Handout material for lecture 5

Lecture 5

AROMATIC HYDROGENES

KEY WORDS: aromatic carbohydrates, arenes, sp2-hybridization, single p-electronic loss, circular generation, ion mechanism of substitution reaction, electrophilic substitution, nitrification, halogenation, alkylation Friedel-Crafts, alkylation of alkenes, hydr.

BUDOV BENZENE MOLECULES. AROMATICITY

Aromatic carbohydrates (arenes) – these are carbohydrate molecules, which contain just a few benzene rings.

The simplest representative of aromatic carbohydrates is benzene, the molecular formula of which is 6 H 6. It has been established that the atoms and carbons of the benzene molecule lie on the same plane, creating a regular hexagon (Fig. 1). The carbon atom is bound to one water atom. The maximum value of all carbon-coal viscosities, however, becomes 0.139 nm.

Formulas a) and b) were coined in 1865 by the German chemist August Kekule. Regardless of those who do not accurately convey the molecules of benzene, they are called Kekulé formulas.

Historically, the name “aromatic carbohydrates” was due to the fact that they are rich in benzene-like substances, which were first seen from natural sources, but have a slightly unpleasant odor.

Nina, under the concept of “aromaticity,” looms large in respect, above all, the special nature of the reactionary nature of speech, reasoning, its own color, the peculiarities of the natural molecules of these compounds.

What are these particularities?

It is similar to the molecular formula C 6 H 6 benzene and unsaturated compounds, and it turns out that addition reactions typical for alkenes would be typical for this type. Please note that in which alkenes readily enter into an addition reaction, benzene does not react and reacts completely. Benzene does not give the characteristic clear reactions that occur in non-saturated carbohydrates: wine does not disturb bromine water and water dissolution of potassium permanganate.

This nature of the reaction is explained by the presence in the aromatic ring of the resulting system - a single p-electronic darkness.

In the benzene molecule, the carbon atom is present at the site sp 2-hybridization and cross-breeding s-bonds with two carbon atoms and one atom of water. The fourth valence electron of a carbon atom is located on p-orbitals perpendicular to the surface of the molecule The benzene molecule is more likely to overlap R-orbitals of the skin atom of carbon R-orbitals of both surface atoms of carbon (Fig. 2) As a result of this One p-electronic chaos, spread over and under the surface of the benzene ring – affects mutual agreement.

Such a cyclic system with a burning gloom from six electrons is very stable and energetically visible; Therefore, it is important for benzene to enter into those reactions in which the aromatic ring is preserved.

A

b

Rice. 2. Electronic molecule of benzene: a) recurve diagram R-orbitals; b) one p-electron mess.

Let us emphasize once again that in a benzene molecule one cannot see three double bonds and three simple bonds. The electronic strength is distributed evenly in the molecule, and the bonds between the carbon atoms are absolutely the same. It should be remembered that the Kekule formula, which is often used to represent benzene, is mental and does not represent the real molecule.

Also, aromatic compounds are molecules in which there is a stable cyclic grouping with a special binding character. Having a molecular formula that indicates a high level of insaturation, these compounds, however, do not react as if they were insaturation, but rather enter into a substitution reaction due to the preservation of the aromatic system.

BENZENE HOMOLOGUES,

Isomerism, NOMENCLATURE

The formula is homologous to the series of aromatic carbohydrates CnH2n-2.

The closest homologue to benzene is methylbenzene. The most common name for this trivial name is toluene:

Benzene and toluene do not contain aromatic isomers. For these speeches it is characteristic that Interclass isomerism. Thus, they correspond to the molecular formula C 6 H 6 and, therefore, isomers of benzene are non-permeable non-cyclic carbohydrates, which contain two triplicate or two subdivonic and one triple bonds in the molecule, for example:

Beginning with arenes with very carbon atoms, the possibility of isomerism associated with storage and mutual distribution of carbohydrate radicals. Since two protectors are connected to the benzene ring, the stinks can be in three different positions or one of one: the hand (this position is indicated by the prefix ortho-), through one carbon atom ( meta-), and on the contrary one of one ( pair-). Dimethylbenzene, structural formulas of isomers which are lower, may have a trivial name xylol

Thus, the molecular formula C 8 H 8 shows that there are isomeric aromatic carbohydrates:

Aromatic carbohydrates become an important part of the cyclical series of organic compounds. The simplest representative of such carbohydrates is benzene. The formula of this word not only saw other carbohydrates, but also gave rise to the development of new directly organic chemistry.

Type of aromatic carbohydrates

Aromatic carbohydrates were added to the cob of the 19th century. At that time, the most widely used source for street lighting was lighting gas. From this condensate, the great English physicist Michael Faraday saw three grams of oily speech in 1825, describing this power and calling it: carburation water. In 1834, a German scientist, the chemist Mitscherlich, heated benzoic acid with vapor, removing benzene. The formula behind this reaction is presented below:

C6 H5 COOH + CaO alloy C6 H6 + CaCO3.

Sometimes benzoic acid is extracted from benzoic resin, which can be found in many tropical plants. In 1845, the new product was discovered in coal tar, which was a readily available raw material for extracting the new product on an industrial scale. Another source of benzene is naphtha, obtained from various families. In order to ensure the demand of industrial enterprises for benzene, it is eliminated by aromatization of certain groups of acyclic carbohydrate naphtha.

The current version was named based on the German teachings of Liebich. The root of the word “benzene” is joked in Arabic languages ​​– there it is translated as “incense”.

Physical power of benzene

Benzene is a barren-free liquid with a specific odor. This mixture boils at a temperature of 80.1 C, solids at 5.5 C and transforms into a white crystalline powder. Benzene practically does not conduct heat or electricity, it is bad in water and good in various oils. The aromatic power of benzene reflects the essence of the structure of its internal substance: the stable benzene core and the unimportant warehouse.

Chemical classification of benzene

Benzene and its homologues - toluene and ethylbenzene - are an aromatic series of cyclic carbohydrates. The skin contains the widest structure, called the benzene ring. The structure of the skin's viscosity is characterized by a special cyclic grouping made up of six carbon atoms. Vaughn won the name of the benzene aromatic nucleus.

Discovery history

The installation of internal benzene took nearly a decade. The basic principles of Budov (the ring model) were proposed in 1865 by the chemist A. Kekule. As the legend reveals, the German tradition has studied the formula of this element in the past. Later they introduced a simpler written structure of the word called benzene. The formula of this speech is a six-piece. Symbols of coal and water, which loom and grow in the tufts of the six-cut tree, are lowered. In this way, it turns out to be a simple regular six-piece with single and double lines on the sides that are drawn. The formula for benzene is presented below.

Aromatic carbohydrates and benzene

The chemical formula of this element allows for hardening, which is not typical for benzene. For this and other elements of the aromatic series, a typical reaction is the substitution of water atoms in the benzene ring.

Sulfurization reaction

To ensure the interaction between concentrated sulfuric acid and benzene, benzosulfonic acid and water can be removed by raising the reaction temperature. The structural formula of benzene for this reaction looks like this:

Halogenation reaction

Bromine or chromium in the presence of a catalyst interacts with benzene. In some cases, halogen derivatives appear. And the nitration reaction axis is generated from concentrated nitric acid. The final result of the reaction is the nitrogen reaction:

For additional nitration, remove the Vibuch's compound - TNT or trinitotoluene. Few people know that the body is based on benzene. Many other nitrogen compounds based on the benzene ring can also be vicorins and vibuchs.

Electronic formula for benzene

The standard formula of the benzene ring does not accurately represent the inner benzene. Therefore, benzene is responsible for its three localized bonds, which are responsible for the interaction with two carbon atoms. However, as evidence shows, benzene does not contain any special ligaments. The molecular formula of benzene allows the bonds in the benzene ring to be equal. The skin value of them is approximately 0.140 nm, which is intermediate values ​​between that of a standard binder (0.154 nm) and a flexible ethylene binder (0.134 nm). The structural formula of benzene, depicted from the drawing of bonds, is not complete. A more plausible model is the trivial model for benzene, which looks like the one shown in the picture below.

The skin with atoms of the benzene ring is found at the stage of sp 2 -hybridization. It spends three valence electrons on the formation of sigma bonds. These electrons consume two natural atoms in carbohydrates and one atom in water. In this case, the electrons and bonds C-C, H-H are in the same plane.

The fourth valence electron creates confusion in the shape of a volumetric tube, spread perpendicular to the surface of the benzene ring. This electronic shadow overlaps above the surface of the benzene ring and directly below it from the shadows of the two neighboring carbon atoms.

The thickness of the electrons in this speech is evenly distributed among all the carbon ligaments. This is the way to create one ring of electronic darkness. In modern chemistry, this structure was called an aromatic electron sextet.

The value of internal viscosities to benzene

The very same value of all facets of hexacutane is explained by the diversity of aromatic bonds, which correspond to the characteristic chemical and physical properties of benzene. The formula for the equal distribution of electronic powder and the equal value of all internal ligaments is shown below.

As you can see, instead of single and semi-winter rice, which is cut, the internal structure is formed in the form of a cola.

The essence of the internal structure of benzene provides the key to understanding the internal structure of cyclic carbohydrates and expands the possibilities of practical stagnation of these substances.

Aromatic and carbohydrate– because of carbon and water, the molecule has a benzene ring. The most important representatives of aromatic carbohydrates are benzene and its homologues - products of substitution of one or more water atoms in the benzene molecule with excess carbohydrates.

Budova benzene molecules

Persha is aromatic with spoluka – benzene – bula vidkrita at 1825 r. M. Faraday. Its molecular formula was established - 3 6 H 6. Once this warehouse is equalized from the warehouse of the boundary carbohydrate, which contains the same number of carbon atoms, - hexane (3 6 H 14), it can be noted that benzene belongs to the whole There are fewer atoms in water. Apparently, changes in the number of water atoms in a carbohydrate molecule result in the appearance of multiple bonds and cycles. In 1865 F. Kekule gave his structural formula as cyclohexanthriene - 1, 3, 5.

In this manner, a molecule that demonstrates Kekule's formula Because of the presence of subsurface bonds, benzene is due to its non-absorbing character, so it is easy to enter into addition reactions: hydration, bromination, hydration, etc.

However, data from numerical experiments have shown that benzene enters into the reaction of adding solids in harsh washings (at high temperatures and lightening), and is stable until oxidation. The most characteristic of this reaction is the substitution reaction, however, benzene is closer in character to carbohydrates.

In an effort to explain these inconsistencies, many different variations of the structure of benzene have been proposed. The remaining benzene molecule was confirmed by the reaction of its solution with acetylene. In fact, carbon - the carbon bonds in benzene are of equal value, and their strength is not similar to the strength of either single or double bonds.

Currently, benzene is designated either by the Kekule formula, or by the six-knot, in which it is represented by a colo.

So why does benzene have a special structure? On the basis of data from researchers and researchers, a summary has been compiled about the fact that all six carbon atoms are present in the plant sp 2 -hybridization and lie in the same plane. Non-hybridized p-orbitals of carbon atoms, which form sub-links (Kekule formula), perpendicular to the ring plane and parallel to one another.

The stench overlaps with each other, creating a single π-system. Thus, the system of subordinate ligaments that overlap, depicted in Kekule’s formula, is a cyclical system of connections that overlap with each other - ligaments. This system has two toroidal (donut-like) areas of electron density that lie on the opposite side of the benzene ring. Thus, it is more logical to depict benzene as a regular hexatriene with a stake at the center (π-system), while it is less logical to represent cyclohexatriene-1,3,5.

The American opinion of L. Pauling proposed to represent benzene in the form of two boundary structures, which are divided by the distribution of electron power and gradually transform one into one, in order to respect its adjacent connections, averaging the two structures .

Given to the world, dovzhin ties confirm tsi stewed. It is clear that all 3-3 bonds in benzene are of the same magnitude (0.139 nm). The stench is short for single N-W bonds (0.154 nm) and longer for sub-links (0.132 nm).

There are also molecules that form a number of cyclic structures.

Isomerism and nomenclature

Homologues of benzene are characterized by The isomerism of the position of many intercessors. The simplest homologue of benzene – toluene (methylbenzene) – does not have such isomers; the next homolog of representations in the form of four isomers:

The basis for the name of an aromatic carbohydrate with small mixtures is the word benzene. The atoms in the aromatic ring are numbered, starting from the oldest patron to the youngest:

Following the old nomenclature, positions 2 and 6 are called orthopositions, 4 - pair-, and 3 and 5 - meta-positions.

Physical power
Benzene and its simplest homologues are quite toxic in most people with a characteristic unpleasant odor. The bad stench comes out in the water, but the good stuff comes out in organic liquids.

Chemical power of benzene

Substitution reactions. Aromatic carbohydrates are included in the substitution reaction.
1. Bromuvannya. When reacting with bromine in the presence of a catalyst, bromide (ΙΙΙ), one of the water atoms in the benzene ring can be replaced by a bromine atom:

2. Nitration of benzene and its homologues. When an aromatic carbohydrate interacts with nitric acid in the presence of sulfuric acid (the combination of sulfuric acid and nitric acid is called a nitric acid), the water atom is replaced by a nitro group -NO 2:

Renewal of nitrobenzene, which, having settled in this reaction, removes aniline - a substance that is used to remove aniline barberries:

This reaction is due to the Russian chemist Zinin.
Acceptance reaction. Aromatic compounds may react with the benzene ring. In whom is cyclohexane resolved?
1. Hydraulic bath. Catalytic hydrogenation of benzene occurs at higher temperatures, lower hydrogenation of alkenes:

2. Chlorination. The reaction occurs when clarified with ultraviolet light and is completely radical:

Homologues of benzene

The composition of their molecules corresponds to the formula n H 2 n-6. The closest homologs to benzene:

In all cases, toluene homologues to benzene may be isomeric. Isomerism can be associated both with the number and position of the protector (1, 2), and with the position of the protector in the benzene ring (2, 3, 4). Connection of the halal formula Z 8 N 10:

Following the old nomenclature, which is used to indicate the distinct distribution of two or different protectors on the benzene ring, the prefixes are used ortho- (shortly pro-) - defenders of coal from the surrounding atoms, meta-(m-) – through one carbon atom pair— (P-) - The intercessors are one against one.
The first members of the homologous series to benzene have a specific odor. The stench lay behind the water. And garni raschinniks.

Homologues of benzene react substitution ( bromovannya, nitruvanya). Toluene is oxidized by permanganate when heated:

Homologs of benzene are used as agents for the extraction of barnacles, as well as for the protection of plants, plastics, and liquids.

Benzene is stronger than visions M. Faraday 1825 rock from the condensate that came from the lamp gas, which is used to lighten the streets of London. Faraday called this rare, easily crumbly liquid with a pungent odor “carburated hydrogen.” It is important to note that it was established that benzene consists of equal parts carbon and water.

Much later, in 1834, Mitscherlikh removing benzene and decarboxylating benzoic acid. Having established the elemental warehouse of the removed connection – З 6 Н 6 – and having established its name for the new one – petrol. However, Libikh did not like this name. It occurred to him that he should put benzene on a par with such distant words as quinine and strychnine. In Libikh’s opinion, the more distant name for the new half is benzene, the fragments show the closeness of benzene to the authorities up to the whole (such as the German ol- oil). There were other propositions. The fragments of benzene were seen by Faraday from the lighting gas, and Laurent was renamed (1837 rubles) for a new name pheno from the Greek “carry light.” This name has not been established, but it itself is similar to the name of the monovalent excess benzene - phenyl.

Faraday was not spared in carbohydrates. All the names assigned to him turned out to be defective. From the Libikhov name, “benzene” comes from the fact that it half-replaces the hydroxyl group, which is not there. So Mitscherlikhivsky “gasoline” itself does not contain the functional nitrogen group. Moreover, the emergence of different names caused a subset of chemists. In German and Russian scientific literature, the name “benzene” has been established, and in English and French – “benzene” ( bensene, toluene, xylene).

At first glance, it seems that installing natural benzene is not very difficult. The benzene molecule contains only two elements, and six atoms of carbon contain six atoms of water. Moreover, the physical and chemical influences on benzene have been very effective. However, this work dragged on for more than a decade and ended in just 1931.

The most important barriers to the discovery of the structure of benzene were prepared by the eminent German chemist Kekule. From the height of current knowledge, it is important to understand and evaluate the significance of the hypothesis proposed by him, behind which benzene molecule is cyclic (1865). However, this very assumption, when taken together with the number of isomers in mono- and disubstituted benzenes, led to the well-known Kekule formula. According to Kekul, benzene is a six-membered cyclic compound with three subligaments that are interconnected. cyclohexatriene

This structure itself is made possible by the presence of one or more monosubstituted benzenes and three isomers of disubstituted benzenes.

From the moment Kekule's structure appeared, criticism began, which, unfortunately, was entirely deserved. It was already understood that rice is characterized by aromatic flavors - its powerful aromatic character. Kekule's structure for benzene proved impossible to explain the peculiarity of aromatic compounds. In a number of cases, she could not explain the presence of isomers, even though the formula for cyclohexatriene for benzene allowed its use. So, ortho-substituted benzenes can be of two isomers

Prote reveal їх zirvala. It is very significant that from this point of view it is difficult for Kekule to consider benzene as a cyclohexatriene with loose, non-fixed, sub-ligaments. As a legacy of the Swedish re-creation I axis II And likewise, benzene behaves like a structure made up of equal parts Iі II.

However, the main problem with Kekule’s benzene is the inability to explain on its basis the aromatic character of the compound, which has a benzene ring in its molecule. Yakbi benzene is cyclohexatriene, then. connected with three subligaments, in mav bi:

It is easy to oxidize with cold water solution of KMnO 4,

Even at room temperature, bromine is added and easily enters into other electrophilic addition reactions,

The liquid is hydrated with water in the presence of nickel at room temperature,

In this reaction, benzene enters reluctantly, not like alkenes. And the substitution reaction axis is even more characteristic of the semi-aromatic series. The star shows that benzene cannot be cyclohexatriene and Kekule's formula does not represent true benzene. The main disadvantage of benzene Kekule is the presence of new sub-ligaments. If they were not there, then there is no trace of benzene showing power, associated alkenes. The connection with this becomes reasonable, which is why all further attempts to “refine” Kekule’s formula will help to eliminate the sublinks, while preserving the cyclic nature of benzene. These are the formulas III – VII, founded by Klaus (b. 1867), Dewar (b. 1867), Armstrong - Bayer (b. 1887), Thiele (b. 1899) and Ladenburg (b. 1869)

None of these formulas could explain all the powers that influence benzene. This has become possible only with the development of quantum chemistry.

It is evident to the recent discovery that benzene has a molecule with a flat, regular six-layer structure, on the tops of which there are rotating carbon atoms, which are located in sp 2-hybrid system. A skin of six carbon atoms for the combination of three trigonal hybrid orbitals creates two σ - a binder of dried coals and another binder of water. All these ties are woven in the same area under cut 120 one to one. Hybridization suffers a fate of less than two in three R-electrons of carbon atoms Tom after illumination σ - the skin ligaments lose one more of the six benzene rings R-electron. In the history of the discovery of benzene, which stretched over more than a decade, one can see how important it was to make its way to the discovery that R-Electronics overlap one by one, not only in pairs with light π -zv'yazkov. For deyakih furnishings mozhlive perekrittya hmar R- electrons both from the right-handed side and from the evil side

This is possible because the molecule has a cyclic structure, and between the carbons there are new axes. R-electrons parallel to each other. The rest of the brain is adjusted because the molecule is flat.

Behind this, the molecules of benzene and carbon atoms are connected to each other by unusual and subordinate bonds. These ligaments, which were equal to everything, would have been brought up to “one and a half”. We will not guess that, based on the results of X-ray structural analysis of crystalline benzene, all the carbon-carbon bonds in benzene have a maximum density of 0.14 nm, which is intermediate between simple (0.154 nm) and intermediate (0.154 nm). 0.134 nm) in bonds.

In this manner, according to the current manifestations Benzene does not have typical sublinks between carbons. Well, as a result of this, it is necessary to recognize the manifestations of the authorities associated with subordinate connections. At that very hour it is not possible to sense the significant non-intensification of the benzene molecule. A cycloalkane with six carbons (cyclohexane) contains 12 water atoms, while benzene has 6 in total. like cyclotriene. In fact, benzene added by the reaction adds three molecules of water, halogens and ozone.

Currently, the scientific and technical literature has two graphic images of benzene

One is the non-saturated character of benzene, the other is its aromaticity.

How can we bind the benzene with its characteristic powers, its superior rank, and its aromatic character? Why does benzene exhibit unique thermodynamic stability?

It was recently shown that alkenes can easily add a water molecule and transform into alkane. This reaction occurs in the presence of heat, approximately 125.61 kJ per skin ligament, and is associated with the heat of hydration. Let's try to determine the heat of hydrogenation by estimating the thermodynamic stability of benzene.

In fact, the basic cyclohexene, cyclohexadiene and benzene are hydrogenated into cyclohexane

The heat of hydrogenation of cyclohexene was 119.75 kJ. Then the calculated value for cyclohexadiene may become 119.75 x 2 = 239.50 kJ (actually 231.96 kJ). If benzene contains three sub-links (cyclohexatriene Kekule), then the heat of hydration for the new one is small 119.75 x 3 = 359.25 kJ. The experimental significance in the remaining phase is different from what has been studied. When hydrogenating benzene, an additional 208.51 kJ of heat is seen, which is less than the estimated value by 359.25 - 208.51 = 150.73 kJ. This energy rings energy resonance. However, when benzene is hydrated, there is 150.73 kJ less energy than the calculated value, which means that benzene itself already contains 150.73 kJ less energy, a lower hypothetical cycle eksatrien. It is clear that benzene cannot be the mother of cyclohexatriene. The stability of the benzene molecule by the magnitude of the resonance energy is the result of the presence of isolated sublinks in it and the presence of a single electronic chlorine sextet R-electrons.

Given the benefits of its high thermodynamic stability, benzene does not preserve this stability during chemical reactions. It appears that this can only be achieved by saving the mind during the chemical reaction of the benzene ring in a stable manner. This ability is provided only by a substitution reaction, and therefore, for semi-aromatic series, a substitution reaction is more characteristic, not an addition reaction. During the electrophilic addition reaction, the aromatic compound ceases to be aromatic and loses its stability at the same time as resonance energy, which reduces this stability. For these reasons, aromatic properties occur in the addition reaction in a more complex manner, for example, alkenes. Another peculiarity of the reaction associated with the participation of aromatic compounds is its uncompromising nature. The stench will either enter into the reaction of adsorption, or it will immediately add up to everything. Please note that it is not possible to separate the products of partial hydrogenation or chlorination from benzene. As the reactions proceed, they proceed in such a manner that the products of continuous hydrogenation or chlorination immediately emerge

Such a development of connections with this that one electronic gloom of six R-Electrons in benzene are either active or not, intermediate options for a new shutdown.

Aromatic carbohydrates (arenes)

Representatives of aromatic carbohydrates are benzene C 6 H 6 and their homologues may be cyclic. The stench can be either intense or unsaturated. Some substances similar to benzene give off a pleasant odor. For these reasons, their colossal historical name has been preserved - aromatic carbohydrates. Today there are a lot of speeches that can be traced back to aromatic carbohydrates. Benzene is a typical representative of aromatic carbohydrates, a molecule of which has six carbon atoms.

Experimental data show that the benzene molecule has 92.3% carbon, like the acetylene molecule. Also, the simplest formula for benzene is the same as for acetylene - CH. The strength of benzene steam in water is 39, and the weight of the benzene is 78 g (2D H = 2‣‣‣39). If the formula for benzene is true b CH, then the mass of the yogo molyachi is guilty of buti 13 r, and chi not 78 year. Also, a benzene molecule consists of six atoms of carbon and six atoms of water (78: 13 = 6), and its molecular formula is C 6 H b.

Experiments have shown that when the temperature increases and in the presence of catalysts, three molecules of water are added to the benzene molecule and cyclohexane is created. It turns out that benzene has a cyclic nature. In this case, experiments have shown that the bonds in the benzene molecule are equivalent.

According to recent findings, the benzene molecule at the carbon atom has one s- and two p-electronic substances hybridized. (sp 2 -hybridization), and one p-electronic hmara is unhybridized. All three hybridized electron particles, overlapping with hybridized carbon atoms of carbon and s-charcoal atoms of water, create three σ-bonds that are located in the same plane. Non-hybridized p-electronic particles of carbon atoms are spread perpendicularly to the area of ​​straight σ-bonds. These shadows also overlap one after another (Fig. 40).

Rice. 40. Budova benzene molecules

The cycle of the benzene molecule does not have three cross-links: the unhybridized p-electron of the first carbon atom overlaps with the unhybridized carbon

Since the electron strength of the benzene molecule is distributed evenly, it is more correct to represent the structural formula of benzene as a hexacutane with a stake in the middle. There are a lot of aromatic carbohydrates similar to benzene - homologs of benzene. Combination of carbon and water, in molecules that have a benzene ring or a core, is brought to aromatic carbohydrates . Today's formula I (Friedrich Kekule (1829-1896) born 1865) or III. Radical -З 6 Н 5 is commonly called phenyl.

Budova molecules of benzene - understandable and visible. Classification and features of the category "Benzene benzene molecule" 2017, 2018.