Strong oxidizing agents. Typical reducing and oxidizing agents. Topic: Redox reactions

Before identifying the strongest oxidizing agents, we will try to clarify the theoretical issues related to this topic.

Definition

In chemistry, an oxidizing agent refers to neutral atoms or charged particles that accept electrons from other particles in interactions.

Examples of oxidizing agents

In order to determine the strongest oxidizing agents, it should be noted that this indicator depends on the degree of oxidation. For example, in potassium permanganate for manganese it is +7, that is, it is maximum.

This compound, better known as potassium permanganate, exhibits typical oxidizing properties. It can be used in organic chemistry for qualitative reactions for multiple connections.

When determining the strongest oxidizing agents, we will focus on nitric acid. It is rightly called the queen of acids, because this particular compound, even in diluted form, is capable of interacting with metals located in the electrochemical series of metal voltages after hydrogen.

When considering the most powerful oxidizing agents, chromium compounds cannot be ignored. Chromium salts are considered one of the brightest oxidizing agents; they are used in qualitative analysis.

Oxidizing agents groups

Both neutral molecules and charged particles (ions) can be considered as oxidizing agents. If you analyze atoms of chemical elements that exhibit similar properties, then it is necessary that they contain from four to seven electrons.

It is understood that it is p-elements that exhibit strong oxidizing characteristics, and these include typical non-metals.

The most powerful oxidizing agent is fluorine, a representative of the halogen subgroup.

Among the weak oxidizing agents, we can consider representatives of the fourth group of the periodic table. There is a natural decrease in the oxidizing properties in the main subgroups with increasing atomic radius.

Taking into account this pattern, it can be noted that lead exhibits minimal oxidizing properties.

The strongest non-metal oxidizing agent is one that is not capable of donating electrons to other atoms.

Elements such as chromium and manganese, depending on the environment in which the chemical interaction takes place, can exhibit not only oxidizing, but also reducing properties.

They can change their oxidation state from a lower value to a higher one, giving electrons to other atoms (ions) for this purpose.

Ions of all noble metals, even in a minimal degree of oxidation, exhibit strong oxidizing properties, actively entering into chemical interactions.

When talking about strong oxidizing agents, it would be wrong to ignore molecular oxygen. It is this diatomic molecule that is considered one of the most accessible and widespread types of oxidizing agents, and therefore is widely used in organic synthesis. For example, in the presence of an oxidizing agent in the form of molecular oxygen, ethanol can be converted into ethanal, which is necessary for the subsequent synthesis of acetic acid. By oxidation it can be obtained from natural gas even organic alcohol (methanol).

Conclusion

Redox processes are important not only for carrying out some transformations in a chemical laboratory, but also for the industrial production of various organic and inorganic products. That is why it is so important to choose the right oxidizing agents in order to increase the efficiency of the reaction and increase the yield of the reaction product.

According to their function in redox processes, their participants are divided into oxidizing agents and reducing agents.

Oxidizing agents are atoms, molecules or ions that accept electrons from other atoms. The oxidation state of the oxidizing agent decreases.

Restorers– atoms, molecules or ions that donate electrons to other atoms. The oxidation state of the reducing agent increases. During redox reaction, the oxidizing agent is reduced, the reducing agent is oxidized, and both processes occur simultaneously.

Accordingly, oxidizing agents and reducing agents interact in such proportions that the numbers of electrons accepted and given up are the same.

The specific manifestation of oxidizing or reducing properties by atoms of various elements depends on many factors. The most important of them include the position of the element in the periodic table, the oxidation state of the element in a given substance, the special properties of other participants in the reaction (the nature of the medium for solutions, the concentration of reagents, temperature, stereochemical properties of complex particles, etc.)

Oxidizing agents.

Oxidizing agents can be both simple and complex substances. Let's try to determine what factors determine the oxidative (and reductive) properties of substances.

The oxidizing ability of simple substances can be judged by the values ​​of relative electronegativity ( χ ). This concept reflects the ability of an atom to shift electron density towards itself from other atoms, i.e. is actually a measure of oxidizing capacity simple substances. Indeed, the strongest oxidizing properties are exhibited by active nonmetals with maximum electronegativity values. So, fluorineF 2 exhibits only oxidizing properties, since it has the most great importanceχ , equal to 4.1 (on the Allred-Rochow scale). The second place is occupied by oxygen O 2, for it χ = 3.5, ozone O 3 exhibits even stronger oxidizing properties. The third place is taken by nitrogen ( χ =3.07), but its oxidizing properties appear only at high temperatures, since the nitrogen molecule N 2 has very high strength, because atoms are connected by a triple bond. Chlorine and bromine have fairly strong oxidizing properties.

On the other hand, the minimum values ​​of electronegativity are inherent in metals ( χ = 0.8-1.6). This means that the intrinsic electrons of metal atoms are held very loosely and can easily move to atoms with higher electronegativity. Metal atoms to the zero degree can exhibit only restorative properties and cannot accept electrons. The most pronounced reducing properties are exhibited by metals of groups IA and IIA.

Redox properties of complex substances

The criterion for the oxidizing ability of atoms can be the degree of oxidation. The maximum oxidation state corresponds to the transfer of all valence electrons to other atoms. Such an atom can no longer give away electrons, but can only accept them. Thus, in maximum oxidation state, an element can exhibit only oxidizing properties A. However, it should be noted that the maximum degree of oxidation does not automatically mean the manifestation of pronounced oxidizing properties. In order for the properties of a strong oxidizing agent to be realized, the particle must be unstable, maximally asymmetrical, with an uneven distribution of electron density. Thus, in dilute solutions the sulfate ion SO 4 2- containing a sulfur atom in the maximum oxidation state +6 , does not exhibit oxidizing properties at all, since it has a highly symmetric tetrahedral structure. Whereas in concentrated solutions of sulfuric acid, a significant proportion of particles are in the form of undissociated molecules and HSO 4 - ions, which have an asymmetric structure with an uneven distribution of electron density. As a consequence of this, concentrated sulfuric acid, especially when heated, is a very strong oxidizing agent.

On the other hand, the minimum oxidation state of an element means that the nonmetal atom has accepted the maximum possible number of electrons into valence sublevels and can no longer accept electrons. Hence,

non-metal atoms in the minimum oxidation state can exhibit only reducing properties.

It may be recalled that the minimum oxidation state of a non-metal is equal to the group number –8. As in the case of sulfuric acid, to realize the reducing properties it is not enough to have only a minimal oxidation state. An example is nitrogen in the –3 oxidation state. The highly symmetrical ammonium ion NH 4 + is an extremely weak reducing agent in solution. The ammonia molecule, which has less symmetry, exhibits fairly strong reducing properties when heated. The reduction reaction from oxides can be given:

3FeO+ 2NH 3 = 3Fe+3H 2 O+N 2.

As for simple substances with intermediate values ​​of electronegativity ( χ = 1.9 – 2.6), then for non-metals one can expect the implementation of both oxidizing and reducing properties. Such substances include hydrogenH2, carbonC, phosphorusP, sulfurS, iodineI2 and other non-metals of average activity. Naturally, metals simple substances are excluded from this category because cannot accept electrons.

These substances, when interacting with active oxidizing agents, exhibit the properties of reducing agents, and when reacting with reducing agents, they exhibit the properties of oxidizing agents. As an example, we give the reactions of sulfur:

0 0 +4 -2 0 0 +2 -2

S+O 2 =SO 2 Fe+S=FeS

As you can see, in the first reaction sulfur is a reducing agent, and in the second it is an oxidizing agent.

Complex substances containing atoms in intermediate oxidation states will also exhibit the properties of both oxidizing and reducing agents. There are a lot of such substances, so we will name only the most common ones. These are sulfur compounds (+4): in an acidic environment SO 2, and in an alkaline and neutral environment SO 3 2- and HSO 3 -. If these compounds participate in the reaction as reducing agents, then they will be oxidized to sulfur +6 (in the gas phase to SO 3, and in solution to SO 4 2-. If sulfur compounds (+4) react with active reducing agents, then reduction occurs to elemental sulfur, or even hydrogen sulfide.

SO 2 + 4HI=S+ 2I 2 +2H 2 O

Many nitrogen compounds also exhibit redox duality. The behavior of NO 2 nitrite ions is of particular interest - . When they are oxidized, nitrate ion NO 3 is formed - , and upon reduction gaseous nitrogen monoxide NO. Example: 2NaNO 2 + 2NaI+2H 2 SO 4 =I 2 +NO+ 2Na 2 SO 4 +2H 2 O.

Let's look at another example, this time taking hydrogen peroxide, in which the oxidation state of oxygen is (-1). If oxidation of this substance takes place, the degree of oxygen will increase to 0, and the release of hydrogen gas will be observed:

H 2 O 2 +Cl 2 = 2HCl+O 2.

In oxidation reactions, the oxidation state of oxygen in peroxides is reduced to (-2), which corresponds to either water H 2 O or hydroxide ion OH - . As an example, we give a reaction often used in restoration work, in which black lead sulfide, under the action of a dilute solution of hydrogen peroxide, is converted into white sulfate: PbS (black) + 4H 2 O 2 = PbSO 4 (white) + 4H 2 O.

Thus, to complete the introductory part, we present the main oxidizing agents, reducing agents and substances that can exhibit both oxidizing and reducing properties.

Oxidizing agents:F 2 , O 2 , O 3 , Cl 2 , Br 2 , HNO 3 , H 2 SO 4 (conc.), KMnO 4 , K 2 Cr 2 O 7 , PbO 2 , NaBiO 3 , Fe 3+ ions in aqueous solution ,Cu 2+ ,Ag + .

Restorers:H 2 S, (S 2-), HI (I -), HBr (Br -), HCl (weak), NH 3 (at high temperatures), ions in aqueous solution Fe 2+, Cr 2+, Sn 2+ and etc.

Substances with dual properties:H 2 ,C,P,As,S,I 2 ,CO,H 2 O 2 ,Na 2 O 2 ,NaNO 2 ,SO 2 (SO 3 2-) and, formally, almost all substances containing atoms with intermediate degree of oxidation.

Drawing up equations for redox reactions.

There are several ways to compose OVR equations. Typically used

a) electronic balance method,

b) electron-ion balance method.

Both methods are based on finding such quantitative relationships between the oxidizing agent and the reducing agent, at which equality of received and given electrons is observed.

The electronic balance method is more universal, although less visual. It is based on calculating the change in the oxidation states of the oxidizing and reducing atoms in the initial and final substances. When working with this method, it is convenient to follow this algorithm.

The molecular diagram of the redox reaction is written down,

The oxidation states of atoms (usually those that change it) are calculated

The oxidizing agent and the reducing agent are determined,

The number of electrons accepted by the oxidizing agent and the number of electrons given up by the reducing agent are established,

The coefficients are found, when multiplied by which the numbers of given and received electrons are equalized,

Coefficients are selected for other participants in the reaction.

Let's consider the oxidation reaction of hydrogen sulfide.

H 2 S + O 2 = SO 2 + H 2 O

In this reaction, sulfur (-2) is the reducing agent and molecular oxygen is the oxidizing agent. Then we create an electronic balance.

S -2 -6e - →S +4 2 - multiplication factor for the reducing agent

O 2 +4e - →2O -2 3 - multiplication factor for the oxidizing agent

We write the formulas of substances taking into account multiplication coefficients

2H 2 S+ 3O 2 = 2SO 2 +2H 2 O

Let's consider another case - the decomposition of aluminum nitrate Al(NO 3) 3. In this substance, nitrogen atoms have the highest oxidation state (+5), and oxygen atoms have the lowest (-2). It follows that nitrogen will be an oxidizing agent, and oxygen will be a reducing agent. We draw up an electronic balance, knowing that all nitrogen is reduced to nitrogen dioxide, and oxygen is oxidized to molecular oxygen. Taking into account the numbers of atoms, we write:

3N +5 +3e - → 3N +4 4

2O -2 -4e - →O 2 o 3

then the decomposition equation will be written as follows: 4Al(NO 3) 3 = Al 2 O 3 + 12NO 2 + 3O 2.

Method electronic balance usually used to determine coefficients in ORR occurring in heterogeneous systems containing solids or gases.

For reactions occurring in solutions, it is usually used electron-ion balance method, which takes into account the influence of various factors on the composition of the final products.

This method takes into account: a) the acidity of the medium, b) the concentration of reacting substances, c) the actual state of the reacting particles in solution, d) the influence of temperature, etc. In addition, for this method there is no need to use the oxidation state.

Many substances have special properties, which in chemistry are usually called oxidizing or reducing.

Some chemical substances exhibit the properties of oxidizing agents, others - reducing agents, while some compounds can exhibit both properties simultaneously (for example, hydrogen peroxide H 2 O 2).

What are oxidizing and reducing agents, oxidation and reduction?

The redox properties of a substance are associated with the process of giving and receiving electrons by atoms, ions or molecules.

An oxidizing agent is a substance that accepts electrons during a reaction, i.e., is reduced; reducing agent - gives up electrons, i.e. oxidizes. The processes of transferring electrons from one substance to another are usually called redox reactions.

Compounds containing atoms of elements with the maximum oxidation state can only be oxidizing agents due to these atoms, because they have already given up all their valence electrons and are only able to accept electrons. The maximum oxidation state of an element's atom is equal to the number of the group in the periodic table to which the element belongs. Compounds containing atoms of elements with a minimum oxidation state can only serve as reducing agents, since they are only capable of donating electrons, because the outer energy level of such atoms is completed by eight electrons

hair oxidizer, thuya oxidizer
Oxidizer- a substance that contains atoms that join during chemical reaction electrons, in other words, the oxidizing agent is an electron acceptor.

Depending on the task at hand (oxidation in the liquid or gaseous phase, oxidation on the surface), a variety of substances can be used as an oxidizing agent.

• Electrochemical oxidation allows you to oxidize almost any substance at the anode, in solutions or in melts. Thus, the strongest inorganic oxidizing agent, elemental fluorine, is obtained by electrolysis of fluoride melts.

• 1 Common oxidizing agents and their products
• 2 Mnemonic rules
• 3 Dependence of the degree of oxidation on the concentration of the oxidizing agent
• 4 Strong oxidizing agents
• 5 Very strong oxidizing agents
• 6 See also

Common oxidizing agents and their products

Mnemonic rules

There are several mnemonic rules for remembering the properties of oxidizing agents and reducing agents:

1. The oxidizing agent is a robber (during the redox reaction, the oxidizing agent gains electrons).
2. Association with a familiar word: PVO - Attaches (electrons), Reduces, is an Oxidizing Agent.
3. Gives away - it oxidizes, it itself is a reducing agent.

Dependence of the degree of oxidation on the concentration of the oxidizing agent

How metal is more active, reacting with acid, and the more dilute its solution, the more complete the reduction. As an example, the reaction of nitric acid with zinc:

• Zn + 4HNO3(conc.) = Zn(NO3)2 + 2NO2 + 2H2O
• 3Zn + 8HNO3(40%) = 3Zn(NO3)2 + 2NO + 4H2O
• 4Zn + 10HNO3(20%) = 4Zn(NO3)2 + N2O + 5H2O
• 5Zn + 12HNO3(6%) = 5Zn(NO3)2 + N2 + 6H2O
• 4Zn + 10HNO3(0.5%) = 4Zn(NO3)2 + NH4NO3 + 3H2O

Strong oxidizing agents

“Aqua regia”, a mixture of one volume of nitric acid and three volumes of hydrochloric acid, has strong oxidizing properties.

HNO3 + 3HCl ↔ NOCl + 2Cl + 2H2O

The nitrosyl chloride formed in it decomposes into atomic chlorine and nitrogen monoxide:

Aqua regia is a strong oxidizing agent due to the atomic chlorine that forms in the solution. Aqua regia oxidizes even noble metals - gold and platinum.

Another strong oxidizing agent is potassium permanganate. It is capable of oxidizing organic substances and even breaking carbon chains:

С6H5-CH2-CH3 + → C6H5COOH + … C6H6 + → HOOC-(CH2)4-COOH

The strength of an oxidizing agent in a reaction in a dilute aqueous solution can be expressed by the standard electrode potential: the higher the potential, the stronger the oxidizing agent.

Very strong oxidizing agents

Conventionally, “very strong oxidizing agents” include substances that exceed molecular fluorine in oxidative activity. These include, for example, platinum hexafluoride, dioxydifluoride, krypton difluoride, potassium hexafluoronickelate(IV). The listed substances, for example, are capable of oxidizing the inert gas xenon at room temperature, which fluorine is unable to do (pressure and heating are required), and especially not any of the oxygen-containing oxidizers.

see also

• Redox reactions

thuya oxidizer, hair oxidizer, senko oxidizer, oxidizer it, oxidation tower, oxidative number, oxidative enzymes, oxidative stress

Oxidizer Information About

Many women like to regularly update their hair color. In addition to classic paint, it is necessary to use an oxidizing agent. This will allow you to get a rich shade. What is an oxidizing agent? The product is necessary for the dye to act on the hair and for it to acquire the desired tone. Without the use of an oxidizing agent, you will not get an excellent result.

The most important substance is hydrogen peroxide, the content of which in the oxidizing agent may vary. Typically this figure is 1.8-12%. If the component is present in an amount of up to 2%, then the cosmetics are gentle. The paint will not perform long-term staining.

Types of oxidizing agents

Several oxidizers containing 3, 6 and 9% are bottled. The remedies are classified as classic:

• With 3% you can dye your hair a natural shade, lighten or darken it a little.
• 6% peroxide will allow you to change your hair color by 2 tones, as well as cover gray hair and red hair.
• What is an oxidizing agent with 9%? With the product you can cover coarse hair and gray hair, resulting in a rich color.

Each package indicates how much hydrogen peroxide. But you should not rely entirely on this data, since the effect may vary. The oxidizing agent is also used to wash off the paint if the shade turns out to be unattractive.

Paint remover

What is a rinse-off agent? This is the same product, only it allows you to remove the ugly color. The concentration of the composition for rinsing is more than 12%. The product is applied to the curls with a comb, and after the time specified in the procedure, you can wash them with shampoo.

Often this procedure should not be performed so as not to damage the hair. Dye oxidizer can make strands dry. After dyeing, you need to use a balm that has a softening effect.

Proportions

It is important to know not only what an oxidizing agent is, but also how it is used. Usually on the paint packaging it is indicated in what ratios the components should be mixed. If the hair oxidizer is sold separately, the instructions for use will be indicated on the tube. If a bright color is required, then mixing in equal proportions is necessary. The number of components depends on the type of product.

The proportions should not be violated, otherwise it may lead to a negative result. When the oxidizing agent is contained in smaller quantities, the color will not be saturated. This will not hide gray hair. Too much dye causes your hair to become coarse. And recovery takes quite a long time. You should also not use paint without an oxidizing agent, since it has no effect.

Breeding rules

During the procedure, it is important not to harm the curls. And if they were weakened before, then many recovery sessions will be required. To do everything correctly, you need to properly mix the developer and paint. Please read the included instructions first.

If the paint contains oil components, it is important to consider that such products cannot be used with peroxide. When using professional paints, you need to check your skin for allergies. The finished product should be applied to the wrist, and then watch the reaction. In case of folding, this composition is not suitable.

The oxidizer "Estelle" is included in the kit detailed instructions, so you get a quality product. It is advisable to use a plastic, ceramic or glass container to mix the components. First the oxidizing agent is added, and then the paint. The components must be thoroughly mixed to obtain a homogeneous mass. It is better to use a special brush.

To obtain a high-quality dyeing mixture, you need to use products from the same company. If everything is done correctly, you will get a rich color. It is also not worth adding other components, since the result is unpredictable.

It is advisable to take an oxidizer for hair dye with a peroxide content of 6-7.5%. You should choose 2 packs of paint if your hair is long. There is no need to feel sorry, because only then will you get a rich tone. But the brightest color will be if the composition contains an oxidizing agent and ammonia.

Features of choice

It is necessary to buy products from one company, because this will give you a high-quality result. By correctly calculating the proportions, you will guess and your hair will acquire the desired shade. Products from different manufacturers can bring unexpected results. You can purchase components as a set or separately.

You need to check if the color is suitable. It may differ slightly from what is indicated on the package. It is important to know the expiration date, since an expired product will not bring the desired result. Moreover, it can damage your hair.

It is advisable to take products from proven brands that are used repeatedly. For the procedure, you need to purchase special tools if they are not included in the kit. The product must maintain the integrity of its packaging.

Cost and types of companies

The price of the components is in the range of 300-500 rubles. Manufacturers who produce paint as a set also sell the components separately. Some women find this comfortable. One product is often enough for 2 procedures.

Matrix is ​​on sale. This product will not produce a rich tone, so it is used to maintain the shade. The matrix is ​​not suitable for covering gray hair. There is professional paint "Selective", which has a rich palette. "Estelle" paint is also a quality paint.

It is advisable to buy products from professional brands. In this case, the hair retains its natural structure and is therefore slightly damaged. The oxidizer "Matrix" costs about 700 rubles, and "Kutrin" - 500. The right product will perfectly renew your hair color.