Classification and nomenclature of organic substances (trivial and international). Classification and nomenclature of organic substances (trivial and international) Acids and their properties
Heteroorganic compounds (sulfur-, oxygen- and nitrogen-containing) of various structures and molecular weights are present in various proportions in distillate and residual fractions of oil. It is especially difficult to study the nature and composition of high-molecular heteroorganic compounds, the main part of which are resin-asphaltene substances. Thanks to lone pairs of electrons, heteroatoms of sulfur, oxygen and nitrogen are able to act as a coordinating center in the formation of associates in petroleum systems.
Sulfur compounds belong to the most representative group of heteroatomic components of gas condensate and oil systems. The total sulfur content in oil and gas systems varies widely: from hundredths of a percent to 6-8% (wt.) or more. A high content of total sulfur is typical for gas condensates of the Astrakhan, Karachaganak (0.9%) and other fields. The content of sulfur-containing compounds in some oils reaches 40% (wt.) and higher, in some cases the oil consists almost entirely of them. Unlike other heteroatoms, which are predominantly concentrated in CAB, a significant proportion of sulfur is contained in the distillate fractions. As a rule, the sulfur content in straight-run fractions increases as their boiling point and the total sulfur content of the original oil increase.
Minor amounts of inorganic sulfur-containing compounds (elemental sulfur and hydrogen sulfide) are present in oil and gas systems; they can also be formed as secondary products of the decomposition of other sulfur-containing compounds at high temperatures during distillation and destructive processing processes. Among the sulfur-containing compounds found in oil, the following have been identified (according to the Institute of Petroleum Chemistry, Tbilisi Branch, Siberian Branch, Russian Academy of Sciences).
1. Aliphatic, alicyclic and aromatic thiols (mercaptans) R-SH:
C 6 H 5 C n H 2 n +1 SH C n H 2 n +1 C 6 H 5 SH C 10 H 7 SH
arenoalkanothiols thionaphthols
2. Thioesters (sulfides) of the following main types:
R-S-R" C 6 H 5 -S-C 6 H 5
thiaalkanes, thiaalkenes, thiaalkynes diaryl sulfides
thiacycloalkanes alkylaryl sulfides arylthiaalkanes
(R, R" - saturated and unsaturated aliphatic hydrocarbon substituents).
3. Dialkyl disulfides R-S-S-R", where R, R" are alkyl, cycloalkyl or aryl substituents.
4. Thiophenes and their derivatives, the most important of which are the following arenotiophenes:
alkylbenzothiophenes alkylbenzonephthothiophenes alkyldibenzothiophenes
The distribution of various groups of sulfur-containing compounds in oils and in oil fractions is subject to the following patterns.
Thiols are found in almost all crude oils, usually in small concentrations and constitute 2-10% (wt.) of the total content of sulfur-containing compounds. Gas condensates contain mainly aliphatic mercaptans C 1 -C h. Some oils and gas condensates and their fractions are natural concentrates of mercaptans, examples of which are the gasoline fractions of the super-giant Caspian field; fraction 40-200°C of gas condensate from the Orenburg field, containing 1.24% (wt.) of total sulfur, including 0.97% mercaptan; light kerosene fraction 120-280°C of Tengiz oil, containing 45-70% mercaptan sulfur of the total content of sulfur-containing compounds. At the same time, the reserves of natural thiols in the hydrocarbon raw materials of the Caspian region correspond to the level of their global production by synthetic means. Natural thiols are promising raw materials for the synthesis of pesticides (based on symmetric triazines) and the odorization of liquefied gases. Russia's prospective demand for thiols for odorization is currently 6 thousand tons/year.
Thioesters make up up to 27% of the amount of sulfur-containing compounds in crude oils and up to 50% in middle fractions; in heavy vacuum gas oils the sulfide content is lower. Methods for isolating petroleum sulfides are based on their ability to form complex compounds of the donor-acceptor type due to the transfer of the lone pair of electrons of the sulfur atom to the free orbital of the acceptor. Metal halides, haloalkyl, and halogens can act as electron acceptors. Complexation reactions with petroleum sulfides, unfortunately, do not proceed selectively; Other heteroatomic components of oil may also take part in the formation of complexes.
Dialkyl disulfides have not been found in crude oils; they are usually formed during the oxidation of mercaptans under mild conditions and are therefore present in gasoline (up to 15%). The main share of sulfur-containing compounds in oils is the so-called “residual” sulfur, which is not determined by standard methods. Its composition is dominated by thiophenes and their derivatives, so previously “residual” sulfur was called “thiophene”, but using negative ion mass spectrometry, previously undetected sulfoxides, sulfones and disulfane were discovered in it. In gasoline fractions the content of thiophene derivatives is low; in medium and especially high-boiling fractions it reaches 50-80% of the total sulfur-containing compounds. The relative content of thiophene derivatives, as a rule, coincides with the degree of aromaticity of the petroleum system. Difficulties that arise when isolating sulfur-containing compounds (especially from high-boiling fractions) are caused by the similarity of the chemical properties of arenes and thiophenes. The similarity of their chemical behavior is due to the aromaticity of thiophenes, which arises as a result of the inclusion of a sulfur heteroatom in the π-electron system before the aromatic sextet. The consequence of this is the increased tendency of petroleum thiophenes to undergo intense intermolecular interactions.
Oxygen-containing compounds contained in oil systems from 0.1-1.0 to 3.6% (wt.). With an increase in the boiling point of distillate fractions, their content increases, and the main part of the oxygen is concentrated in resin-asphaltene substances. Oils and distillates contain up to 20% or more oxygen-containing compounds.
Among them, substances of an acidic and neutral nature are traditionally distinguished. Acid components include carboxylic acids and phenols. Neutral oxygen-containing compounds are represented by ketones, acid anhydrides and amides, esters, furan derivatives, alcohols and lactones.
The presence of acids in oils was discovered a long time ago due to their high chemical activity compared to hydrocarbons. The history of their discovery in oil is as follows. When producing high-quality kerosene for lighting purposes, it was treated with alkali (acid-base purification) and the formation of substances with high emulsifying ability was observed. Subsequently, it turned out that emulsifiers are sodium salts of acids contained in distillate fractions. Extraction with aqueous and alcoholic solutions of alkalis is still a classic method for extracting acidic components from oils. Currently, methods for isolating acids and phenols are also based on the interaction of their functional groups (carboxyl and hydroxyl) with some reagent.
Carboxylic acids are the most studied class of oxygen-containing petroleum compounds. The content of petroleum acids by fraction varies according to an extreme dependence, the maximum of which, as a rule, falls on light and medium oil fractions. Various types of petroleum acids were identified using chromatography-mass spectrometry. Most of them are monobasic (RCOOH), where R can be almost any fragment of hydrocarbon and heteroorganic petroleum compounds. It has long been noted that the group compositions of acids and oils correspond to each other: aliphatic acids predominate in methane oils, naphthenic and naphthenoaromatic acids predominate in naphthenic oils. Aliphatic acids from C 1 to C 25 with a linear structure and some with a branched structure were discovered. Moreover, in petroleum acids the ratio of n-alkanoic and branched acids coincides with the ratio of the corresponding hydrocarbons in oils.
Aliphatic acids are represented primarily by n-alkanoic acids. Of the branched acids, those containing a methyl substituent in the main chain are more common. All lower isomers of this type are found in oils, up to C7. Another important group of aliphatic acids are acids of isoprenoid structure, among which pristanic (C 19) and phytanic (C 20) predominate.
Alicyclic (naphthenic) petroleum acids are monocyclocarboxylic acids - derivatives of cyclopentane and cyclohexane; polycyclic ones can contain up to 5 rings (data for Californian oil). COOH groups in monocyclic acid molecules are directly connected to the ring or are located at the end of aliphatic substituents. There can be up to three (most often methyl) substituents in a ring, the most common positions of which are 1, 2; 13; 1, 2, 4; 1, 1, 3 and 1, 1, 2, 3.
Molecules of tri-, tetra- and pentacyclic acids isolated from oils are constructed mainly from cyclohexane rings condensed together.
The presence of hexacyclic naphthenic acids with cyclohexane rings in oils has been established. Aromatic acids in oils are represented by benzoic acid and its derivatives. Many homologous series of polycyclic naphthenoaromatic acids were discovered in oils, and monoaromatic steroid acids were identified in Samotlor oil
Of oxygen-containing compounds, petroleum acids are characterized by the highest surface activity. It has been established that the surface activity of both low-resin and high-resin oils decreases significantly after removing acidic components (acids and phenols) from them. Strong acids take part in the formation of oil associates, as shown by studying their rheological properties.
Phenols have been studied much worse than acids. Their content in oils from West Siberian fields ranges from 40 to 900 mg/l. In West Siberian oils, the concentrations of phenols increase in the order C 6<С 7 << С 8 <С 9 . В нефтях обнаружены фенол, все крезолы, ксиленолы и отдельные изомеры С 9 . Установлено, что соотношение между фенолами и алкилфенолами колеблется в пределах от 1: (0,3-0,4) до 1: (350-560) и зависит от глубины залегания и возраста нефти. В некоторых нефтях идентифицирован β-нафтол. Высказано предположение о наличии соединений типа о-фенилфенолов, находящихся в нефтях в связанном состоянии из-за склонности к образованию внутримолекулярных водородных связей. При исследовании антиокислительной способности компонентов гетероор-ганических соединений нефти установлено, что концентраты фенольных соединений являются наиболее активными природными ингибиторами.
In neutral oxygen-containing compounds of Californian oils, all the simplest alkyl ketones C3-C6, acetophenone and its naphtheno- and arene-derivatives, fluorenone and its closest homologues were found. The yield of ketone concentrate from Samotlor oil, consisting mainly of dialkyl ketones, is 0.36%, while the degree of ketone extraction is only 20%, which indicates the presence of ketones of large molecular weights that cannot be extracted using this method. When studying ketones in Western Siberian oils, it was found that they contain C 19 -C3 2 ketones, with aliphatic ketones predominating in methane oils, and with cyclane and aromatic substituents in naphthenic oils.
It can be assumed that oils contain alcohols in a free state; when bound, they form part of esters. Of the heteroorganic petroleum compounds, the tendency of oxygen-containing compounds to undergo intense intermolecular interactions is the most studied.
The study of nitrogen-containing compounds is possible in two ways - directly in crude oil and after their isolation and separation. The first way makes it possible to study nitrogen-containing compounds in a state close to natural, however, it is possible that noticeable errors may occur due to the low concentration of these compounds. The second way makes it possible to reduce such errors, but in the process of chemical exposure to oil during separation and isolation, a change in their structure is possible. It has been established that nitrogen-containing compounds in oil are represented predominantly by cyclic compounds. Aliphatic nitrogen-containing compounds are found only in products of destructive oil refining, in which they are formed as a result of the destruction of nitrogen heterocycles.
All nitrogen-containing petroleum compounds are, as a rule, functional derivatives of arenes, and therefore have a molecular weight distribution similar to them. However, unlike arenes, nitrogen-containing compounds are concentrated in high-boiling oil fractions and are an integral part of CAB. Up to 95% of the nitrogen atoms present in oil are concentrated in resins and asphaltenes. It has been suggested that during the isolation of resins and asphaltenes, even relatively low molecular weight nitrogen-containing compounds coprecipitate with them in the form of donor-acceptor complexes.
In accordance with the generally accepted acid-base classification nitrogen-containing compounds are dividedon nitrogenous bases and neutral compounds.
Nitrogen-containing bases are, apparently, the only carriers of basic properties among the components of petroleum systems. The proportion of nitrogen-containing bases in oil titrated with perchloric acid in an acetic acid medium ranges from 10 to 50%. Currently, more than 100 alkyl- and arene-condensed analogues of pyridine, quinoline and other bases have been identified in oils and petroleum products.
Strongly basic nitrogen-containing compounds are represented by pyridines and their derivatives:
Weakly basic nitrogen-containing compounds include anilines, amides, imides and N-cycloalkyl derivatives that have alkyl, cycloalkyl and phenyl groups as substituents on the pyrrole ring:
Neutral nitrogen-containing compounds that do not contain heteroatoms other than the nitrogen atom in their molecules and are isolated from oil include indoles, carbazoles and their naphthenic and sulfur-containing derivatives:
When isolated, neutral nitrogen-containing compounds form associates with oxygen-containing compounds and are extracted along with nitrogen-containing bases.
Along with the mentioned monofunctional ones, the following nitrogen-containing compounds have been identified in oils:
1. Polyaromatic with two nitrogen atoms in the molecule:
2. Compounds with two heteroatoms (nitrogen and sulfur) in one ring - thiazoles and benzothiazoles and their alkyl- and naphthenic homologues:
3. Compounds with two heteroatoms of nitrogen and sulfur in different rings: thiophene-containing alkyl-, cycloalkylindoles and carbazoles.
4. Compounds with a carbonyl group in a nitrogen-containing heterocycle, such as piperidones and quinolones:
5. Porphyrins. The structure of porphyrins, which are complex compounds with vanadyl VO, nickel and iron, will be discussed below.
The importance of nitrogen-containing petroleum compounds as natural surfactants is very great; they, along with CAB, largely determine the surface activity at liquid interfaces and the wetting ability of oil at the rock-oil, metal-oil interfaces. Nitrogen-containing compounds and their derivatives - pyridines, hydroxypyridines, quinolines, hydroxyquinolines, imidazolines, oxazolines, etc. - are natural oil-soluble surfactants that have inhibitory properties against metal corrosion during oil production, transportation and refining. Such nitrogen-containing petroleum compounds as homologues of pyrrole, indole, carbazole, thiazoles and amides are characterized by weaker surface-active properties.
Resin-asphaltenic substances (CAB). One of the most representative groups of heteroorganic high molecular weight petroleum compounds is CAB. The characteristic features of CAB - significant molecular weights, the presence of various heteroelements in their composition, polarity, paramagnetism, high propensity for magnetic resonance and association, polydispersity and the manifestation of pronounced colloidal-disperse properties - contributed to the fact that the methods usually used in analysis turned out to be unsuitable for their study low boiling components. Taking into account the specifics of the object being studied, Sergienko S.R. more than 30 years ago, he singled out the chemistry of high-molecular petroleum compounds as an independent branch of petroleum chemistry and made a major contribution to its development with his fundamental works.
Until the 60-70s, researchers determined the physicochemical characteristics of CAB (some of them are given in Table 2.4) and tried to present the structural formula of the average molecule of asphaltenes and resins based on instrumental structural analysis data.
Similar attempts are being made today. The values of elemental composition, average molecular weights, density, solubility, etc. for CAB samples of various domestic and foreign oils, varying within significant limits, reflect the diversity of natural oils. Most of the heteroelements present in oil and almost all metals are concentrated in resins and asphaltenes.
The nitrogen in CAB is predominantly found in heteroaromatic moieties of the pyridine (basic), pyrrole (neutral) and porphyrin (metal complex) types. Sulfur is part of heterocycles (thiophene, thiacyclane, thiazole), thiol groups and sulfide bridges that cross-link molecules. Oxygen in resins and asphaltenes is presented in the form of hydroxyl (phenolic, alcoholic), carboxyl, ether (simple, complex lactone), carbonyl (ketone, quinone) groups and furan rings. There is a certain correspondence between the molecular weight of asphaltenes and the content of heteroelements (Fig. 2.2).
Let us characterize the current level of ideas about CAB. Yen notes the universal nature of asphaltenes as a constituent of natural carbon sources, not only caustobiolites (petroles and solid fuels), but also sedimentary rocks and meteorites.
According to the classification of natural resources with a hydrocarbon base, proposed by Abraham, oils include those that contain up to 35-40% (wt.) CAB, and natural asphalts and bitumens contain up to 60-75% (wt.) CAB, according to other data - up to 42-81%. In contrast to the lighter components of oil, the criterion for classifying them into their groups was the similarity of their chemical structure, the criterion for combining compounds into a class called CAB is their similarity in solubility in a particular solvent. When oil and oil residues are exposed to large quantities of petroleum ether and low-boiling alkanes, substances called asphaltenes, which are soluble in lower arenes, and solvation of other components - maltenes, consisting of a hydrocarbon part and resins.
Modern heavy oil separation schemes are based on classical techniques first proposed by Markusson. Substances insoluble in carbon disulfide and other solvents are classified as carboids. Substances that are soluble only in carbon disulfide and precipitated by carbon tetrachloride are called carbenes. Carboids and carbenes, as a rule, are found in the composition of heavy products of destructive oil refining in an amount of several percent and will be discussed separately below. They are practically absent in the composition of crude oils and in the residues of primary oil refining.
The properties of the isolated asphaltenes also depend on the solvent. A consequence of the differences in the nature and properties of solvents is that the molecular weight of asphaltenes from Arab oils when dissolved in benzene is on average 2 times higher than in tetrahydrofuran. (Table 2. 5).
Table 2.5
Solvent Solvent parameter Dielectric Dipole moment, Dpermeability permeability
Tetrahydrofuran 9.1 7.58 1,75 Benzene 9.2 2.27 0
In the process of developing ideas about the structure and nature of petroleum CABs, two main stages can be distinguished, connected by the general idea of a colloidal-disperse structure, but differing in the methodological approach to assessing the structure of a single element of the colloidal structure. At the first stage - the stage of chemical ideas about the structure of CAB molecules - a standard chemical approach was used to identify the structure of an unknown compound. After establishing the molecular weight, elemental composition and gross formula of the molecules of resins and asphaltenes, C n H 2 n - z N p S g O r . The z value was then calculated. For resins it was 40-50, for asphaltenes - 130-140. A typical example of the results of such studies for CAB samples of various domestic and foreign oils is presented in Table. 2.4. (see table 1.4). As can be seen, asphaltenes differ from resins from the same source by a higher content of carbon and metals and a lower proportion of hydrogen, larger sizes of polyaromatic cores, as well as a shorter average length of large aliphatic substituents and a smaller number of acyclic fragments directly condensed with aromatic cores.
The second stage can be characterized as the stage of development of physical ideas about the structure of asphaltenes and analysis of the reasons that determine the tendency of asphaltenes to associate. Indeed, an explanation of the dependence of molecular weight on the determination conditions (see Table 2.5), as well as its linear dependence on the size of asphaltenes particles (Fig. 1.5), became possible within the framework of qualitatively new ideas about the structure of asphaltenes.
In 1961 T. Yen proposed the so-called stack model of the structure of asphaltenes of the “plate to plate” type. The model was based not on the need for it to correspond to the calculated structural parameters of the composition of asphaltenes, but on the fundamental possibility of plane parallel orientation of polyaromatic fragments of different molecules. Their combination as a result of intermolecular (π - π, donor-acceptor, etc.) interactions occurs with the formation of layered stacking structures (the term “stacking” is adopted in molecular biology to denote a stack-like arrangement of molecules one above the other).
Rice. 2.5. Correlation between asphaltenes particle size (D) and their molecular weight (M)
According to Yen's model based on X-ray diffraction data, asphaltenes have a crystalline structure and are stacking structures with a diameter of 0.9-1.7 nm of 4-5 layers spaced 0.36 nm apart. The size of stacking structures normal to the plane of aromatic plates is 1.6-2.0 nm (Fig. 2.6). Straight lines show flat polyaromatic molecules, and broken lines show saturated fragments of molecules. Polyaromatic fragments are represented by relatively small, most often no more than tetracyclic, nuclei. Of the aliphatic fragments, the most common are short alkyl groups C 1 -C 5, primarily methyl, but linear branched alkanes containing 10 carbon atoms or more are also present. CAB molecules also contain polycyclic saturated structures with 1-5 condensed rings, mainly bicyclanes.
Within the framework of Yen's model, the above-mentioned dependence of the molecular weight of asphaltenes on the conditions of isolation and the nature of the solvent is easily explained by an association that assumes several levels of structural organization of asphaltenes: a molecularly dispersed state (I), in which asphaltenes are found in the form of separate layers; colloidal state (II), which is the result of the formation of stacking structures with characteristic sizes; a dispersed kinetically stable state (III), which arises during aggregation of stacking structures, and a dispersed kinetically unstable state (IV), accompanied by the release of a precipitate.
Rice. 2.6. Jen's model of the structure of asphaltenes
Many modern researchers adhere to the pack structure model of asphaltene structure. Unger F.G. expressed an original point of view on the process of the emergence and existence of CAB in oil. Oils and oil systems containing CAB, in his opinion, are thermodynamically labile paramagnetic associated solutions. The cores of associates of such solutions are formed by asphaltenes, in which stable free radicals are localized, and the solvation layers surrounding the cores consist of diamagnetic resin molecules. Some diamagnetic resin molecules are capable of transitioning to an excited triplet state and undergoing hemolysis. Therefore, resins are a potential source of asphaltenes, which explains what was noted by L.G. Gurvich. ease of transformation of resins into asphaltenes.
So, the novelty of the presented ideas is associated with the affirmation of the special role of exchange interactions in explaining the nature of CAB. In contrast to the burst model, the idea of a centrally symmetric structure of the CAB particle is being developed. It was first postulated by D. Pfeiffer and R. Saal, who proposed a static model for the structure of the structural unit of asphaltenes. According to it, the core of the structural unit is formed by high molecular weight polycyclic hydrocarbons and is surrounded by components with a gradually decreasing degree of aromaticity. Neumann G. emphasized that it is energetically beneficial to turn polar groups into the structural unit, and hydrocarbon radicals outward, which is in agreement with the rule of polarity equalization according to Rehbinder.
Porphyrins are typical examples of native petroleum complex compounds. Porphyrins with vanadium as a coordination center (in the form of vanadyl) or nickel (see 11). Petroleum vanadyl porphyrins are mainly homologues of two series: alkyl-substituted porphyrins with different total numbers of carbon atoms in the side substituents of the porphin ring and porphyrins with an additional cyclopentene ring. Metal porphyrin complexes are present in natural bitumens up to 1 mg/100 g, and in high-viscosity oils - up to 20 mg/100 g of oil. When studying the nature of the distribution of metal porphyrin complexes between the constituent parts of VAT using extraction and gel chromatography methods, it was found that 40% of vanadyl porphyrins are concentrated in dispersed particles (approximately equally in the composition of the core and solvation layer), and the rest of them and nickel porphyrins are contained in the dispersed environment.
Vanadyl porphyrins in asphaltenes make a significant contribution to the surface activity of oils, while the intrinsic surface activity of asphaltenes is low. Thus, a study of oils from Bashkiria showed that the surface tension of oils at the interface with water strongly correlates with the content of vanadyl porphyrins in them, while the correlation coefficient with the content of asphaltenes in them is relatively low (Fig. 2.7).
The influence of metalporphyrins on the dispersed structure of oil and the conditions for phase transitions in oil systems has been studied to a lesser extent. There is evidence of their negative impact, along with other heteroatomic components, on catalytic processes of oil refining. In addition, they should strongly influence the kinetics and mechanism of phase transitions in the SSS.
Rice. 2.7. Isotherms of interfacial tension a at the boundary with water:
a - benzene solutions of asphaltenes: 1- asphaltenes with porphyrins; 2-5 - asphaltenes as porphyrins are removed after one, five, seven, thirteen extractions, respectively; b - oils of Bashkiria
One of the most common chemical elements found in the vast majority of chemicals is oxygen. Oxides, acids, bases, alcohols, phenols and other oxygen-containing compounds are studied in the course of inorganic and organic chemistry. In our article we will study the properties and also give examples of their use in industry, agriculture and medicine.
Oxides
The simplest in structure are binary compounds of metals and nonmetals with oxygen. The classification of oxides includes the following groups: acidic, basic, amphoteric and indifferent. The main criterion for the division of all these substances is which element combines with oxygen. If it is metal, then they are considered basic. For example: CuO, MgO, Na 2 O - oxides of copper, magnesium, sodium. Their main chemical property is their reaction with acids. So, copper oxide reacts with chloride acid:
CuO + 2HCl -> CuCl2 + H2O + 63.3 kJ.
The presence of atoms of non-metallic elements in the molecules of binary compounds indicates that they belong to acidic compounds: hydrogen H 2 O, carbon dioxide CO 2, phosphorus pentoxide P 2 O 5. The ability of such substances to react with alkalis is their main chemical characteristic.
As a result of the reaction, species can be formed: acidic or medium. This will depend on how many moles of alkali are reacting:
- CO2 + KOH => KHCO3;
- CO2+ 2KOH => K2CO3 + H2O.
Another group of oxygen-containing compounds, which includes chemical elements such as zinc or aluminum, are classified as amphoteric oxides. Their properties show a tendency towards chemical interaction with both acids and alkalis. The products of the interaction of acid oxides with water are acids. For example, in the reaction of sulfuric anhydride and water, acids are formed - this is one of the most important classes of oxygen-containing compounds.
Acids and their properties
Compounds consisting of hydrogen atoms bonded to complex ions of acidic residues are acids. Conventionally, they can be divided into inorganic, for example, carbonate acid, sulfate, nitrate, and organic compounds. The latter include acetic acid, formic acid, and oleic acid. Both groups of substances have similar properties. Thus, they enter into a neutralization reaction with bases, react with salts and basic oxides. Almost all oxygen-containing acids in aqueous solutions dissociate into ions, being conductors of the second kind. The acidic nature of their environment, caused by the excessive presence of hydrogen ions, can be determined using indicators. For example, violet litmus turns red when added to an acid solution. A typical representative of organic compounds is acetic acid containing a carboxyl group. It contains a hydrogen atom, which causes acidity. It is a colorless liquid with a specific pungent odor, crystallizing at temperatures below 17 ° C. CH 3 COOH, like other oxygen-containing acids, is perfectly soluble in water in any proportions. Its 3 - 5% solution is known in everyday life as vinegar, which is used in cooking as a seasoning. The substance has also found its use in the production of silk acetate, dyes, plastics and some medicines.
Organic compounds containing oxygen
In chemistry, one can distinguish a large group of substances that contain, in addition to carbon and hydrogen, also oxygen particles. These are carboxylic acids, esters, aldehydes, alcohols and phenols. All their chemical properties are determined by the presence of special complexes in the molecules - functional groups. For example, an alcohol containing only limiting bonds between atoms - ROH, where R is a hydrocarbon radical. These compounds are usually considered to be derivatives of alkanes in which one hydrogen atom is replaced by a hydroxo group.
Physical and chemical properties of alcohols
The physical state of alcohols is liquids or solid compounds. There are no gaseous substances among alcohols, which can be explained by the formation of associates - groups consisting of several molecules connected by weak hydrogen bonds. This fact also determines the good solubility of lower alcohols in water. However, in aqueous solutions, oxygen-containing organic substances - alcohols - do not dissociate into ions, do not change the color of indicators, that is, they have a neutral reaction. The hydrogen atom of the functional group is weakly bonded to other particles, therefore, in chemical interactions it is able to leave the confines of the molecule. At the place of free valency, it is replaced by other atoms, for example, in reactions with active metals or with alkalis - by metal atoms. In the presence of catalysts, such as platinum mesh or copper, alcohols are oxidized by energetic oxidizing agents - potassium dichromate or permanganate, to aldehydes.
Esterification reaction
One of the most important chemical properties of oxygen-containing organic substances: alcohols and acids is the reaction leading to the production of esters. It is of great practical importance and is used industrially for the extraction of esters used as solvents in the food industry (in the form of fruit essences). In medicine, some of the esters are used as antispasmodics, for example, ethyl nitrite dilates peripheral blood vessels, and isoamyl nitrite protects coronary artery spasms. The equation for the esterification reaction is as follows:
CH3COOH+C2H5OH<--(H2SO4)-->CH3COOC2H5+H2O
In it, CH 3 COOH is acetic acid, and C 2 H 5 OH is the chemical formula of ethanol alcohol.
Aldehydes
If a compound contains the functional group -COH, then it is an aldehyde. They are represented as products of further oxidation of alcohols, for example, with oxidizing agents such as copper oxide.
The presence of a carbonyl complex in molecules of formic or acetaldehyde determines their ability to polymerize and attach atoms of other chemical elements. Qualitative reactions that can be used to prove the presence of a carbonyl group and that a substance is an aldehyde are the reaction of a silver mirror and interaction with copper hydroxide when heated:
The most widely used acetaldehyde is used in industry to produce acetic acid, a large-scale product of organic synthesis.
Properties of oxygen-containing organic compounds - carboxylic acids
The presence of a carboxyl group - one or more - is a distinctive feature of carboxylic acids. Due to the structure of the functional group, dimers can form in acid solutions. They are connected to each other by hydrogen bonds. The compounds dissociate into hydrogen cations and acidic anions and are weak electrolytes. An exception is the first representative of a series of saturated monobasic acids - formic, or methane, which is a conductor of the second kind of medium strength. The presence in molecules of only simple sigma bonds indicates that they are saturated, but if substances contain double pi bonds, these are unsaturated substances. The first group includes acids such as methane, acetic, and butyric. The second is represented by compounds that are part of liquid fats - oils, for example, oleic acid. The chemical properties of oxygen-containing compounds: organic and inorganic acids are largely similar. Thus, they can interact with active metals, their oxides, alkalis, and also with alcohols. For example, acetic acid reacts with sodium oxide to form a salt - sodium acetate:
NaOH + CH3COOH→NaCH3COO + H2O
A special place is occupied by compounds of higher carboxylic oxygen-containing acids: stearic and palmitic, with trihydric saturated alcohol - glycerol. They belong to esters and are called fats. These same acids are included in sodium and potassium salts as an acid residue, forming soaps.
Important organic compounds that are widespread in living nature and play a leading role as the most energy-intensive substance are fats. They are not an individual compound, but a mixture of dissimilar glycerides. These are compounds of saturated polyhydric alcohol - glycerol, which, like methanol and phenol, contains hydroxyl functional groups. Fats can be subjected to hydrolysis - heating with water in the presence of catalysts: alkalis, acids, zinc oxides, magnesium. The reaction products will be glycerin and various carboxylic acids, which are subsequently used for soap production. In order not to use expensive natural essential carboxylic acids in this process, they are obtained by oxidizing paraffin.
Phenols
Finishing our consideration of classes of oxygen-containing compounds, let’s focus on phenols. They are represented by a phenyl radical -C 6 H 5 connected to one or more functional hydroxyl groups. The simplest representative of this class is carbolic acid, or phenol. As a very weak acid, it can interact with alkalis and active metals - sodium, potassium. A substance with pronounced bactericidal properties - phenol - is used in medicine, as well as in the production of dyes and phenol-formaldehyde resins.
In our article, we studied the main classes of oxygen-containing compounds and also examined their chemical properties.
Test on the topic: “Oxygen-containing and nitrogen-containing organic substances” (grade 10)
Dear students, this test is the result of studying the topic “ Oxygen-containing and nitrogen-containing organic substances"and affects the marking for the trimester. You are given 40 minutes to complete it. When performing, it is prohibited to use the textbook, reference materials and Inttrnet.
I wish you success!
1. The hydrogen atom in the molecule has the greatest activity
2. Interact with each other
3. Don't interact between themselves
4. Acetic acid can react with either of the two substances
5. Are the following judgments about the properties of acetic acid true?
1.Acetic acid does not react with sodium carbonate.
2. Acetic acid solution conducts electric current.
6. Dehydration reaction is possible for
7. Sodium hydroxide will react with
9. The oxidation product of propanol cannot be
10. When 57.5 g of ethanol was heated with concentrated sulfuric acid, two organic compounds A and B were formed. Substance A, a gas, can decolorize 100 g of a 40% solution of bromine in carbon tetrachloride. Substance B is a low-boiling liquid. Determine the resulting compounds A and B, also calculate the volume of A (at zero) and the mass of B, assuming that ethanol has reacted completely.
| Verified Content | Testable skills |
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| Properties of substances | ||
| Properties of phenol | Ability to select one answer from four proposed options |
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| Properties of alcohols | Ability to select one answer from four proposed options |
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| Properties of organic acid | Ability to select one answer from four proposed options |
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| Properties of organic acid | Ability to select one answer from four proposed options |
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| Reactions of dehydration of organic substances | ||
| Properties of organic acids and phenol | Ability to conduct multiple choice |
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| Carrying out a chain of reactions | Ability to conduct multiple choice |
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| Properties of alcohols | Ability to conduct multiple choice |
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| Properties of alcohols | Ability to write down and solve problems |
Keys to the test
10. 5.6 l of ethene and 37 g of diethyl ether
It is known that the properties of organic substances are determined by their composition and chemical structure. Therefore, it is not surprising that the classification of organic compounds is based on the theory of structure - the theory of L. M. Butlerov. Organic substances are classified according to the presence and order of connection of atoms in their molecules. The most durable and least changeable part of an organic substance molecule is its skeleton - a chain of carbon atoms. Depending on the order of connection of carbon atoms in this chain, substances are divided into acyclic, which do not contain closed chains of carbon atoms in molecules, and carbocyclic, which contain such chains (cycles) in molecules.
In addition to carbon and hydrogen atoms, molecules of organic substances can contain atoms of other chemical elements. Substances in whose molecules these so-called heteroatoms are included in a closed chain are classified as heterocyclic compounds.
Heteroatoms (oxygen, nitrogen, etc.) can be part of molecules and acyclic compounds, forming functional groups in them, for example, hydroxyl - OH, carbonyl, carboxyl, amino group -NH2.
Functional group- a group of atoms that determines the most characteristic chemical properties of a substance and its belonging to a certain class of compounds. 
Hydrocarbons- These are compounds consisting only of hydrogen and carbon atoms.
Depending on the structure of the carbon chain, organic compounds are divided into open-chain compounds - acyclic (aliphatic) and cyclic- with a closed chain of atoms.
Cyclic ones are divided into two groups: carbocyclic compounds(cycles are formed only by carbon atoms) and heterocyclic(the cycles also include other atoms, such as oxygen, nitrogen, sulfur).
Carbocyclic compounds, in turn, include two series of compounds: alicyclic and aromatic.
Aromatic compounds, based on the structure of their molecules, have flat carbon-containing rings with a special closed system of p-electrons, forming a common π-system (a single π-electron cloud). Aromaticity is also characteristic of many heterocyclic compounds.
All other carbocyclic compounds belong to the alicyclic series.
Both acyclic (aliphatic) and cyclic hydrocarbons can contain multiple (double or triple) bonds. Such hydrocarbons are called unsaturated (unsaturated) in contrast to saturated (saturated), containing only single bonds.
Saturated aliphatic hydrocarbons called alkanes, they have the general formula C n H 2 n +2, where n is the number of carbon atoms. Their old name is often used today - paraffins.
Containing one double bond, got the name alkenes. They have the general formula C n H 2 n.
Unsaturated aliphatic hydrocarbonswith two double bonds called alkadienes
Unsaturated aliphatic hydrocarbonswith one triple bond called alkynes. Their general formula is C n H 2 n - 2.
Saturated alicyclic hydrocarbons - cycloalkanes, their general formula is C n H 2 n.
A special group of hydrocarbons, aromatic, or arenas(with a closed common π-electron system), known from the example of hydrocarbons with the general formula C n H 2 n -6.
Thus, if in their molecules one or more hydrogen atoms are replaced by other atoms or groups of atoms (halogens, hydroxyl groups, amino groups, etc.), hydrocarbon derivatives: halogen derivatives, oxygen-containing, nitrogen-containing and other organic compounds.
Halogen derivatives hydrocarbons can be considered as products of the replacement of one or more hydrogen atoms in hydrocarbons by halogen atoms. In accordance with this, saturated and unsaturated mono-, di-, tri- (in the general case poly-) halogen derivatives can exist.
General formula of monohalogen derivatives of saturated hydrocarbons:
and the composition is expressed by the formula
C n H 2 n +1 G,
where R is the remainder of a saturated hydrocarbon (alkane), a hydrocarbon radical (this designation is used further when considering other classes of organic substances), G is a halogen atom (F, Cl, Br, I).
Alcohols- derivatives of hydrocarbons in which one or more hydrogen atoms are replaced by hydroxyl groups.
Alcohols are called monatomic, if they have one hydroxyl group, and limiting if they are derivatives of alkanes.
General formula of saturated monohydric alcohols:
and their composition is expressed by the general formula:
C n H 2 n +1 OH or C n H 2 n +2 O
There are known examples of polyhydric alcohols, that is, those with several hydroxyl groups.
Phenols- derivatives of aromatic hydrocarbons (benzene series), in which one or more hydrogen atoms in the benzene ring are replaced by hydroxyl groups.
The simplest representative with the formula C 6 H 5 OH is called phenol.
Aldehydes and ketones- derivatives of hydrocarbons containing a carbonyl group of atoms (carbonyl).
In aldehyde molecules, one carbonyl bond connects with a hydrogen atom, the other with a hydrocarbon radical.
In the case of ketones, the carbonyl group is bonded to two (generally different) radicals.
The composition of saturated aldehydes and ketones is expressed by the formula C n H 2l O.
Carboxylic acids- hydrocarbon derivatives containing carboxyl groups (-COOH).
If there is one carboxyl group in an acid molecule, then the carboxylic acid is monobasic. General formula of saturated monobasic acids (R-COOH). Their composition is expressed by the formula C n H 2 n O 2.
Ethers are organic substances containing two hydrocarbon radicals connected by an oxygen atom: R-O-R or R 1 -O-R 2.
Radicals can be the same or different. The composition of ethers is expressed by the formula C n H 2 n +2 O
Esters- compounds formed by replacing the hydrogen atom of the carboxyl group in carboxylic acids with a hydrocarbon radical.
Nitro compounds- derivatives of hydrocarbons in which one or more hydrogen atoms are replaced by a nitro group -NO 2.
General formula of saturated mononitro compounds:
and the composition is expressed by the general formula
C n H 2 n +1 NO 2 .
Amines- compounds that are considered as derivatives of ammonia (NH 3), in which hydrogen atoms are replaced by hydrocarbon radicals.
Depending on the nature of the radical, amines can be aliphaticand aromatic.
Depending on the number of hydrogen atoms replaced by radicals, the following are distinguished:
Primary amines with the general formula: R-NNH 2
Secondary - with the general formula: R 1 -NН-R 2
Tertiary - with the general formula:
In a particular case, secondary and tertiary amines may have the same radicals.
Primary amines can also be considered as derivatives of hydrocarbons (alkanes), in which one hydrogen atom is replaced by an amino group -NH 2. The composition of saturated primary amines is expressed by the formula C n H 2 n +3 N.
Amino acids contain two functional groups connected to a hydrocarbon radical: an amino group -NH 2, and a carboxyl -COOH.
The composition of saturated amino acids containing one amino group and one carboxyl is expressed by the formula C n H 2 n +1 NO 2.
Other important organic compounds are known that have several different or identical functional groups, long linear chains connected to benzene rings. In such cases, a strict determination of whether a substance belongs to a specific class is impossible. These compounds are often classified into specific groups of substances: carbohydrates, proteins, nucleic acids, antibiotics, alkaloids, etc.
To name organic compounds, two nomenclatures are used: rational and systematic (IUPAC) and trivial names.
Compilation of names according to IUPAC nomenclature
1) The name of the compound is based on the root of the word, denoting a saturated hydrocarbon with the same number of atoms as the main chain.
2) A suffix is added to the root, characterizing the degree of saturation:
An (ultimate, no multiple connections);
-ene (in the presence of a double bond);
-in (in the presence of a triple bond).
If there are several multiple bonds, then the suffix indicates the number of such bonds (-diene, -triene, etc.), and after the suffix the position of the multiple bond must be indicated in numbers, for example:
CH 3 –CH 2 –CH=CH 2 CH 3 –CH=CH–CH 3
butene-1 butene-2
CH 2 =CH–CH=CH2
butadiene-1,3
Groups such as nitro-, halogens, hydrocarbon radicals that are not included in the main chain are placed in the prefix. They are listed in alphabetical order. The position of the substituent is indicated by the number before the prefix.
The order of naming is as follows:
1. Find the longest chain of C atoms.
2. Number the carbon atoms of the main chain sequentially, starting from the end closest to the branch.
3. The name of the alkane is composed of the names of the side radicals, listed in alphabetical order, indicating the position in the main chain, and the name of the main chain.
Nomenclature of some organic substances (trivial and international)
Teacher:
Educational institution: professional lyceum of the metro of St. Petersburg
Academic discipline: chemistry
Subject: "Oxygen-containing and nitrogen-containing organic compounds"
The target audience: 1 course
Lesson type: generalization of material, 1 academic. hour.
Lesson objectives:
Knowledge: know the formulas and properties of oxygen-containing and nitrogen-containing organic substances
Understanding: understand the dependence of the properties of substances on the structure of the molecule, on the functional group
Application: use information about the properties of substances to draw up equations of chemical reactions.
Analysis: analyze the mutual influence of groups of atoms in molecules of organic substances.
Synthesis: summarize information about the properties of organic substances in the form of a chain of transformations
Grade: Conduct self-assessment using the proposed rubrics.
Equipment: interactive whiteboard, multimedia presentation.
Lesson plan:
1. Org. moment
2. Repetition of previously studied.
3. Student performances.
4. Self-determination of students by levels of self-esteem.
5. Independent work of students.
6. Summing up the criteria-oriented system.
7. Homework.
During the classes
1. Organizing time.
Formation of the group, report from the group leader on the number of students present.
2. Repetition of previously learned
Information about functional groups, classes of oxygen-containing and nitrogen-containing substances, about the simplest representatives of these classes using an interactive whiteboard and multimedia presentation.
Which group of atoms, necessarily present in the molecules of substances of this class, determines the chemical function of the substance, i.e., its chemical properties?
Answer: functional group of atoms
Give the name of the functional group - OH
Answer: hydroxyl group of atoms.
What class of substances is determined by the hydroxyl group of atoms?
Answer: Alcohols, if 1 group is OH, monohydric alcohols, if more than one group is OH, polyhydric alcohols.
Give the name of the functional group - SLEEP. What class of substances does it define?
Answer: aldehyde group, defines the class of aldehydes.
Give the name of the functions to the group - SLEEP. What class does it define?
Answer: carboxyl group, defines the class of carboxylic acids.
Give the name of the functions to the group - NH2. What class does it define?
Answer: The amino group defines the class of amines or the class of amino acids.
We listen to student reports with multimedia presentations about the simplest representatives of various classes of oxygen- and nitrogen-containing substances.
3.Student performances.
Message 1.
Ethanol C2H5OH, class monohydric alcohols, functional group - hydroxyl group of atoms - OH. Qualitative reaction - interaction with copper (II) oxide to form an aldehyde. Chemical properties (we distinguish 2 reactions) - combustion and interaction with metals (Na).
Message 2.
Propanetriol (glycerol) C3H7(OH)3. Class – polyhydric alcohols, functional groups – several hydroxyl groups – OH. Qualitative reaction – interaction with copper (II) hydroxide. Chemical properties - interaction with sodium and hydrogen halides.
Laboratory experience:
Pour about 1 ml of copper (II) sumorate solution into a test tube and add a little sodium hydroxide solution until a blue precipitate of copper (II) hydroxide forms. Add glycerin solution drop by drop to the resulting precipitate. Shake the mixture. We note the transformation of the blue precipitate into a blue solution.
(glycerol + Cu(OH)2 ----- blue solution)
Message 3.
Phenol C6H5OH is the simplest representative of the class of phenols.
The functional group is hydroxyl group –OH. Qualitative reaction - the formation of a purple solution when interacting with iron (III) chloride or the formation of a white precipitate when interacting with bromine. Chemical properties: phenol is a weak acid, reacts with metals (Na) with alkalis (NaOH) and bromine.
Message 4.
Ethanol or acetaldehyde CH3-COH Functional group – COH aldehyde group. Class: aldehydes. A qualitative reaction is a “silver mirror” reaction. Chemical properties: reduction reaction and oxidation reaction.
Laboratory experience: demonstration experience.
Add a few drops of an ammonia solution of silver oxide to a test tube containing 1 ml of aldehyde (aqueous solution). We heat the test tube. We observe the release of silver on the walls of the test tube, the surface of the glass becomes mirror-like.
Message 5.
Ethanoic acid CH3-COOH (acetic acid). Class – carboxylic acids. Functional group – COOH carboxyl group. Qualitative reaction - the litmus indicator turns red.
Chemical properties: how any acid interacts with metals (Na), basic oxides (Na2O), alkalis (NaOH).
Laboratory experience:
Pour a little acetic acid into a dry, clean test tube with a universal indicator. The indicator turns red.
Message 6.
Glucose C6H12O6. Class – carbohydrates. Functional groups: 5-OH and 1-COH, i.e. aldehydroalcohol. Qualitative reactions: interaction with copper hydroxide to form a blue solution. The “silver mirror” reaction with the release of silver on the walls of the test tube. Chemical properties: reduction to hexahydric alcohol, oxidation to gluconic acid, fermentation reaction.
Message 7.
Aniline C6H5-NH2.
Functional group – NH2 amino group. Class - amines. Qualitative reaction: interaction with bromine water to form a white precipitate. Chemical properties: interaction with hydrochloric acid and bromine.
Message 8.
Aminoethanoic acid NH2-CH2-COOH or aminoacetic acid.
Class – amino acids. Functional groups: - NH2 amino group and –COOH carboxyl group. Chemical properties: AA – amphoteric compounds; - NH2 imparts basic properties, - COOH imparts acidic properties. Therefore, amino acids are able to combine with each other, forming protein molecules, and protein is the basis of life on our planet.
4. Self-determination of students by levels of self-esteem.
Interactive whiteboard: students get acquainted with the development self-assessment card in class and mark their level.
1. I can identify the functional group and the simplest representative of the class of organic substances with the help of the teacher and notes (6-7 points).
2. I can identify a functional group, the simplest representative of the class of organic substances, without the help of a teacher and without the help of a note (8-10 points).
3. I can determine the qualitative reaction and chemical properties of a substance with the help of a teacher and notes (11-14 points).
4. I can determine the qualitative reaction and chemical properties of a substance without the help of a teacher and without a note (15-18 points).
Class | Functional groups | The simplest representative | Qualitative reactions | Chemical properties |
Monatomic alcohols | ||||
Polyhydric alcohols | ||||
Phenols | ||||
Aldehydes | ||||
Carboxylic acids | ||||
Carbohydrates | ||||
Amines | ||||
Amino acids |
Students become familiar with the criterion-oriented assessment system.
Criteria:
18 – 15 points – “excellent”
points – “good”
10 – 6 points – “satisfactory”
5 or less – “unsatisfactory”
5. Independent work of students.
6. Summing up the results according to the criterion-oriented system (announcing the number of points to students).
7. Homework: filling out the table.
