usually coincide with the names of these chemical elements of the table.

In order to distinguish between the concepts of “chemical element” and “simple substance”, despite the similarity of the names, one must understand the following: with the help of the first a complex substance is formed, it binds to atoms of other elements, it cannot be considered separately from any complex substance. The second concept lets us know that this substance has its own properties, without binding to others. For example, there is oxygen that is part of the water, and there is oxygen that we breathe. In the first case, the element as part of the whole is water, and in the second - as the substance in itself, which the organism of living creatures breathes.

Now consider each class of complex substances:

1. Oxides is a complex substance consisting of two elements, one of which is oxygen. Oxides are: basic (when dissolved in water, they are formed in the base), amphoteric (formed using amphoteric metals), acidic (formed by non-metals in oxidation states from +4 to +7), double (formed with the participation of metals in different oxidative degrees ) and non-salt forming (for example, NO, CO, N ₂ O and others).
2. Hydroxides include substances that have in their composition a group - OH (hydroxyl group). They are: basic, amphoteric and acid.
3. Salts are called such complex compounds, which include a metal cation and anion of an acid residue. Salts are: medium (metal cation + anion of an acid residue); acidic (metal cation + unsubstituted hydrogen atom (s) + acid residue); basic (metal cation + acid residue + hydroxyl group); double (two metal cations + acid residue); mixed (metal cation + two acid residues).
4. A binary compound is a two-element compound or multi-element, comprising not more than one cation, or anion, or complex cation, or anion. For example, KF, CCl ₄ , NH ₃ and so on.
5. Acids include such complex substances whose cations are exclusively hydrogen ions. Their negative anions are called acid residues. These complex compounds can be oxygen-containing or oxygen-free, monobasic or dibasic (depending on the number of hydrogen atoms), strong or weak.

Classification of Organic Compounds

As you know, any classification is based on certain characteristics. The basis for the modern classification of organic compounds are two of the most important features:

• carbon skeleton structure;
• the presence of functional groups in the molecule.

A functional group is those atoms or a group of atoms on which the properties of substances depend. According to them, it is determined to which class this or that compound belongs.

• alcohols (-OH);
• aldehydes (-COH);
• carboxylic acids (-COOH);
• amines (-NH ₂ ).

For the concept of the first separation of hydrocarbons into cyclic and acyclic classes, it is necessary to get acquainted with the types of carbon chains:

• Linear (carbons are located along a straight line).
• Branched (one of the carbons of the chain has a bond with the other three carbons, that is, a branch is formed).
• Closed (carbon atoms form a ring, or cycle).

Those carbons that have cycles in their structure are called cyclic, and the rest are called acyclic.

Brief description of each class of organic compounds

1. Limit hydrocarbons (alkanes) are not capable of joining hydrogen and any other elements. Their general formula is C _n H _{2n + 2} . The simplest representative of alkanes is methane (CH ₄ ). All subsequent compounds of this class are similar to methane in their structure and properties, but differ in composition by one or more groups -CH ₂ -. Such a series of compounds obeying this pattern is called homologous. Alkanes are capable of entering into reactions of substitution, combustion, decomposition and isomerization (conversion to branched-chain carbons).
2. Cycloalkanes are similar to alkanes, but have a cyclic structure. Their formula is C _n H _2n . They can participate in reactions of addition (for example, hydrogen, while becoming alkanes), substitution and dehydrogenation (removal of hydrogen).
3. Unsaturated ethylene hydrocarbons (alkenes) include hydrocarbons with the general formula C _n H _2n . The simplest representative is ethylene - C ₂ H ₄ . They have in their structure one double bond. Substances of this class participate in the reactions of addition, combustion, oxidation, polymerization (the process of combining small identical molecules into larger ones).
4. Diene (alkadiene) hydrocarbons have the formula C _n H _2n-2 . They already have two double bonds and are capable of entering into the reactions of addition and polymerization.
5. Acetylene (alkynes) differ from other classes in the presence of one triple bond. Their general formula is C _n H _2n-2 . The simplest representative is acetylene - C ₂ H _2. Enter into the reaction of addition, oxidation and polymerization.
6. Aromatic hydrocarbons (arenas) are named so because some of them have a pleasant smell. They have a cyclic structure. Their general formula is C _n H _2n-6 . The simplest representative is benzene - C ₆ H ₆ . They can undergo halogenation reactions (replacement of hydrogen atoms by halogen atoms), nitration, addition and oxidation.