Seaborgium hexacarbonyl, the most complex chemical compound with transactinoid, has been synthesized. Chemical names and formulas of substances How complex chemicals are formed

Most people do not think about the composition of the objects, substances, and matter around them. Atoms, molecules, electrons, protons - these concepts seem not only incomprehensible, but also far from reality. However, this opinion is wrong. Almost everything that surrounds us consists of chemical bonds. Chemical compounds are quite complex forms of substances. There are a great many such connections in the world around us. However, compounds consisting of only one chemical element can also belong to them, for example, oxygen or chlorine. Therefore, it is worth taking a closer look at the question: “What are chemical compounds?”

Complex "chemical" world

Few people think that the world around us consists of complex structures, macromolecules and tiny particles. It's amazing how different even the sizes of atoms are among different elements. The differences in atomic masses are also impressive - beryllium with its 9 a. e.m. is a “lightweight” compared to the “heavyweight” astatine: its atomic weight is 210 a. e.m. (a.e.m. - atomic mass units - a unit of measurement for the mass of atoms, molecules, nuclei, which is equal to 1/12 of the mass of a carbon atom in the ground state).

The diversity of elements also determines the presence of many chemical compounds (this, in simple words, is a combination of atoms of different and, in some cases, identical parts connected to each other). Most objects and substances are just this kind of compound. Oxygen necessary for life, table salt, acetone... One could go on for a very long time listing examples both known to everyone and understandable only to narrow specialists. What are these chemical compounds?

Definition, difference from mixtures

Chemical compounds are those that consist of atoms of different chemical elements connected to each other, however, there are exceptions: chemical compounds also include simple substances (that is, they consist of atoms of one element), if the atoms of these substances are connected by a covalent bond (it is formed by common to both atoms electrons). Such substances include nitrogen, oxygen, most halogens (in the periodic table, elements of the seventh group of the main subgroup; fluorine, chlorine, bromine, iodine, presumably astatine).

The concepts of “chemical compound” and “mixture of simple substances” are often confused. A mixture of substances is, as the name suggests, not an independent substance, but a system of two or more components. The very composition of these two units of chemicals is the main difference between them. As already mentioned, a combination of chemical elements and a mixture of simple (or complex) substances are not the same thing. Properties, methods of preparation, methods of separation into components are also distinctive criteria for mixtures and compounds. It is important to note that it is impossible to obtain or separate chemical compounds without chemical reactions, but mixtures can be done.

or elements?

Many people also confuse the phrases “compound of chemicals” and “compound of elements.” For unknown reasons, but most likely due to their incompetence, most of them do not see the difference between the first and second scientific concepts. It is worth learning and understanding that there is no such terminology as “chemical combination.” You should not repeat after others the mistakes of the etymology of certain not only expressions, but also words.

How to Define Connection Properties

Often the properties of chemical compounds are strikingly different from the properties of the elements from which they are composed. For example, the ethyl alcohol molecule consists of two carbon atoms, six hydrogen atoms and one oxygen atom, but its properties are strikingly different from the properties of all elements of its composition. Due to the fact that there are different classes of compounds, each of them has its own properties. Most reactions are, of course, characteristic of many compounds, but the mechanisms of their manifestation are different.

What classes are chemical compounds divided into?

Depending on their nature, there are classes of chemical compounds such as organic and inorganic. It is worth saying that substances (compounds) that contain carbon are called organic (with the exception of some compounds containing carbon, but classified as inorganic, they are listed below). The main groups of organic compounds are hydrocarbons, alcohols, aldehydes, ketones, esters, carboxylic acids, amides and amines. (compounds) do not contain carbon atoms in their composition, however, carbides, cyanides, carbonates and carbon oxides can be distinguished among them, since they, along with organic compounds, contain carbon atoms in their composition. Both compounds have their own characteristics, their own properties, and different groups of compounds of the same class may have different characteristics.

Inorganic compounds: basic properties

All inorganic compounds can be divided into several groups. Each of the data has common properties that often do not coincide with other groups of the same class. So, the answer to the questions of which chemical compounds are inorganic, which groups they form and what properties they have, can be presented as follows:

Complex inorganic compounds, their properties

As mentioned earlier, the second group of inorganic compounds can be divided into four subgroups:

• Oxides. This subgroup of inorganic compounds is characterized by reactions with water, acids and acid oxides (they have a corresponding oxygen-containing acid).
• Acids. These compounds react with water, alkalis and basic oxides (they have a corresponding base).
• Amphoteric compounds are compounds that can behave as both acids and bases (have both properties). Such compounds react with both acidic oxides and bases.
• Hydroxides. These substances dissolve indefinitely in water and change color when exposed to alkalis.

Organic compounds

Most of the objects that people come into contact with every day are made from organic compounds. Organic chemical compounds represent a wide class of bonds, compositions and properties of groups, in the interaction of which they are distinguished by enviable diversity. It is worth taking a closer look at the groups of these compounds.

Groups of organic compounds and some of their properties

1. Hydrocarbons. They are compounds of only hydrogen and carbon atoms. One can distinguish saturated and unsaturated, linear (acyclic) and carbocyclic, aromatic and non-aromatic; alkanes, alkenes, alkynes, dienes, naphthenes. All of these hydrocarbons have a common property that they are immiscible with water. Substitution reactions are typical for saturated ones, and addition reactions are typical for unsaturated ones.
2. Alcohols are compounds containing a hydroxyl (-OH) group (of course, organic compounds). They have the properties of weak acids, they are characterized by nucleophilic substitution reactions and oxidation reactions, and alcohols themselves can act as a nucleophile.
3. Ethers and esters. Ethers are slightly soluble in water and have weakly basic properties. Esters act as carriers of electrophilic reagents and undergo substitution reactions.
4. Aldehydes (contain an aldehyde -CHO group). They enter into reactions such as addition, oxidation, reduction, and conjugate addition.
5. Ketones. They are characterized by hydrogenation, condensation, and nucleophilic substitution.
6. Carboxylic acids. They exhibit, of course, acidic properties. Reduction, halogenation, nucleophilic substitution reactions at the acyl carbon atom, preparation of amides and nitriles, decarboxylation are the main characteristic reactions.
7. Amides. Hydrolysis, decomposition, acidity and basicity are the main characteristic reactions for amides.
8. Amines. Are the grounds; interact with water, acids, anhydrides, halogens and haloalkanes.

The classification of inorganic substances and their nomenclature are based on the simplest and most constant characteristic over time - chemical composition, which shows the atoms of the elements that form a given substance in their numerical ratio. If a substance is made up of atoms of one chemical element, i.e. is the form of existence of this element in free form, then it is called simple substance; if the substance is made up of atoms of two or more elements, then it is called complex substance. All simple substances (except monatomic ones) and all complex substances are usually called chemical compounds, since in them atoms of one or different elements are connected to each other by chemical bonds.

The nomenclature of inorganic substances consists of formulas and names. Chemical formula - depiction of the composition of a substance using symbols of chemical elements, numerical indices and some other signs. Chemical name - image of the composition of a substance using a word or group of words. The construction of chemical formulas and names is determined by the system nomenclature rules.

The symbols and names of chemical elements are given in the Periodic Table of Elements by D.I. Mendeleev. The elements are conventionally divided into metals And nonmetals . Non-metals include all elements of group VIIIA (noble gases) and group VIIA (halogens), elements of group VIA (except polonium), elements nitrogen, phosphorus, arsenic (VA group); carbon, silicon (IVA group); boron (IIIA group), as well as hydrogen. The remaining elements are classified as metals.

When compiling the names of substances, Russian names of elements are usually used, for example, dioxygen, xenon difluoride, potassium selenate. Traditionally, for some elements, the roots of their Latin names are introduced into derivative terms:

For example: carbonate, manganate, oxide, sulfide, silicate.

Titles simple substances consist of one word - the name of a chemical element with a numerical prefix, for example:

The following are used numerical prefixes:

An indefinite number is indicated by a numeric prefix n- poly.

For some simple substances they also use special names such as O 3 - ozone, P 4 - white phosphorus.

Chemical formulas complex substances made up of the notation electropositive(conditional and real cations) and electronegative(conditional and real anions) components, for example, CuSO 4 (here Cu 2+ is a real cation, SO 4 2 - is a real anion) and PCl 3 (here P +III is a conditional cation, Cl -I is a conditional anion).

Titles complex substances composed according to chemical formulas from right to left. They are made up of two words - the names of electronegative components (in the nominative case) and electropositive components (in the genitive case), for example:

CuSO 4 - copper(II) sulfate
PCl 3 - phosphorus trichloride
LaCl 3 - lanthanum(III) chloride
CO - carbon monoxide

The number of electropositive and electronegative components in the names is indicated by the numerical prefixes given above (universal method), or by oxidation states (if they can be determined by the formula) using Roman numerals in parentheses (the plus sign is omitted). In some cases, the charge of ions is given (for cations and anions of complex composition), using Arabic numerals with the corresponding sign.

The following special names are used for common multielement cations and anions:

For a small number of well-known substances it is also used special titles:

1. Acidic and basic hydroxides. Salts

Hydroxides are a type of complex substances that contain atoms of some element E (except fluorine and oxygen) and hydroxyl groups OH; general formula of hydroxides E(OH) n, Where n= 1÷6. Form of hydroxides E(OH) n called ortho-shape; at n> 2 hydroxide can also be found in meta-form, which includes, in addition to E atoms and OH groups, oxygen atoms O, for example E(OH) 3 and EO(OH), E(OH) 4 and E(OH) 6 and EO 2 (OH) 2.

Hydroxides are divided into two groups with opposite chemical properties: acidic and basic hydroxides.

Acidic hydroxides contain hydrogen atoms, which can be replaced by metal atoms subject to the rule of stoichiometric valency. Most acid hydroxides are found in meta-form, and hydrogen atoms in the formulas of acidic hydroxides are given first place, for example, H 2 SO 4, HNO 3 and H 2 CO 3, and not SO 2 (OH) 2, NO 2 (OH) and CO (OH) 2. The general formula of acid hydroxides is H X EO at, where the electronegative component EO y x - called an acid residue. If not all hydrogen atoms are replaced by a metal, then they remain as part of the acid residue.

The names of common acid hydroxides consist of two words: the proper name with the ending “aya” and the group word “acid”. Here are the formulas and proper names of common acid hydroxides and their acidic residues (a dash means that the hydroxide is not known in free form or in an acidic aqueous solution):

Less common acid hydroxides are named according to nomenclature rules for complex compounds, for example:

The names of acid residues are used to construct the names of salts.

Basic hydroxides contain hydroxide ions, which can be replaced by acidic residues subject to the rule of stoichiometric valence. All basic hydroxides are found in ortho-shape; their general formula is M(OH) n, Where n= 1.2 (less often 3.4) and M n+ is a metal cation. Examples of formulas and names of basic hydroxides:

The most important chemical property of basic and acidic hydroxides is their interaction with each other to form salts ( salt formation reaction), For example:

Ca(OH) 2 + H 2 SO 4 = CaSO 4 + 2H 2 O

Ca(OH) 2 + 2H 2 SO 4 = Ca(HSO 4) 2 + 2H 2 O

2Ca(OH)2 + H2SO4 = Ca2SO4(OH)2 + 2H2O

Salts are a type of complex substances that contain M cations n+ and acidic residues*.

Salts with general formula M X(EO at)n called average salts, and salts with unsubstituted hydrogen atoms - sour salts. Sometimes salts also contain hydroxide and/or oxide ions; such salts are called main salts. Here are examples and names of salts:

Acid and basic salts can be converted to middle salts by reaction with the appropriate basic and acidic hydroxide, for example:

Ca(HSO 4) 2 + Ca(OH) = CaSO 4 + 2H 2 O

Ca 2 SO 4 (OH) 2 + H 2 SO 4 = Ca 2 SO 4 + 2H 2 O

There are also salts containing two different cations: they are often called double salts, For example:

2. Acidic and basic oxides

Oxides E X ABOUT at- products of complete dehydration of hydroxides:

Acid hydroxides (H 2 SO 4, H 2 CO 3) acid oxides answer(SO 3, CO 2), and basic hydroxides (NaOH, Ca(OH) 2) - basicoxides(Na 2 O, CaO), and the oxidation state of element E does not change when moving from hydroxide to oxide. Example of formulas and names of oxides:

Acidic and basic oxides retain the salt-forming properties of the corresponding hydroxides when interacting with hydroxides of opposite properties or with each other:

N 2 O 5 + 2NaOH = 2NaNO 3 + H 2 O

3CaO + 2H 3 PO 4 = Ca 3 (PO 4) 2 + 3H 2 O

La 2 O 3 + 3SO 3 = La 2 (SO 4) 3

3. Amphoteric oxides and hydroxides

Amphotericity hydroxides and oxides - a chemical property consisting in the formation of two rows of salts by them, for example, for aluminum hydroxide and aluminum oxide:

(a) 2Al(OH) 3 + 3SO 3 = Al 2 (SO 4) 3 + 3H 2 O

Al 2 O 3 + 3H 2 SO 4 = Al 2 (SO 4) 3 + 3H 2 O

(b) 2Al(OH) 3 + Na 2 O = 2NaAlO 2 + 3H 2 O

Al 2 O 3 + 2NaOH = 2NaAlO 2 + H 2 O

Thus, aluminum hydroxide and oxide in reactions (a) exhibit the properties main hydroxides and oxides, i.e. react with acidic hydroxides and oxide, forming the corresponding salt - aluminum sulfate Al 2 (SO 4) 3, while in reactions (b) they also exhibit the properties acidic hydroxides and oxides, i.e. react with basic hydroxide and oxide, forming a salt - sodium dioxoaluminate (III) NaAlO 2. In the first case, the element aluminum exhibits the property of a metal and is part of the electropositive component (Al 3+), in the second - the property of a non-metal and is part of the electronegative component of the salt formula (AlO 2 -).

If these reactions occur in an aqueous solution, then the composition of the resulting salts changes, but the presence of aluminum in the cation and anion remains:

2Al(OH) 3 + 3H 2 SO 4 = 2 (SO 4) 3

Al(OH) 3 + NaOH = Na

Here, complex ions 3+ - hexaaqualuminium(III) cation, - - tetrahydroxoaluminate(III) ion are highlighted in square brackets.

Elements that exhibit metallic and non-metallic properties in compounds are called amphoteric, these include elements of the A-groups of the Periodic Table - Be, Al, Ga, Ge, Sn, Pb, Sb, Bi, Po, etc., as well as most elements of the B- groups - Cr, Mn, Fe, Zn, Cd, Au, etc. Amphoteric oxides are called the same as basic ones, for example:

Amphoteric hydroxides (if the oxidation state of the element exceeds + II) can be found in ortho- or (and) meta- form. Here are examples of amphoteric hydroxides:

Amphoteric oxides do not always correspond to amphoteric hydroxides, since when trying to obtain the latter, hydrated oxides are formed, for example:

If an amphoteric element in a compound has several oxidation states, then the amphotericity of the corresponding oxides and hydroxides (and, consequently, the amphotericity of the element itself) will be expressed differently. For low oxidation states, hydroxides and oxides have a predominance of basic properties, and the element itself has metallic properties, so it is almost always included in the composition of cations. For high oxidation states, on the contrary, hydroxides and oxides have a predominance of acidic properties, and the element itself has non-metallic properties, so it is almost always included in the composition of anions. Thus, manganese(II) oxide and hydroxide have dominant basic properties, and manganese itself is part of cations of the 2+ type, while manganese(VII) oxide and hydroxide have dominant acidic properties, and manganese itself is part of the MnO 4 - type anion. . Amphoteric hydroxides with a high predominance of acidic properties are assigned formulas and names modeled after acidic hydroxides, for example HMn VII O 4 - manganese acid.

Thus, the division of elements into metals and non-metals is conditional; Between the elements (Na, K, Ca, Ba, etc.) with purely metallic properties and the elements (F, O, N, Cl, S, C, etc.) with purely non-metallic properties, there is a large group of elements with amphoteric properties.

4. Binary compounds

A broad type of inorganic complex substances are binary compounds. These include, first of all, all two-element compounds (except for basic, acidic and amphoteric oxides), for example H 2 O, KBr, H 2 S, Cs 2 (S 2), N 2 O, NH 3, HN 3, CaC 2 , SiH 4 . The electropositive and electronegative components of the formulas of these compounds include individual atoms or bonded groups of atoms of the same element.

Multielement substances, in the formulas of which one of the components contains unrelated atoms of several elements, as well as single-element or multi-element groups of atoms (except hydroxides and salts), are considered as binary compounds, for example CSO, IO 2 F 3, SBrO 2 F, CrO (O2)2, PSI3, (CaTi)O3, (FeCu)S2, Hg(CN)2, (PF3)2O, VCl2 (NH2). Thus, CSO can be represented as a CS 2 compound in which one sulfur atom is replaced by an oxygen atom.

The names of binary compounds are constructed according to the usual nomenclature rules, for example:

For some binary compounds, special names are used, a list of which was given earlier.

The chemical properties of binary compounds are quite diverse, so they are often divided into groups by the name of anions, i.e. halides, chalcogenides, nitrides, carbides, hydrides, etc. are considered separately. Among binary compounds there are also those that have some characteristics of other types of inorganic substances. Thus, the compounds CO, NO, NO 2, and (Fe II Fe 2 III) O 4, the names of which are constructed using the word oxide, cannot be classified as oxides (acidic, basic, amphoteric). Carbon monoxide CO, nitrogen monoxide NO and nitrogen dioxide NO 2 do not have corresponding acid hydroxides (although these oxides are formed by non-metals C and N), nor do they form salts whose anions would include atoms C II, N II and N IV. Double oxide (Fe II Fe 2 III) O 4 - diiron(III)-iron(II) oxide, although it contains atoms of the amphoteric element - iron in the electropositive component, but in two different oxidation states, as a result of which, when interacting with acid hydroxides, it forms not one, but two different salts.

Binary compounds such as AgF, KBr, Na 2 S, Ba(HS) 2, NaCN, NH 4 Cl, and Pb(N 3) 2 are built, like salts, from real cations and anions, which is why they are called salt-like binary compounds (or simply salts). They can be considered as products of the substitution of hydrogen atoms in the compounds HF, HCl, HBr, H 2 S, HCN and HN 3. The latter in an aqueous solution have an acidic function, and therefore their solutions are called acids, for example HF (aqua) - hydrofluoric acid, H 2 S (aqua) - hydrosulfide acid. However, they do not belong to the type of acid hydroxides, and their derivatives do not belong to the salts within the classification of inorganic substances.

All substances are divided into simple and complex.

Simple substances- These are substances that consist of atoms of one element.

In some simple substances, atoms of the same element combine with each other to form molecules. Such simple substances have molecular structure. These include: , . All these substances consist of diatomic molecules. (Note that the names of the simple substances are the same as the names of the elements!)

Other simple substances have atomic structure, i.e. they consist of atoms between which there are certain bonds. Examples of such simple substances are all (, etc.) and some (, etc.). Not only the names, but also the formulas of these simple substances coincide with the symbols of the elements.

There is also a group of simple substances called. These include: helium He, neon Ne, argon Ar, krypton Kr, xenon Xe, radon Rn. These simple substances are made up of atoms that are not bonded to each other.

Each element forms at least one simple substance. Some elements can form not one, but two or more simple substances. This phenomenon is called allotropy.

Allotropy is the phenomenon of the formation of several simple substances by one element.

Different simple substances that are formed by the same chemical element are called allotropic modifications.

Allotropic modifications may differ from each other in molecular composition. For example, the element oxygen forms two simple substances. One of them consists of diatomic molecules O 2 and has the same name as the element-. Another simple substance consists of triatomic molecules O 3 and has its own name - ozone.

Oxygen O 2 and ozone O 3 have different physical and chemical properties.

Allotropic modifications can be solids that have different crystal structures. An example is the allotropic modifications of carbon C - diamond and graphite.

The number of known simple substances (approximately 400) is significantly greater than the number of chemical elements, since many elements can form two or more allotropic modifications.

Complex substances- These are substances that consist of atoms of different elements.

Examples of complex substances: HCl, H 2 O, NaCl, CO 2, H 2 SO 4, etc.

Complex substances are often called chemical compounds. In chemical compounds, the properties of the simple substances from which these compounds are formed are not preserved. The properties of a complex substance differ from the properties of the simple substances from which it is formed.

For example, sodium chloride NaCl can be formed from simple substances - metallic sodium Na and gaseous chlorine Cl. The physical and chemical properties of NaCl differ from the properties of Na and Cl 2.

In nature, as a rule, there are not pure substances, but mixtures of substances. In practical activities, we also usually use mixtures of substances. Any mixture consists of two or more substances called mixture components.

For example, air is a mixture of several gaseous substances: oxygen O 2 (21% by volume), (78%), etc. Mixtures are solutions of many substances, alloys of some metals, etc.

Mixtures of substances are homogeneous (homogeneous) and heterogeneous (heterogeneous).

Homogeneous mixtures- these are mixtures in which there is no interface between the components.

Mixtures of gases (in particular, air) and liquid solutions (for example, a solution of sugar in water) are homogeneous.

Heterogeneous mixtures- These are mixtures in which the components are separated by an interface.

Heterogeneous include mixtures of solids (sand + chalk powder), mixtures of liquids insoluble in each other (water + oil), mixtures of liquids and solids insoluble in it (water + chalk).

The most important differences between mixtures and chemical compounds:

1. In mixtures, the properties of individual substances (components) are preserved.
2. The composition of mixtures is not constant.

Most chemical reactions occurring in the world around us and used in industry are complex. Depending on the mechanism, they are divided into reversible,parallel,sequential,conjugate,chain.

Reversible reactions include reactions that, under given conditions, can spontaneously occur in both the forward and reverse directions. In general, the chemical equation of a reversible reaction is written as follows:

aA + bB+ … ↔cC+dD+ …,

where a,b, With,d,…. – stoichiometric coefficients in front of the initial (A, B, ....) and final formulas (C,D, ...) substances.

An example of a reversible process occurring in living organisms is the esterification reaction:

R 1 – COOH + HO – R 2 ↔ R 1 – C(O)O – R 2 + H 2 O,

and used in industry - the synthesis of ammonia from nitrogen and hydrogen:

3 H 2 +N 2 ↔ 2NH 3

Cthe rate of a reversible reaction is equal to the difference between the rates of the forward and reverse reactions.

Parallel reactions are reactions of the form:

i.e., in which the same starting substances, simultaneously reacting with each other, form different products.

An example of this type of reaction is the decomposition reaction of Berthollet salt KClO 3, which can proceed under certain conditions in two directions

In parallel, the decay of the atomic nuclei of some radioactive elements can occur through two or more mechanisms. Parallel reactions occur especially often in organic chemistry. For example, when toluene is sulfonated with sulfuric acid, ortho- and parasulfo derivatives can simultaneously form:

In some cases, biochemical reactions occurring in the cells of living organisms may also be parallel. For example, enzymatic fermentation of glucose:

1) C 6 H 12 O 6
2 C 2 H 5 OH+ 2CO 2

alcoholic fermentation

2) C 6 H 12 O 6
СH 3 – CH(OH) – COOH

lactic acid fermentation

Under certain conditions, many parallel reactions can proceed predominantly in only one direction.

The speed of a parallel reaction is determined by the speed of its fastest stage.

Sequential reactions are those in which the formation of the final product from the starting substances does not occur directly, but necessarily through a series of intermediate stages, occurring one after another in a strictly defined sequence. Schematically, this process can be depicted as follows:

A → B → C → D,

where each letter denotes a separate stage of the process. In general, the number of such stages in successive reactions can be very different (from several units to several tens). Moreover, each of the stages, in turn, is not necessarily a simple mono- or bimolecular reaction, but can also be complex.

Sequential reactions are common in nature and are especially often observed in biochemical processes occurring in living organisms and plants. Examples of such reactions include photosynthesis and biological oxidation of glucose, hydrolysis of oligo- and polysaccharides, etc.

Calculation of the kinetics of sequential reactions is complex and can be carried out quite accurately only for relatively simple processes consisting of a small number of stages.

However, if one of the stages of a sequential reaction has a significantly lower speed than all the others, then the overall reaction rate will be determined by the speed of this particular stage, which in this case is calledlimiting.

For example, the chlorination reaction of nitric oxide (II)

2NO+Cl 2 = 2NOCl

consists of two stages:

1) NO + Cl 2 = NOCl 2;

2) NOCl 2 + NO = 2NOCl

The first stage proceeds quickly with the formation of the unstable product NOCl 2. The second stage is slow and limiting. The rate of the entire reaction is described by the kinetic equation

= k
·CNO

and the overall order of this reaction is 2.

Reactions that proceed according to the following scheme are called conjugate:

One of these reactions can proceed independently, and the second reaction is feasible only in the presence of the first. Thus, the occurrence of one reaction initiates the implementation of the second.

Conjugate reactions are possible in biochemistry. They occur in cells, and the energy required for the second reaction with ΔG 2 > 0 is supplied by the first reaction, for which ΔG 1< 0. Причём │ΔG 1 │>│ΔG 2 │, i.e. the whole process as a whole proceeds with a decrease in the Gibbs energy. Such biochemical reactions are otherwise called tandem.

Often the mechanism of conjugate reactions consists in the formation in the first stage of active intermediate particles (radicals or ions), which initiate the occurrence of all other reactions.

The scheme of conjugate reactions of this type can be generally represented as follows:

where C is the active intermediate particle.

For example, benzene in an aqueous solution is not oxidized by H 2 O 2, but when divalent iron salt is added, it is converted into phenol and biphenyl. To “start this process, Fe 2+ ions first interact with H 2 O 2, forming radicals OH

Fe 2+ + H 2 O 2 → Fe 3+ + OH – + ˙ OH,

which then react as with benzene

C 6 H 6 + ˙ OH → ˙ C 6 H 5 + H 2 O

˙ C 6 H 5 + ˙ OH → C 6 H 5 OH

same with Fe 2+

Fe 2+ + ˙ OH→Fe 3+ +OH –

The phenomenon of chemical induction was first studied by N.A. Shilov in 1905

Chain reactions are chemical reactions that proceed through a series of regularly repeating elementary stages with the participation of active particles containing atoms with unpaired electrons at the external energy level (or, in other words, free radicals).

Chain reactions include combustion, polymerization and polycondensation, nuclear decay, etc.

The mechanism of chain reactions is that free radicals (often single atoms) have high chemical activity. They easily interact with stable molecules and transform them into active particles, which then form reaction products and new radicals, and thus a chain of further stages arises. The chain reaction continues until the entire substance reacts, or until the active radical particles disappear.

Chain reactions are characterized by three stages: 1) chain initiation; 2)chain development or growth; 3)open circuit.

The initiation of a chain begins with an elementary chemical act, as a result of which an active particle is formed. This process requires energy and can occur by heating the substance, exposure to ionizing radiation, or the action of a catalyst.

For example, in the reaction of the synthesis of hydrogen chloride and hydrogen and chlorine, which occurs according to a chain mechanism (H 2 + Cl 2 = 2HCl), the formation of a chain corresponds to the process

Cl2 2 ∙ Cl

Chain development is a periodic repetition of reaction steps involving the resulting radicals. They are otherwise called chain links:

H 2 + · Cl→HCl+ ˙ H

˙ H+Cl 2 →HCl+ ˙ Cl

H2+ ˙ Cl→HCl+ ˙ H

Cl2+ ˙ H→HCl+ ˙ Cli etc.

The length of the chain is determined by the number of molecules of the starting substance that reacted as a result of one act of chain nucleation before it breaks.

According to the characteristics of the stage of development, chain reactions are divided into unbranched And branched. In the first case, the number of free active radical particles remains unchanged throughout this entire stage.

In branched chain reactions the consumption of one active particle leads to the formation of several (two or more) other active particles. Schematically, this can be represented as follows:

Chain termination corresponds to the disappearance of active particles as a result of their interaction with each other:

˙ H+ ˙ H=H2

˙ Cl+ ˙ Cl=Cl 2 open circuit

˙ H+ ˙ Cl=HCl

In addition, it can occur during the adsorption of particles by the walls of a vessel, when two active particles collide with a third (called an inhibitor), to which the active particles give off excess energy. Therefore, chain reactions are characterized by the dependence of their speed on the size, shape and material of the reaction vessel, and on the presence of foreign inert substances that act as an inhibitor.

The speed of unbranched chain reactions is determined by the speed of the slowest stage, i.e. the origin of the chain. For each stage in reactions of this type, the usual equations of chemical kinetics (first or second order) are used.

Branched chemical reactions can proceed according to a complex kinetic law and have no specific order. The “reproduction” of radicals in them often leads to an avalanche-like process, which causes an explosion. However, chain termination is also possible in these reactions. Therefore, a rapid increase in the speed of the process (up to an explosion) occurs if the rate of branching of the chain exceeds the rate of its break. The theory of chain reactions was developed in the works of Academician N.N. Semyonova, S.N. Hinshelwood (England) and other scientists.

There are chain reactions in which the active particles are not radicals, but ions formed as a result of heterolytic cleavage of a chemical bond:

A : B → A ˉ : +B+

A similar mechanism in practice is often realized in polymerization reactions of unsaturated organic compounds.

An international team of scientists synthesized and studied seaborgium hexacarbonyl, Sg(CO)6, a compound of the unstable element with atomic number 106 with carbon monoxide, and also compared it with similar compounds of the unstable isotopes of molybdenum and tungsten, homologues of seaborgium. This is the most complex experimentally obtained chemical compound, which includes a transactinoid, that is, an element with an atomic number above 103. In the chemical properties of transactinoids, the effects of the theory of relativity for internal electrons are most pronounced, therefore the study of the chemistry of transactinoids makes it possible to clarify the entire theory of calculating the electronic structure of heavy atoms .

The periodic table of chemical elements is already filled up to number 118 (Fig. 1). Its entire structure reflects the periodicity of the chemical properties of elements with increasing atomic number, which arises with the gradual filling of electronic shells. If two chemical elements differ in the number of fully filled inner electron shells, but have similar outer electrons - which are responsible for chemical bonding - then the two elements should have similar chemical properties. These series of elements are called homologues of each other and in the periodic table they are located in the same group, one above the other. For example, the transition metals that form group six - chromium, molybdenum, tungsten and the superheavy element number 106 seaborgium - are homologues of each other. While the chemical properties of the first three of them have been known for a long time, the chemistry of seaborgium is just beginning to be studied. However, based on the periodic table, their chemical properties can be expected to be similar.

When comparing the chemical properties of homologous elements, there is one important pitfall. In heavy atoms, the internal electrons move at near-light speeds, and because of this, the effects of the theory of relativity work to their fullest. They lead to additional compression of the s- and p-orbitals and, as a consequence, to some expansion of the outer electron clouds. A large nuclear charge also enhances the effects of electrons interacting with each other, such as spin-orbit splitting. All this affects the chemical bond of a heavy atom with certain neighbors. And modern theoretical chemistry should be able to correctly calculate all these effects.

The heavier the atom, the stronger the relativistic effects. It seems natural to use the heaviest known elements, the transactinoids, elements with atomic number above 103, to test theoretical calculations (Figure 1). However, several significant difficulties arise on the way to their experimental study.

Firstly, the atomic nuclei of transactinoid elements are very unstable; their typical lifetimes are minutes, seconds, or even fractions of a second. Therefore, there is no talk of any accumulation of a macroscopic amount of matter; we have to work with individual atoms immediately after their birth.

This would not be a big problem if not for the second difficulty: these atoms can only be obtained in piece quantities. Superheavy atoms are synthesized in nuclear reactions, in the process of merging two other fairly heavy atoms with a large content of neutrons. To do this, a beam of heavy ions of one type is directed at a target containing heavy atoms of another type, and when they collide, nuclear reactions occur. In the overwhelming majority of cases, they generate only smaller fragments, and only occasionally does it happen that the desired superheavy nucleus is born in the merger of two nuclei. As a result, the rate of production of superheavy nuclei during continuous irradiation of a target turns out to be ridiculously low: on the order of one per minute, per hour, per day or even per week.

This birth technology leads to a third problem. The synthesis of superheavy atoms occurs under conditions of constant harsh radiation from a beam hitting the target, and, as a consequence, in the presence of a huge flow of extraneous nuclear debris. Even if the desired nucleus is born, takes on electrons from the environment, becomes a real atom and, finally, immediately behind the target enters into a chemical reaction with the formation of a new compound - this compound will be in harsh radiation conditions, in constant contact with plasma caused by hard ionization The fact that under these conditions it is generally possible to study some kind of chemistry of transactinoids up to flerovium (element 114) is in itself a great achievement. However, until now all chemical compounds involving transactinoids have been very simple from a chemical point of view - halides, oxides, and other similar compounds with a heavy atom in the maximum oxidation state. More fragile chemical compounds with non-trivial chemical bonds are quickly destroyed in the presence of harsh radiation. And all this, alas, makes it difficult to test the chemical properties of transactinoids.

The other day in a magazine Science was published, marking the beginning of "non-trivial" transactinoid chemistry. It reports the synthesis and experimental study of the compound Sg(CO) 6, seaborgium hexacarbonyl (Fig. 2). Moreover, in the same setup and with the same methods, hexacarbonyl complexes of the homologous elements seaborgium, Mo(CO) 6 and W(CO) 6 were also studied, and short-lived isotopes of molybdenum and tungsten with a half-life of several seconds or minutes.

The main highlight of this work is a combined experimental setup that brings together several technical advances of the last decade. This installation overcomes the third of the problems mentioned above - it spatially separates the area of ​​synthesis of superheavy nuclei and the area of ​​physicochemical research of the resulting compound. Its general appearance is shown in Fig. 3. At the entrance to the installation (from right to left in the background of the figure), a beam of nuclei interacts with the target and generates a “cocktail” of secondary nuclei. The reaction products are deflected by a dipole magnetic field (element D in the figure), and in different ways for different ratios of charge and mass of nuclei. The magnitude of the magnetic field is calculated in such a way that only the nuclei under study pass through the system of magnetic lenses (Q), while the background nuclei and the original beam are deflected away. In essence, this technique replicates the well-known mass spectrometry applied to nuclei.

In the next step, the separated nuclei (Sg, Mo or W) enter the RTC chamber, through which a gas mixture of helium and carbon monoxide is blown. An important point: on the way into the chamber, the nuclei pass through a window of strictly defined thickness, made of mylar. It dampens the kinetic energy of hot nuclei and allows them to thermalize (slow down to the energy of thermal motion of molecules) inside the gas chamber. There, the nuclei are “dressed with electrons” and, entering into a chemical reaction with carbon monoxide, form a compound - a carbonyl complex. Since the compound is volatile, it is transferred with the entire gas flow through a 10-meter Teflon capillary to the second part of the installation - a special COMPACT analyzer.

The name COMPACT stands for Cryo-Online Multidetector for Physics and Chemistry of Transactinoids. This installation is a whole line of 32 pairs of semiconductor detectors for gas thermochromatography of compounds of unstable elements. A strong temperature gradient is created along the line: each pair of detectors is at its own temperature, from +30°C at the beginning of the line to −120°C at its end. Each detector is capable of recording α and β particles emitted from nuclei during their decay, and measuring their energy and time of departure with high accuracy. This is necessary in order to identify seaborgium nuclei by their characteristic chain of decays, in which alpha particles of certain energies are emitted one after another, and not to confuse these rare events with background processes.

The COMPACT analyzer works like this. When the gas mixture is blown through the ruler, molecules of the carbonyl complex of the heavy metal are deposited on the surface of a particular detector, where they are recorded after radioactive decay. The number of the detector in which the decay is recorded indicates the temperature at which the absorption of the molecule becomes energetically favorable. This temperature is determined by the physicochemical characteristics of the carbonyl complex being studied - the enthalpy of adsorption. Well, this very characteristic of matter, in turn, is predicted by chemical calculations, in which relativistic effects play a significant role. Thus, by measuring how Sg(CO) 6 , W(CO) 6 and Mo(CO) 6 are deposited in the COMPACT analyzer, chemical theoretical calculations can be verified and the enthalpy of adsorption of these species can be measured.

The results of this study are shown in Fig. 4. Here are several characteristics in each of the 32 pairs of detectors. The top graph is simply the temperature distribution along a ruler. The middle and bottom graphs show, in fact, the experimental data themselves - the distribution of the recorded decays of tungsten-164 (in the center) and seaborgium-265 (bottom) nuclei across detectors. There are, of course, not enough events with seaborgium here - in two weeks of continuous irradiation of the target with an intense beam, a total of 18 of them were recorded. But nevertheless, it is clearly visible that they are not distributed evenly along the line, but closer to its end, in detectors with numbers above 20. Approximately the same picture was obtained when modeling this process with the enthalpy of adsorption, calculated quite recently in a theoretical work just for these substances. A similar picture is observed for compounds with an unstable tungsten isotope and with molybdenum isotopes (they are not shown in the figure): the maximum of the distributions falls exactly where theoretical calculations predict. This coincidence gives additional confidence that modern methods of fully relativistic calculation of the structure of heavy atoms adequately describe experimental data.

Finally, it is useful to take a bird's eye view of this research. Typically, unstable superheavy elements are of interest to physicists for the sake of new knowledge in nuclear physics. However, since nature allows us, these elements can be used for another purpose - to test how well we can predict chemical properties of such atoms. This knowledge, in turn, we need not in itself, but as an additional test of the entire modern theory of calculating the electronic structures of heavy atoms, taking into account relativistic effects. And from here numerous applications follow, from purely applied research to real fundamental science. The chemistry of transactinoids once again emphasizes how strongly the most diverse areas of physics and related disciplines are interconnected.