What is the mechanism of addition reactions to alkenes?
1. Due to the electrons of the π bond, alkene molecules have a region of increased electron density (a cloud of π electrons above and below the plane of the molecule):
Therefore, the double bond is prone to be attacked by an electrophilic (electron-deficient) reagent. In this case, heterolytic cleavage of the π bond will occur and the reaction will proceed along ionic mechanism as electrophilic addition.
2. On the other hand, the carbon-carbon π bond, being non-polar, can be broken homolytically, and then the reaction will proceed along radical mechanism.
The mechanism of addition depends on the reaction conditions.
In addition, alkenes are characterized by reactions isomerizationAndoxidation (including reaction combustion, characteristic of all hydrocarbons).
Addition reactions to alkenes.
Hydrogenation (addition of hydrogen)
Alkenes react with hydrogen when heated and under elevated pressure in the presence of catalysts (Pt, Pd, Ni, etc.) to form alkanes:
Hydrogenation of alkenes is the reverse reaction to the dehydrogenation of alkanes. According to Le Chatelier's principle, hydrogenation is favored by increased pressure because this reaction is accompanied by a decrease in the volume of the system.
The addition of hydrogen to carbon atoms in alkenes leads to a decrease in their oxidation state:
Therefore, the hydrogenation of alkenes is classified as a reduction reaction. This reaction is used industrially to produce high-octane fuel.
Halogenation (addition of halogens)
Addition of halogens double bond C=C occurs easily in normal conditions(at room temperature, without catalyst). For example, the rapid discoloration of the red-brown color of a solution of bromine in water (bromine water) serves qualitative reaction for the presence of a double bond:
The addition of chlorine occurs even more easily:
These reactions proceed by the mechanism of electrophilic addition with heterolytic cleavage of bonds in the halogen molecule.
When heated to 500 °C, radical substitution of the hydrogen atom at the carbon atom adjacent to the double bond is possible:
Hydrohalogenation (addition of hydrogen halides)
The reaction proceeds by the mechanism of electrophilic addition with heterolytic bond cleavage.
CH 2 =CH 2 + HCl CH 3 -CH 2 Cl
The direction of the reaction of addition of hydrogen halides to alkenes of asymmetrical structure (for example, to propylene CH 2
=CH–CH 3
) is determined by Markovnikov’s rule:
In addition reactions of polar molecules such as HX to unsymmetrical alkenes, hydrogen attaches to the more hydrogenated carbon atom at the double bond (i.e., the carbon atom bonded to the largest number of hydrogen atoms).
So, in HCl reactions with propylene from two possible structural isomers 1-chloropropane and 2-chloropropane, the latter is formed:
It should be noted that Markovnikov's rule in its classical formulation is observed only for electrophilic reactions of alkenes themselves. In the case of some derivatives of alkenes or when the reaction mechanism changes, they go against Markovnikov's rule.
Hydration(water connection)
Hydration occurs in the presence mineral acids by the mechanism of electrophilic addition:
In reactions of unsymmetrical alkenes, Markovnikov's rule is observed.
Polymerization– the reaction of the formation of a high molecular weight compound (polymer) by sequential addition of molecules of a low molecular weight substance (monomer) according to the scheme:
nM M n
Number n in the polymer formula ( M n) is called the degree of polymerization. Polymerization reactions of alkenes occur due to addition via multiple bonds:
Preparation of alkenes
In nature, alkenes occur to a much lesser extent than saturated hydrocarbons, apparently due to their high reactivity. Therefore, they are prepared using various reactions.
I. Cracking of alkanes:
For example:
II. The detachment (elimination) of two atoms or groups of atoms from neighboring carbon atoms with the formation of an bond between them.
Dehydrohalogenation of haloalkanes under the action of an alcoholic alkali solution
Dehydration of alcohols at elevated temperatures (above 140 C) in the presence of water-removing reagents
Elimination reactions proceed in accordance with ruleZaitseva:
The abstraction of a hydrogen atom in dehydrohalogenation and dehydration reactions occurs predominantly from the least hydrogenated carbon atom.
Modern formulation: elimination reactions proceed with the formation of alkenes that are more substituted at the double bond.
Such alkenes have lower energy.
Dehalogenation of dihaloalkanes having halogen atoms at neighboring carbon atoms under the action of active metals:
Dehydrogenation of alkanes at 500С:
Applications of alkenes
Alkenes are used as starting products in the production of polymeric materials (plastics, rubbers, films) and other organic substances.
Ethylene(ethene) H 2 C=CH 2 is used to produce polyethylene, polytetrafluoroethylene (Teflon), ethyl alcohol, acetaldehyde, halogen derivatives and many others organic compounds.
It is used as a means to accelerate the ripening of fruits.
Propylene(propene) H 2 C=CH 2 –CH 3 and butylenes(butene-1 and butene-2) are used to produce alcohols and polymers.
Isobutylene(2-methylpropene) H 2 C=C(CH 3) 2 is used in the production of synthetic rubber.
What hydrocarbons are called alkenes?
What is general formula alkenes?
What type of hybridization do alkenes have?
What chemical properties are characteristic of alkenes?
Why are alkenes used as a starting product for the production of IUDs?
What is the essence of Markovnikov's rule?
What methods of producing alkenes do you know?
By what mechanism does the addition reaction occur in alkenes?
How do they change? physical properties V homologous series in alkenes?
Where are alkenes used?
Lecture No. 17: Alkadienes. Structure. Properties. Rubber.
Alkadienes (dienes)– unsaturated aliphatic hydrocarbons, the molecules of which contain two double bonds.
General formula of alkadienes WITH n H 2n-2 .
The properties of alkadienes largely depend on the relative arrangement of double bonds in their molecules. Based on this feature, three types of double bonds in dienes are distinguished.
1. Isolated double bonds are separated in the chain by two or more σ bonds:
CH 2 =CH–CH 2 –CH=CH 2
Separated by sp 3 -carbon atoms, such double bonds do not mutually influence each other and enter into the same reactions as the double bond in alkenes. Thus, alkadienes of this type exhibit chemical properties characteristic of alkenes.
2. Cumulated double bonds are located at one carbon atom:
CH 2 =C=CH 2 (allen)
Such dienes (allenes) belong to a rather rare type of compounds.
3. Conjugated double bonds are separated by one σ bond:
CH 2 =CH–CH=CH 2
Conjugated dienes are of greatest interest. They are distinguished by characteristic properties due to the electronic structure of the molecules, namely, a continuous sequence of 4 sp 2 carbon atoms.
Some representatives of these dienes are widely used in the production of synthetic rubbers and various organic substances.
According to IUPAC rules, the backbone of an alkadiene molecule must include both double bonds. The carbon atoms in the chain are numbered so that the double bonds receive the lowest numbers. The names of alkadienes are derived from the names of the corresponding alkanes (with the same number of carbon atoms), in which last letter replaced by ending –diene.
The location of double bonds is indicated at the end of the name, and the location of substituents is indicated at the beginning of the name.
For example:
The name "divinyl" comes from the name of the radical –CH=CH 2 "vinyl".
Isomerism of conjugated dienes
Structural isomerism
1. Isomerism of the position of conjugated double bonds:
2. Isomerism of the carbon skeleton:
3. Interclass isomerism with alkynes and cycloalkenes.
For example, the formula WITH 4 N 6 The following connections correspond:
Spatial isomerism
Dienes, which have different substituents on the carbon atoms of their double bonds, like alkenes, exhibit cis-trans isomerism.
In addition, rotation at the σ bond separating double bonds is possible, leading to rotary isomers. Some chemical reactions of conjugated dienes proceed selectively only with a certain rotary isomer.
Properties of conjugated alkadienes
Of greatest practical importance are divinyl or butadiene-1,3 (easily liquefied gas, bp = – 4.5 °C) and isoprene or 2-methylbutadiene-1,3 (liquid with bp = 34 °C).
The chemical properties of diene hydrocarbons are similar to alkenes. They are easily oxidized and undergo addition reactions. However, conjugated dienes differ in some features, which are due to the delocalization (dispersal) of π electrons.
Butadiene-1,3 molecule CH 2 =CH-CH=CH 2 contains four carbon atoms in the sp 2 -hybridized state and has a flat structure.
The π-electrons of double bonds form a single π-electron cloud (conjugated system) and are delocalized between all carbon atoms.
The bond order (number of shared electron pairs) between carbon atoms is intermediate between 1 and 2, i.e. There are no purely single or purely double bonds. The structure of butadiene is more accurately reflected by the formula with delocalized bonds.
Isoprene molecules are constructed similarly:
Formation of a single π-electron cloud covering 4 carbon atoms:
leads to the possibility of attaching a reagent to the ends of this system, i.e. to the C 1 and C 4 atoms. Therefore, divinyl and isoprene, along with the addition of 1 mole of the reagent at one of the double bonds (1,2- or 3,4-), enter into 1,4-addition reactions. The ratio of 1,2- and 1,4-addition products depends on the reaction conditions (with increasing temperature, the probability of 1,4-addition usually increases).
Polymerization of conjugated dienes. Rubbers
Divinyl and isoprene undergo polymerization and copolymerization (i.e., co-polymerization) with other unsaturated compounds, forming rubbers. Rubbers are elastic high-molecular materials (elastomers), from which rubber is produced by vulcanization (heating with sulfur).
Natural rubber– natural high-molecular unsaturated hydrocarbon of composition (C 5 H 8) n, where n is 1000-3000 units. It has been established that this polymer consists of repeating 1,4-cis-isoprene units and has a stereoregular structure:
Under natural conditions, natural rubber is not formed by polymerization of isoprene, but by another, more complex method.
Polymerization of 1,3-dienes can proceed either by the 1,4-addition type or by a mixed type of 1,2- and 1,4-addition. The direction of addition depends on the reaction conditions.
The first synthetic rubber obtained using the method of S.V. Lebedev during the polymerization of divinyl under the influence of metallic sodium, was a polymer of irregular structure with mixed type links 1,2- and 1,4-connection:
In the presence of organic peroxides (radical polymerization), a polymer of irregular structure with 1,2- and 1,4-addition units is also formed. Rubbers of irregular structure are characterized by low quality during operation. Selective 1,4-addition occurs when using organometallic catalysts (for example, butyllithium C 4 H 9 Li, which not only initiates polymerization, but also coordinates the joining diene molecules in space in a certain way):
In this way, stereoregular 1,4-cis-polyisoprene was obtained – synthetic analogue natural rubber. This process proceeds as ionic polymerization.
For practical use, rubbers are converted into rubber. Rubber - it is vulcanized rubber with filler (carbon black). The essence of the vulcanization process is that heating a mixture of rubber and sulfur leads to the formation of a three-dimensional network structure of linear rubber macromolecules, giving it increased strength. Sulfur atoms attach to the double bonds of macromolecules and form cross-linking disulfide bridges between them:
The network polymer is more durable and exhibits increased elasticity - high elasticity (the ability to undergo high reversible deformations).
Depending on the amount of crosslinking agent (sulfur), meshes with different crosslinking frequencies can be obtained. Extremely cross-linked natural rubber - ebonite - does not have elasticity and is a hard material.
Preparation of alkadienes
General methods for preparing dienes are similar to methods for producing alkenes.
1. Catalytic two-stage dehydrogenation of alkanes (through the stage of formation of alkenes). In this way, divinyl is produced industrially from butane contained in oil refining gases and associated gases:
Isoprene is obtained by catalytic dehydrogenation of isopentane (2-methylbutane):
2. Synthesis of divinyl according to Lebedev:
3. Dehydration of glycols ( dihydric alcohols, or alkanediols):
4. The effect of an alcohol solution of alkali on dihaloalkanes (dehydrohalogenation):
Questions to reinforce the topic:
What hydrocarbons are called diene hydrocarbons?
What types of isomerism are observed in alkadienes?
What chemical properties are characteristic of diene hydrocarbons?
How can alkadienes be prepared?
What type of hybridization is typical for alkadienes?
What is rubber?
What is rubber?
What determine the physical properties of alkadienes?
What substances are the chemical properties of alkadienes similar to?
Lecture No. 18: Alkynes. Structure, properties, application.
Alkynes (acetylene hydrocarbons)– unsaturated aliphatic hydrocarbons, the molecules of which contain a triple bond C≡C.
General formula of alkynes with one triple bond WITH n H 2n-2 .
The triple bond C≡C is carried out by 6 shared electrons:
The formation of such a bond involves carbon atoms in sp-hybridized state. Each of them has two sp-hybrid orbitals directed to each other at an angle of 180, and two non-hybrid R-orbitals located at an angle of 90 relative to each other and to sp-hybrid orbitals:
Structure of the triple bond C≡C
A triple bond is a combination of one σ and two π bonds formed by two sp-hybridized atoms. σ-bond occurs when there is axial overlap sp-hybrid orbitals of neighboring carbon atoms; one of the π bonds is formed by lateral overlap R y-orbitals, the other – with lateral overlap R z-orbitals. The formation of bonds using the example of an acetylene molecule H–C≡C–H can be depicted in the form of a diagram:
C≡C σ-bond (overlap 2 sp-2sp);
π bond (2 R y -2 R y);
π bond (2 R z -2 R z);
C–H σ bond (overlap 2 sp-AO carbon and 1 s-AO hydrogen).
π-Bonds are located in mutually perpendicular planes:
σ-Bonds formed sp– hybrid carbon orbitals, located on the same straight line (at an angle of 180 to each other). Therefore, the acetylene molecule has a linear structure:
Alkyne nomenclature
According to systematic nomenclature, the names of acetylene hydrocarbons are derived from the names of the corresponding alkanes (with the same number of carbon atoms) by replacing the suffix –an on –in :
2 atoms C → ethane → eth in ; 3 atoms C → propane → prop in etc.
The main chain is selected in such a way that it necessarily includes a triple bond (i.e. it may not be the longest).
The numbering of carbon atoms begins with the end of the chain closest to the triple bond. The number indicating the position of the triple bond is usually placed after the suffix –in . For example:
For the simplest alkenes, historical names are also used: acetylene(ethin), allylene(propyne), crotonylene(butine-1), valerylene(pentin-1).
In the nomenclature of various classes of organic compounds, the following monovalent alkyne radicals are most often used:
Alkyne isomerism
Structural isomerism
Isomerism of the position of the triple bond (starting from C 4 H 6):
Isomerism of the carbon skeleton (starting from C 5 H 8):
Interclass isomerism with alkadienes and cycloalkenes, starting with C 4 H 6:
Spatial isomerism with respect to the triple bond does not appear in alkynes, because Substituents can only be positioned in one way—along the bond line.
Properties of alkynes
Physical properties. The boiling and melting points of acetylene hydrocarbons increase with increasing molecular weight. Under normal conditions, alkynes C 2 H 2 -C 4 H 6 are gases, C 5 H 8 -C 16 H 30 are liquids, and C 17 H 32 are solids. The boiling and melting points of alkynes are higher than those of the corresponding alkenes.
Physical properties of alkynes and alkenes
Alkynes are poorly soluble in water, but better in organic solvents.
Chemical properties.
Addition reactions to alkynes
1. Hydrogenation
In the presence of metal catalysts (Pt, Ni), alkynes add hydrogen to form alkenes (the first π bond is broken), and then alkanes (the second π bond is broken):
When using a less active catalyst, hydrogenation stops at the stage of formation of alkenes.
2. Halogenation
The electrophilic addition of halogens to alkynes proceeds more slowly than for alkenes (the first π bond is more difficult to break than the second):
Alkynes discolor bromine water(qualitative reaction).
Explanatory note (6)
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Addition reactions.
1.1. Accession
CH 2 = CH 2 + H 2 ® CH 3 -CH 3
The reaction occurs in the presence of catalysts (Pd, Pt, Ni).
1.2. Halogen addition:
CH 2 = CH 2 + Br 2 ® CH 2 Br-CH 2 Br
1.3. Addition of hydrogen halides:
CH 2 = CH 2 + HC1 ® CH 3 -CH 2 C1
The addition of hydrogen halides to ethylene homologues occurs according to V.V. Markovnikov’s rule: the hydrogen atom becomes the most hydrogenated carbon atom, and the halogen atom becomes the least hydrogenated, for example:
CH 3 -CH = CH 2 + HBr->CH 3 - CH Br –CHz
1.4. Addition of water (hydration reaction). The reaction takes place in the presence of a catalyst - sulfuric acid:
CH 2 = CH 2 + H 2 O ® CH 3 - CH 2 OH
This is the overall reaction equation. In reality, the reaction occurs in two stages. First, sulfuric acid combines with ethylene at the site where the double bond is broken to form ethyl sulfuric acid:
CH 2 = CH 2 + H- O- SO 2 - OH ® CH3- CH 2 - O- SO 2 -OH
Then ethyl sulfuric acid, interacting with water, forms alcohol and acid:
CH 3 - CH 2 - O-SO 2 - OH + H - OH ® CH 3 - CH 2 OH + HO- SO 2 - OH
Currently, the reaction of adding water to ethylene in the presence of solid catalysts is used for industrial production ethyl alcohol from unsaturated hydrocarbons contained in petroleum cracking gases (associated gases), as well as in coke oven gases.
2. Important chemical property ethylene and its homologues is the ability to easily oxidize even at ordinary temperatures. In this case, both carbon atoms connected by a double bond undergo oxidation. If ethylene is passed into water solution potassium permanganate KMpO 4, then characteristic purple color the latter disappears - ethylene is oxidized with potassium permanganate:
ZSN 2 = CH 2 + 2KMp0 4 + 4H 2 O ® ZNON 2 C - CH 2 OH + 2MnO 2 + 2KOH
ethylene glycol
This reaction is used to determine the unsaturation of an organic substance - the presence of double or triple bonds in it.
2.2. Ethylene burns with a luminous flame to produce carbon monoxide (IV) and water:
CH 2 = CH 2 + 4 O 2 ® 2CO 2 + 4H 2 O
3. Polymerization reactions.
Polymerization is serial connection identical molecules into larger ones.
Polymerization reactions are especially characteristic of unsaturated compounds. So, for example, a high-molecular substance - polyethylene - is formed from ethylene. Compound of ethylene molecules
occurs at the site where the double bond is broken. Abbreviated equation this reaction is written as follows: nCH 2 = CH 2 ® (- CH 2 - CH 2 - ) n
Some free atoms or radicals (for example, hydrogen atoms from ethylene) are attached to the ends of such molecules (macromolecules). The product of the polymerization reaction is called a polymer (from the Greek poly - many, meros - part), and the starting substance entering the polymerization reaction is called a monomer.
Polymer is a substance with a very large relative molecular weight, the molecule of which consists of large number repeating groups that have the same structure. These groups are called elementary units or structural units. For example, the elementary unit of polyethylene is the group of atoms - CH 2 - CH 2 -.
The number of elementary units repeated in a macromolecule is called the degree of polymerization (denoted n). Depending on the degree of polymerization, substances with different properties can be obtained from the same monomers.
Thus, polyethylene with short chains (n=20) is a liquid with lubricating properties. Polyethylene with a chain length of 1500 - 2000 links is a hard but flexible plastic material from which films can be made, bottles and other dishes, elastic pipes, etc. Finally, polyethylene with a chain length of 5 - 6 thousand links is solid, from which you can prepare cast products, rigid pipes, and strong threads.
If a small number of molecules take part in the polymerization reaction, then low molecular weight substances are formed, for example dimers, trimers, etc. The conditions for polymerization reactions are very different. Sometimes catalysts and high pressure are needed. But the main factor is the structure of the monomer molecule. Unsaturated (unsaturated) compounds enter into the polymerization reaction due to the breaking of multiple bonds.
The structural formulas of polymers are briefly written as follows: the formula of the elementary unit is enclosed in brackets and the letter p is placed at the bottom right. For example, structural formula polyethylene (- CH 2 - CH 2 - ) P. It is easy to conclude that the name of the polymer is made up of the name of the monomer and the prefix poly-, for example polyethylene, polyvinyl chloride, polystyrene, etc.
Using polymerization reactions, high molecular weight synthetic substances are obtained, for example polyethylene, polytetrafluoroethylene (Teflon), polystyrene, synthetic rubbers etc. They are of great economic importance.
Teflon is a product of the polymerization of tetrafluoroethylene:
nCF 2 = CF 2 ->-(-CF 2 - CF 2 -)
This is the most inert organic substance (it is affected only by molten potassium and sodium). Has high frost and heat resistance.
Application. Ethylene is used to produce ethyl alcohol and polyethylene. It accelerates the ripening of fruits (tomatoes, citrus fruits, etc.) when small quantities are introduced into the air of greenhouses. Ethylene and its homologues are used as chemical raw materials for the synthesis of many organic substances.
- it's not only chemical element, but also a simple substance that is part of a wide variety of compounds. Hydrogen compounds are complex substances, which contain hydrogen atoms. The variety of such compounds is very large. They can be either natural, natural, or artificially obtained by man. In both cases, hydrogen compounds are of enormous importance.
Hydrogen compounds
Hydrogen combines with chlorine at high speed under the influence of light; oxygen and hydrogen (this compound is called detonating gas) does not react at all at ordinary temperatures, but under the influence of a spark or local heating it explodes with great strength. When it burns a gram molecule (2.02 g) of hydrogen, 68.4 large calories are released. At elevated temperatures, hydrogen combines with a number of elements, for example, with sulfur, phosphorus, bromine, alkali and alkaline earth metals, and at sufficiently high temperature forms the corresponding hydrogen compounds with carbon.
Oxides of copper, lead, iron, nickel and some other metals are reduced into the corresponding metals when heated in a hydrogen stream. The activity of hydrogen increases enormously in the presence of certain catalysts, as well as with increasing pressure. At ordinary temperatures, such catalysts are especially finely divided metals - palladium, platinum and nickel.
In the presence of these catalysts, hydrogen readily attaches to unsaturated organic compounds; this is precisely what is based on a large number of processes that have a large technical significance, such as, for example, the production of solid fats from liquid fats containing unsaturated fatty acids, which, by adding hydrogen in the presence of nickel, become saturated.
The reaction of combining hydrogen with oxygen is so accelerated by platinum that spongy platinum, saturated with hydrogen, spontaneously heats up in air (hydrogen flint). It is very likely that the action of these catalysts is based on their ability to dissolve hydrogen, and in this case the hydrogen passes into the atomic state. The amount of hydrogen absorbed by the metal is especially significant in the case of palladium.
A whole range of others most important reactions, in which hydrogen is added: ammonia synthesis according to Haber, obtaining methyl alcohol from carbon monoxide, obtaining synthetic oil according to Fischer, also occurs only in the presence of appropriate catalysts, and their implementation became possible only when these catalysts were found and the conditions for their action were determined.
Applications of hydrogen
High pressure also greatly increases the activity of hydrogen: thus, at high pressure, hydrogen displaces copper and other metals from solutions of their salts; on application high pressures The Bergius method is also based, in which coal under the influence of hydrogen is converted into a mixture of liquid hydrocarbons. Among the above catalytic processes, the reactions for the formation of ammonia and methyl alcohol also require the use of high pressures.
The technical uses of hydrogen are based partly on its low specific gravity(for example, filling balloons), partly at high temperatures resulting from the combustion of hydrogen (for example, the use of hydrogen in soldering lead and in autogenous welding of metals). Next come numerous hydrogenation and reduction reactions, primarily the hydrogenation of liquid fats and the production of synthetic methyl alcohol.
Among other reactions of this kind, the hydrogenation of naphthalene and the production of ethyl alcohol from acetaldehyde are also very important. However, greatest number hydrogen is currently consumed by plants producing synthetic ammonia according to Haber; Huge quantities of hydrogen will also be required for the production of synthetic liquid fuel when the methods of Bergius and Fischer are technically implemented.
Hydrogen in the periodic table is located at number one, in I and VII groups straightaway. The symbol for hydrogen is H (lat. Hydrogenium). It is a very light gas, colorless and odorless. There are three isotopes of hydrogen: 1H - protium, 2H - deuterium and 3H - tritium (radioactive). Air or oxygen in reaction with simple hydrogen H₂ is highly flammable and also explosive. Hydrogen does not emit toxic products. It is soluble in ethanol and a number of metals (especially the side subgroup).
Hydrogen abundance on Earth
Like oxygen, hydrogen has great value. But, unlike oxygen, almost all hydrogen is bound to other substances. It is found in a free state only in the atmosphere, but its quantity there is extremely insignificant. Hydrogen is part of almost all organic compounds and living organisms. Most often it is found in the form of an oxide - water.
Physicochemical characteristics
Hydrogen is inactive, and when heated or in the presence of catalysts, it reacts with almost all simple and complex chemical elements.
Reaction of hydrogen with simple chemical elements
At elevated temperatures, hydrogen reacts with oxygen, sulfur, chlorine and nitrogen. you will learn what experiments with gases can be done at home.
Experience of interaction of hydrogen with oxygen in laboratory conditions
Let's take pure hydrogen, which comes through the gas outlet tube, and set it on fire. It will burn with a barely noticeable flame. If you place a hydrogen tube in any vessel, it will continue to burn, and water droplets will form on the walls. This oxygen reacted with hydrogen:
2Н₂ + О₂ = 2Н₂О + Q
When hydrogen burns, a lot of thermal energy is generated. The temperature of the combination of oxygen and hydrogen reaches 2000 °C. Oxygen oxidized hydrogen, so this reaction is called an oxidation reaction.
Under normal conditions (without heating), the reaction proceeds slowly. And at temperatures above 550 ° C an explosion occurs (the so-called detonating gas is formed). Previously, hydrogen was often used in balloons, but due to the formation of detonating gas there were many disasters. The integrity of the ball was violated, and an explosion occurred: hydrogen reacted with oxygen. Therefore, helium is now used, which is periodically heated with a flame.
Chlorine reacts with hydrogen to form hydrogen chloride (only in the presence of light and heat). Chemical reaction hydrogen and chlorine looks like this:
H₂ + Cl₂ = 2HCl
Interesting fact: the reaction of fluorine with hydrogen causes an explosion even in darkness and temperatures below 0 ° C.
The interaction of nitrogen with hydrogen can only occur when heated and in the presence of a catalyst. This reaction produces ammonia. Reaction equation:
ЗН₂ + N₂ = 2NN₃
The reaction of sulfur and hydrogen occurs to form a gas - hydrogen sulfide. The result is a rotten egg smell:
H₂ + S = H₂S
Hydrogen not only dissolves in metals, but can also react with them. As a result, compounds are formed that are called hydrides. Some hydrides are used as fuel in rockets. They are also used to produce nuclear energy.
Reaction with complex chemical elements
For example, hydrogen with copper oxide. Let's take a tube of hydrogen and pass it through the copper oxide powder. The entire reaction occurs when heated. Black copper powder will turn brownish red (plain copper color). Droplets of liquid will also appear on the unheated areas of the flask - this has formed.
Chemical reaction:
CuO + H₂ = Cu + H₂O
As we can see, hydrogen reacted with the oxide and reduced copper.
Recovery reactions
If a substance removes an oxide during a reaction, it is a reducing agent. Using the example of the reaction of copper oxide with we see that hydrogen was a reducing agent. It also reacts with some other oxides such as HgO, MoO₃ and PbO. In any reaction, if one of the elements is an oxidizing agent, the other will be a reducing agent.
All hydrogen compounds
Hydrogen compounds with nonmetals- very volatile and poisonous gases(eg hydrogen sulfide, silane, methane).
Hydrogen halides- Hydrogen chloride is most commonly used. When dissolved it forms hydrochloric acid. This group also includes: hydrogen fluoride, hydrogen iodide and hydrogen bromide. All these compounds result in the formation of the corresponding acids.
Hydrogen peroxide (chemical formulaН₂О₂) exhibits strong oxidizing properties.
Hydrogen hydroxides or water H₂O.
Hydrides- these are compounds with metals.
Hydroxides- these are acids, bases and other compounds that contain hydrogen.
Organic compounds: proteins, fats, lipids, hormones and others.