Oxidation of isopropylbenzene permanganate potassium in an alkaline medium. Redox reactions involving organic substances
St. Petersburg State Technological Institute
(Technical University)
Department of Organic Chemistry Faculty 4
Group 476.
Course work
Oxidation of alkenes
Student ............................................. Rytin A.I.
Lecturer .................................... ... St. Petersburg Yu.L.
St. Petersburg
Introduction
1.Epoxidation (reaction N.A. Prilezhev, 1909)
2. Hydroxilization
2.1anti -Hhydroxylation
2.2syn -Hhydroxylation
3. Ovicultive splitting of alkenes
4.Osomolysis
5. Society of alkenes in the presence of palladium salts
Conclusion
List of sources used
Introduction
Oxidation is one of the most important and common transformations of organic compounds.
Under oxidation in organic chemistry, the processes leading to depletion of compounds with hydrogen or enrichment with its oxygen. In this case, the electron molecule takes place. Accordingly, the restoration understand the separation from the organic oxygen molecule or the hydrogen attachment to it.
In oxidative-reducing reactions, oxidizers are compounds with a large affinity for an electron (electrophila), and reducing agents - compounds that have a tendency to return electrons (nucleophiles). The ease of oxidation of the compound increases with the growth of its nucleophilicity.
When oxidizing organic compounds, as a rule, the total transmission of electrons and, accordingly, changes in the valence of carbon atoms does not occur. Therefore, the concept of the degree of oxidation is the conditional charge of an atom in the molecule, calculated, based on the assumption that the molecule consists only of ions - is only conditional, formal character.
In the preparation of the equations of redox reactions, it is necessary to determine the reducing agent, the oxidizing agent, and the number of devoted and received electrons. As a rule, the coefficients are selected using the electron-ion balance method (half-formation method).
In this method, the transition of electrons from one atoms or ions to another, taking into account the nature of the medium (acid, alkaline or neutral), in which the reaction proceeds. To equalize the number of oxygen and hydrogen atoms or water molecules and protons (if the sour medium), or water molecules and hydroxide ions (if alkaline) is introduced.
Thus, when writing semitractions of recovery and oxidation, it is necessary to proceed from the composition of the ions that are in solution. Malodissions, poorly soluble or gas released in the form of gas should be written in molecular form.
As an example, consider the process of ethylene oxidation by a dilute aqueous solution of potassium permanganate (Wagner reaction). In the course of this reaction, ethylene is oxidized to ethylene glycol, and potassium permanganate is restored to manganese dioxide. At the dual connection, two hydroxyl are joined:
3C 2 H 4 + 2KMNO 4 + 4H 2 O → 3C 2 H 6 O 2 + 2MNO 2 + 2KOH
Semi-reaction recovery: MNO 4 ¯ + 2H 2 O + 3 e. → MNO 2 + 4OH ¯ 2Oxidation semi-reaction: C 2 H 4 + 2OH - - 2 e. → C 2 H 6 O 2 3
Finally we have in ion form:
2mno 4 ¯ + 4H 2 O + 3C 2 H 4 + 6OH ¯ → 2mno 2 + 8OH ¯ + 3C 2 H 6 O 2
After carrying out the necessary cuts of such members, write the equation in molecular form:
3C 2 H 4 + 2Kmno 4 + 4 H 2 O \u003d 3C 2 H 6 O 2 + 2MNO 2 + 2KOH.
Characteristic of some oxidizing agents
Oxygen
Air oxygen is widely used in technological processes, as it is the cheapest oxidant. But the oxygenation of air oxygen is associated with the difficulties associated with the control of the process, which flows in different directions. Oxidation is usually carried out at high temperatures in the presence of catalysts.
Ozone
Ozone O 3 is used to obtain aldehydes and ketones if they are difficult to obtain in other ways. Most often, ozone is used to establish the structure of unsaturated compounds. Ozone is obtained under the action of a quiet electric discharge on oxygen. One of the substantial advantages of ozonization, compared with chlorination, is the absence of toxins after processing.
Potassium permanganate
Permanganate potassium is the most frequently used oxidizing agent. The reagent is soluble in water (6.0% at 20 ° C), as well as in methanol, acetone and acetic acid. For oxidation, aqueous (sometimes acetone) solutions KMNO 4 in a neutral, acid or alkaline medium are used. When conducting a process in a neutral medium, magnesium, aluminum, or carbon dioxide is added to the neutralization of potassium-released hydroxide, is added to the reaction mass. The oxidation reaction of KMNO 4 in an acidic medium is most often carried out in the presence of sulfuric acid. The alkaline medium in oxidation creates the KOH generated during the reaction, or it is initially added to the reaction mass. In weakly alkaline and neutral media, KMNO 4 oxidizes by equation:
KMNO 4 +. 3 e. + 2H 2 O \u003d k + + MnO 2 + 4OH ¯
in an acidic environment:
KMNO 4 +. 5 e. + 8h + \u003d k + + mn 2+ + 4h 2 o
Potassium permanganate is used to obtain 1,2-diols from alkenes, with oxidation of primary alcohols, aldehydes and alkylarens to carboxylic acids, as well as for oxidative splitting of the carbon skeleton across multiple bonds.
In practice, quite large excess (more than 100%) KMNO 4 is usually used. This is explained by the fact that under normal conditions KMNO 4 partially decomposes on manganese dioxide with the release of O 2. Decomposed concentrated H 2 SO 4 when heated in the presence of rebuilders with an explosion; Mixtures of potassium permanganate with organic substances are also explosives.
Nadkislot
Peracetic and permaraye acids are obtained by a reaction of 25-90% hydrogen peroxide with an appropriate carboxylic acid according to the following reaction:
RCOOH + H 2 O 2 \u003d RCOOOH + H 2 O
In the case of acetic acid, this equilibrium is set relatively slowly, and to accelerate the formation of peaks usually add sulfuric acid as a catalyst. The formic acid is strong enough by itself in order to ensure the rapid establishment of equilibrium.
Penrophunturuce acid obtained in a mixture with trifluoroacetic acid reaction of trifluoroacetic anhydride with 90% hydrogen peroxide, an even stronger oxidizer. Similarly, perussic acid can be obtained from acetic anhydride and hydrogen peroxide.
Especially popular firm m. -Hlorperbenzoic acid, since it is relatively safe in circulation, it is fairly stable and can be stored for a long time.
Oxidation occurs due to the released oxygen atom:
Rcoooh \u003d rcoh + [o]
Nadcisitles are used to obtain epoxides from alkenes, as well as lactones from alicyclic ketones.
Hydrogen peroxide
Hydrogen peroxide is a colorless liquid, mixed with water, ethanol and diethyl ether. A 30% solution H 2 O 2 is called perhydro. The highly concentrated drug can react with organic substances with an explosion. When storing decomposes on oxygen and water. The resistance of hydrogen peroxide increases with dilution. For oxidation, aqueous solutions of various concentrations are used (from 3 to 90%) in neutral, acidic or alkaline media.
H 2 O 2 \u003d H 2 O + [O]
The action of this reagent on α, β-uninhabited carbonyl compounds in the alkaline medium is obtained by appropriate epoxyaldehydes and ketones, the oxidation of carboxylic acids in the acidic medium is synthesized. A 30% solution H 2 O 2 in acetic acid oxidizes alkenes in 1,2-diol. Hydrogen peroxide is used: to obtain organic and inorganic peroxides, pebble and percarbonate Na; as an oxidizing agent in rocket fuels; in the preparation of epoxides, hydroquinone, pyrocatechin, ethylene glycol, glycerin, vulcanization accelerators of the group of Tyurama et al.; for whitening oils, fats, fur, leather, textile materials, paper; for cleaning germanium and silicon semiconductor materials; as a disinfectant for disposal of household and industrial wastewater; in medicine; as a source of 2 in submarines; H 2 O 2 is part of the fenton reagent (Fe 2 + H 2 O 2), which is used as a source of free radicals in organic synthesis.
Ruthenium Tetraxides and Osmia
Tetraoxide Osmia OSO 4 - powder from white to pale yellow color with t. Pl. 40.6ºС; t. Kip. 131.2ºС. It is removed at room temperature, soluble in water (7.47 g of 100 ml at 25 ° C), CCl 4 (250 g of 100 g of solvent at 20 ° C). In the presence of organic compounds, blacksmith due to the restoration to OSO 2.
RUO 4 is a golden yellow prism with t. Pl. 25.4ºС, it is noticeably accomplished at room temperature. Moderately soluble in water (2.03 g per 100 ml at 20 ° C), very well soluble in CCL 4. Strong oxidizer than OSO 4. Above 100ºС explodes. As well as osmium tetraoxide has large toxicity and high cost.
These oxidizers are used for oxidation of alkenes in α-glycols in mild conditions.
As already mentioned, the oxidation of the organic matter is the introduction of oxygen into its composition and (or) the cleavage of hydrogen. Recovery - reverse process (injection of hydrogen and oxygen cleavage). Considering the composition of alkanans (CNH2N + 2), it can be concluded about their inability to join the reaction of recovery, but the ability to participate in oxidation reactions.
Alkaans - compounds with low degrees of carbon oxidation, and depending on the reaction conditions, they can oxidize with the formation of various connections.
At normal temperature, alkanes do not react even with strong oxidizing agents (H2Cr2O7, KMNO4, etc.). When introduced into the open flame, Alkana is burning. In this case, in the excess of oxygen, their complete oxidation takes place to CO2, where carbon has the highest degree of oxidation +4, and water. The burning of hydrocarbons leads to the rupture of all C-C and C-H connections and is accompanied by the release of a large amount of heat (exothermic reaction).
It is generally accepted that the mechanism of alkanan oxidation includes a radical chain process, since oxygen itself is mad-absorbable in order to tear the hydrogen atom from alkane, a particle is needed, which will initiate the occurrence of an alkyl radical that will react with oxygen, giving peroxyradical. Then the peroxyradecal may tear the hydrogen atom from another alkane molecule to form alkylhydroper oxide and radical.
It is possible to oxidizing alkanes with air oxygen at 100-150 ° C in the presence of a catalyst - manganese acetate, this reaction is applied in industry. Oxidation occurs when the air current is purned through the melted paraffin containing the solder of manganese.
Because As a result of the reaction, a mixture of acids is formed, they are separated from unreacted paraffin with dissolution in aqueous alkali, and then neutralized by mineral acid.
Directly in industry, this method is used to obtain acetic acid from H-Bhutan:
Oxidation of alkenes
Alkene oxidation reactions are divided into two groups: 1) reactions in which the carbon skeleton, 2) of the reaction of the oxidative destruction of the carbon skeleton of the double-bond molecule is preserved.
The oxidation reactions of alkenes while maintaining a carbon skeleton
1. Epoxidation (Priary Reaction)
Acyclic and cyclic alkenes when interacting with peracids in a non-polar medium form epoxides (oxirans).
Also, oxyranes can be obtained by oxidizing alkenes by hydroperoxides in the presence of molybdenum, tungsten-, vanadium-containing catalysts:
The simplest oxiran - ethylene oxide - is obtained in industry by oxidation by oxygen in the presence of silver or silver oxide as a catalyst.
2. Anti-hydroxylation (hydrolysis of epoxides)
Acid (or alkaline) hydrolysis of epoxides leads to an oxide cycle disclosure with the formation of transduits.
In the first stage, the epoxide oxygen atom is protonated to the formation of a cyclic oxonium cation, which is revealed as a result of a nucleophilic attack of water molecule.
The disclosure of the epoxy ring catalyzed by the base also leads to the formation of trans-glycols.
3. Sin-hydroxylation
One of the oldest oxidation methods of alkenes is the Wagner reaction (potassium permanganate oxidation). Initially, the oxidation is formed by a cyclic ether of manganese acid, which is hydrolyzed to the Vicinal Diola:
In addition to the Wagner reaction there is another method of symbol-hydroxylation of alkenes under the action of Osmia oxide (VIII), which was proposed by a Creek. Under the action of tetraoxide, the osmium on alkene on ether or dioxane is formed black precipitate of osmisic acid cyclic ester - osmat. However, the addition of OSO4 to multiple communication is noticeably accelerated in pyridine. The resulting black precipitate of osmat is easily decomposed by the action of the aqueous solution of sodium hydrosulfite:
Potassium permanganate or Osmia oxide (VIII) oxidize alken to cis-1,2-diol.
Oxidative splitting of alkenes
The oxidative splitting of alkenes includes the reactions of interaction with potassium permanganate in alkaline or in sulfuric acid, as well as the oxidation of chromium trioxide solution in acetic acid or potassium dichromate and sulfuric acid. The end result of such transformations is the splitting of the carbon skeleton at the dual bond and the formation of carboxylic acids or ketones.
Disament alkenes with terminal double bonds are split to carboxylic acid and carbon dioxide:
If both carbon atoms at a double bond comprise only one alkyl group, a mixture of carboxylic acids is formed:
But if the tetrazhesty-dual connection is alken - ketone:
The reaction of ozonolysis alkenes has been developed much more preparative importance. For many decades, this reaction served as the main method of determining the structure of the original alkene. This reaction is carried out by passing the current of the ozone solution in oxygen alkane solution in methylene chloride or ethyl acetate at -80 ... -100 ° C. The mechanism of this reaction is set to Cryga:
Ozonides are unstable compounds that decompose with the explosion. There are two ways of decomposition of ozonides - oxidative and reducing.
In the hydrolysis of ozonides, they are split into carbonyl compounds and hydrogen peroxide. Hydrogen peroxide oxidizes aldehyde to carboxylic acids - this is an oxidizing decomposition:
A reducing splitting of ozonidov is much more important. Aldehydes or ketones are found as ozonelysis products depending on the structure of the original alkene:
In addition to the above methods, there is another method proposed in 1955. LEMIDE:
In the Lemye method, there is no labor-intensive procedures for the separation of manganese dioxide, because Dioxide and manganate are again oxidized by periodate to permanganate ion. This allows you to use only the catalytic quantity of potassium permanganate.
18. Redox reactions (continued 2)
18.9. OSR with the participation of organic substances
In the OSR organic substances with inorganic organic substances are most often reducing agents. Thus, when combustion of organic matter, carbon dioxide and water is always formed in excess oxygen. It is more complicated by reactions when using less active oxidizers. In this paragraph, only the reactions of representatives of the most important classes of organic substances with some inorganic oxidizers are considered.
Alkenes. With the soft oxidation of alkenes turn into glycols (diatomic alcohols). Atoms-reducing agents in these reactions - carbon atoms associated with double bond.
The response with potassium permanganate solution takes place in a neutral or weakly alkaline medium as follows:
C 2 H 4 + 2KMNO 4 + 2H 2 O CH 2 OH-CH 2 OH + 2MNO 2 + 2KOH (Cooling)
In more stringent conditions, oxidation leads to a discontinuation of a carbon chain for a double bond and the formation of two acids (in a strongly alkaline medium - two salts) or acid and carbon dioxide (in a strongly alkaline environment - salts and carbonate):
1) 5ch 3 CH \u003d CHCH 2 CH 3 + 8KMNO 4 + 12H 2 SO 4 5CH 3 COOH + 5C 2 H 5 COOH + 8MNSO 4 + 4K 2 SO 4 + 17H 2 O (Heating)
2) 5ch 3 CH \u003d CH 2 + 10KMNO 4 + 15H 2 SO 4 5CH 3 COOH + 5CO 2 + 10MNSO 4 + 5K 2 SO 4 + 20H 2 O (Heating)
3) CH 3 CH \u003d CHCH 2 CH 3 + 6KMNO 4 + 10KOH CH 3 Cook + C 2 H 5 Cook + 6H 2 O + 6K 2 MNO 4 (Heating)
4) CH 3 CH \u003d CH 2 + 10KMNO 4 + 13KOH CH 3 Cook + K 2 CO 3 + 8H 2 O + 10K 2 MNO 4 (Heating)
Potassium dichromat in the sulfuric acid medium oxidizes alkenes in similarly reactions 1 and 2.
Alkina. Alkins begin to oxidize in a slightly more stringent conditions than alkenes, so they are usually oxidized with a tip of a carbon chain along a triple bond. As in the case of alkanes, the reducing atoms here are carbon atoms associated in this case by the triple bond. As a result of the reactions, acids and carbon dioxide are formed. Oxidation can be carried out by permanganate or potassium dichromate in an acidic environment, for example:
5CH 3 C CH + 8KMNO 4 + 12H 2 SO 4 5CH 3 COOH + 5CO 2 + 8MNSO 4 + 4K 2 SO 4 + 12H 2 O (Heating)
Sometimes it is possible to allocate intermediate oxidation products. Depending on the position of the triple bond in the molecule, these or diketones (R 1 -CO-CO-R 2), or alochetons (R-CO-CHO).
Acetylene can be oxidized by potassium permanganate in a slightly allegum to potassium oxalate:
3C 2 H 2 + 8KMNO 4 \u003d 3K 2 C 2 O 4 + 2H 2 O + 8MNO 2 + 2KOH
In an acidic environment, oxidation goes to carbon dioxide:
C 2 H 2 + 2KMNO 4 + 3H 2 SO 4 \u003d 2CO 2 + 2MNSO 4 + 4H 2 O + K 2 SO 4
Gomezol homologs. Benzole homologs can be oxidized by potassium permanganate solution in a neutral medium to potassium benzoate:
C 6 H 5 CH 3 + 2KMNO 4 \u003d C 6 H 5 Cook + 2mnO 2 + KOH + H 2 O (boiling)
C 6 H 5 CH 2 CH 3 + 4KMNO 4 \u003d C 6 H 5 Cook + K 2 CO 3 + 2H 2 O + 4MNO 2 + KOH (when heated)
The oxidation of these substances by dichromate or permanganate potassium in the acidic medium leads to the formation of benzoic acid.
Alcohols. The direct product of the oxidation of primary alcohols is aldehydes, and secondary - ketones.
The aldehyde alcohols formed during the oxidation are easily oxidized to acids, therefore the aldehydes from the primary alcohols are obtained by oxidation of potassium dichromate in the acidic medium at a boiling point of aldehyde. Evaporated, aldehydes do not have time to oxidize.
3C 2 H 5 OH + K 2 CR 2 O 7 + 4H 2 SO 4 \u003d 3CH 3 CHO + K 2 SO 4 + CR 2 (SO 4) 3 + 7H 2 O (Heating)
With an excess of oxidizing agent (KMNO 4, k 2 Cr 2 O 7) in any medium, primary alcohols are oxidized to carboxylic acids or their salts, and secondary to ketones. Tertiary alcohols under these conditions are not oxidized, and methyl alcohol is oxidized to carbon dioxide. All reactions go when heated.
Double alcohol, ethylene glycol HOCH 2 -CH 2 OH, when heated in an acidic medium with a solution of KMNO 4 or K 2 CR 2 O 7, it is easily oxidized to carbon dioxide and water, but sometimes it is possible to allocate intermediate products (HOCH 2 -COOH, HOOC- COOH, etc.).
Aldehydes. Aldehydes are quite strong reducing agents, and therefore are easily oxidized by various oxidizing agents, for example: KMNO 4, K 2 Cr 2 O 7, OH. All reactions come when heated:
3ch 3 cho + 2kmno 4 \u003d CH 3 COOH + 2CH 3 Cook + 2mno 2 + H 2 O
3CH 3 CHO + K 2 CR 2 O 7 + 4H 2 SO 4 \u003d 3CH 3 COOH + CR 2 (SO 4) 3 + 7H 2 O
CH 3 CHO + 2OH \u003d CH 3 COONH 4 + 2AG + H 2 O + 3NH 3
Formaldehyde with an excess of the oxidizer is oxidized to carbon dioxide.
18.10. Comparison of the oxidation and reducing activity of various substances
Of the definitions of the concepts "atom-oxidizer" and "atom-reducing agent" it follows that only oxidizing properties have atoms in the highest oxidation. On the contrary, atoms in the lowest oxidation are reducing the reducing properties. Atoms that are in intermediate degrees of oxidation can be both oxidizing agents and reducing agents.
At the same time, based on the degree of oxidation, it is impossible to unequivocally assess the redox properties of substances. As an example, consider connections to the elements of the VA group. Nitrogen compounds (V) and antimony (V) are more or less strong oxidizers, bismuth compounds (V) are very strong oxidizers, and phosphorus compounds (V) with oxidizing properties practically do not possess. In this and other similar cases, it is important as far as this degree of oxidation is characteristic of this element, that is, how much the compound containing atoms of this element in this degree of oxidation.
Any OSR flows towards the formation of a weaker oxidizing agent and a weaker reducing agent. In general, the possibility of leakage of any OSR, as well as any other reaction, can be determined by the sign of changing the energy of Gibbs. In addition, an electrochemical characteristics of oxidizing agents and reducing agents (standard potentials of redox recovery pairs) are used to quantify the oxidation and reducing activity of substances. Based on these quantitative characteristics, we can construct rows of the redox activity of various substances. A number of metal voltages known to you are constructed in this way. This series makes it possible to compare the reductive properties of metals in aqueous solutions under standard conditions ( from \u003d 1 mol / l, T. \u003d 298.15 K), as well as the oxidative properties of simple aquacatones. If in the upper line of this series, put ions (oxidizing agents), and in the bottom - atoms of metals (reducing agents), then the left side of this series (to hydrogen) will look like this:
In this row, the oxidative properties of ions (top row) are enhanced from left to right, and the rehabilitation properties of metals (lower line), on the contrary, to the right left.
Given the differences in redox activity in different environments, you can build similar rows and for oxidizing agents. So, for reactions in the acidic medium (pH \u003d 0), a "continuation" of a number of metals activity in the direction of amplification of oxidative properties is obtained
As in a number of metal activity, the oxidative properties of oxidizing agents (top row) are enhanced from left to right. But using this series, to compare the restorative activity of the reducing agents (the lower line) is only possible when their oxidized form coincides with the top string; In this case, it enhances the right left.
Consider several examples. To find out whether this OSR is possible to use a general rule that determines the direction of flow of redox reactions (reactions flow in the direction of formation of a weaker oxidant and a weaker reducing agent).
1. Is it possible to restore cobalt from COSO 4 solution to magnesium?
Magnesium is a stronger reducing agent than cobalt, and CO 2 ions are stronger oxidizers than MG 2 ions, therefore, you can.
2. Is it possible to oxidize copper to CUCl 2 in acidic medium?
Since FE 3B ions are stronger oxidizers than Cu 2 ions, and copper is a stronger reducing agent than Fe 2 ions, then you can.
3. Is it possible, blowing oxygen through the acidic acid acidic acid solution 2, to obtain a solution of FECL 3?
It would seem no, since in our row oxygen it is the left of the FE 3 ions and is a weaker oxidant than these ions. But in an aqueous solution, oxygen is almost never restored to H 2 O 2, in this case it is restored to H 2 O and occupies a place between Br 2 and MnO 2. Consequently, such a reaction is possible, however, it flows quite slowly (why?).
4. Can potassium permanganate oxidize H 2 O 2 in the acidic medium?
In this case, H 2 O 2, the reducing agent and the reducing agent is stronger than Mn 2B ions, and MNO 4 ions are stronger than the oxygen forming from peroxide. Therefore, it is possible.
A similar range, built for OSR in an alkaline medium, is as follows:
Unlike the "acid" series, this series cannot be used in conjunction with a number of activity of metals.
Method of electron-ion balance (semi-resource method), intermolecular OSR, intramolecular OSR, dysmutation ORV (disproportionation, self-healing-self-healing), Primutation, passivation.
- Using the electron-ion balance method, make the equations of reactions flowing down when adding potassium permanent solution of potassium a) H 2 S (s, more precisely, S 8) when added to acidified sulfuric acid. b) khs; c) k 2 s; d) H 2 SO 3; e) khso 3; e) k 2 SO 3; E) hno 2; g) kno 2; and) ki (i 2); K) FESO 4; l) C 2 H 5 OH (CH 3 COOH); m) CH 3 CHO; H) (COOH) 2 (CO 2); P) K 2 C 2 O 4. Here and further in the necessary cases in curious brackets are oxidation products.
- Make the equations of reactions flowing at the passage of the following gases through a sulfuric acid acid solution of potassium permanganate: a) C 2 H 2 (CO 2); b) C 2 H 4 (CO 2); c) C 3 H 4 (Propin) (CO 2 and CH 3 COOH); d) C 3 H 6; e) ch 4; e) hcho.
- The same, but the reductant solution is added to the neutral solution of potassium permanganate: a) KHS; b) k 2 s; c) khso 3; d) k 2 SO 3; e) kno 2; e) ki.
- The same, in a solution of potassium permanganate, a solution of potassium hydroxide was pre-added: a) k 2 S (K 2 SO 4); b) k 2 SO 3; c) KNO 2; d) ki (KIO 3).
- Make the equations of the following reactions flowing in the solution: a) KMNO 4 + H 2 S ...;
b) KMNO 4 + HCl ...;
c) KMNO 4 + HBR ...;
d) KMNO 4 + Hi ... - Make the following MARGAN DIOXIDE equations:
- The solutions of the following substances are added to the acidic acid acid solution of potassium dichromate: a) KHS; b) k 2 s; c) hno 2; d) kno 2; e) ki; e) FESO 4; g) CH 3 CH 2 CHO; and) H 2 SO 3; k) khso 3; L) K 2 SO 3. Make the equations of occurring reactions.
- The same, but the following gases are passed through the solution: a) H 2 S; b) SO 2.
- To the solution of potassium chromate containing potassium hydroxide, solutions a) k 2 s (K 2 SO 4) are added; b) k 2 SO 3; c) KNO 2; d) ki (KIO 3). Make the equations of occurring reactions.
- A solution of potassium hydroxide hydroxide solution was added to the solution of chromium chromium (III) to dissolve the sediment's originally formed, and then bromine water. Make the equations of occurring reactions.
- The same, but at the last stage, a solution of potassium peroxodisulfate K 2 S 2 O 8 was added, recovered during the reaction to sulfate.
- Make the equations of reactions flowing in the solution:
- Make the equations of reactions occurring between the solid chromium trioxide and the following substances: a) c; b) co; c) S (SO 2); d) h 2 s; e) NH 3; e) C 2 H 5 OH (CO 2 and H 2 O); g) CH 3 COCH 3.
- Make the equations of reactions occurring when adding substances to concentrated nitric acid: a) S (H 2 SO 4); b) p 4 ((HPO 3) 4); c) graphite; d) SE; d) i 2 (hio 3); e) ag; g) Cu; and) PB; k) kf; l) FEO; m) fes; n) mgo; n) mgs; p) Fe (OH) 2; c) p 2 O 3; T) AS 2 O 3 (H 3 ASO 4); y) AS 2 S 3; f) FE (NO 3) 2; x) p 4 O 10; c) Cu 2 S.
- The same, but when passing the following gases: a) CO; b) h 2 s; c) n 2 o; d) NH 3; e) no; e) H 2 SE; g) Hi.
- Equally, or in different ways will be reactions in the following cases: a) into a high tube for two thirds filled with concentrated nitric acid, placed a piece of magnesium; b) A drop of concentrated nitric acid was placed on the magnesium plate surface? Make the reaction equations.
- What is the difference between the reaction of concentrated nitric acid with hydrogen sulfide acid and with a gaseous hydrogen sulfide? Make the reaction equations.
- Will the OSR be equally located when the anhydrous crystalline sodium sodium sulfide and its 0.1 m solution is added to a concentrated solution of nitric acid?
- The mixture of the following substances was treated with concentrated nitric acid: Cu, Fe, Zn, Si and CR. Make the equations of occurring reactions.
- Make the equations of reactions occurring when the following substances in dilute nitric acid are added: a) i 2; b) mg; c) Al; d) Fe; e) feo; e) fes; g) FE (OH) 2; and) FE (OH) 3; k) MNS; l) Cu 2 S; m) cus; n) cuo; n) Na 2 s cr; p) Na 2 s p; c) p 4 O 10.
- What processes will flow when passing an ammonia, b) hydrogen sulfide, c) of carbon dioxide?
- Make the equations of reactions occurring when adding substances to concentrated sulfuric acid: a) AG; b) Cu; c) graphite; d) hcooh; d) with 6 H 12 O 6; e) naCl kr; g) C 2 H 5 Oh.
- When passing through a cold concentrated sulfide hydrogen sulfide, S and SO 2 is formed, the hot concentrated H 2 SO 4 oxidizes sulfur to SO 2. Make the reaction equations. How will the reaction between the hot concentrated H 2 SO 4 and hydrogen sulfide?
- Why hydrogen garden is obtained by treating crystalline sodium chloride with concentrated sulfuric acid, and the bromomarodine and iodine hydrogen are not received in this way?
- Make the equations of reactions occurring in the interaction of dilute sulfuric acid C a) Zn, b) Al, c) Fe, d) chrome in the absence of oxygen, e) chrome in air.
- Make the equations of reactions characterizing the oxidation and reduction properties of hydrogen peroxide:
- What reactions occur when heating the following substances: a) (NH 4) 2 CRO 4; b) Nano 3; c) Caco 3; d) Al (NO 3) 3; e) Pb (NO 3) 3; e) agno 3; g) Hg (NO 3) 2; and) Cu (NO 3) 2; k) cuo; l) Naclo 4; m) Ca (CLO 4) 2; H) Fe (NO 3) 2; P) PCL 5; p) MnCl 4; c) H 2 C 2 O 4; T) LINO 3; y) hgo; f) Ca (NO 3) 2; x) Fe (OH) 3; c) CUCL 2; h) KCLO 3; W) KCLO 2; Sh) Cro 3?
- In the merging of hot solutions of ammonium chloride and potassium nitrate proceeds, accompanied by gas release. Make the equation of this reaction.
- Make the equations of reactions occurring by passing through a cold solution of sodium hydroxide a) chlorine, b) bromine vapors. The same, but through a hot solution.
- When interacting with a hot concentrated solution of potassium hydroxide, dysmutation to the nearest stable oxidation degrees (-ii and + iv) is selenged. Make the equation of this OSR.
- Under the same conditions, sulfur is subjected to similar dumping, but excess of sulfur reacts with sulfite ions to form thiosulfate ions S 2 O 3 2. Make the equations of occurring reactions. ;
- Make the equation of electrolysis reactions a) copper nitrate solution with silver anode, b) lead nitrate solution with a copper anode.
a) CRCL 2 + FECL 3; b) CRSO 4 + FECL 3; c) CRSO 4 + H 2 SO 4 + O 2;
d) CRSO 4 + H 2 SO 4 + MNO 2; e) CRSO 4 + H 2 SO 4 + KMNO 4.
In which of these reactions, hydrogen peroxide is an oxidizing agent, and in what - a reducing agent?
| Experience 1. Oxidative properties of potassium permanganate in the acidic environment. K 3-4 drops of potassium permanganate solution Pour an equal amount of diluted sulfuric acid solution, and then a sodium sulfite solution to discoloration. Make a reaction equation. Experience 2.Oxidative properties of potassium permanganate in a neutral environment. To 3-4 drops of potassium permanganate solution, pour 5-6 drops of sodium sulfite solution. What substance was separated in the form of a sediment? Experience 3.. Oxidative properties of potassium permanganate in an alkaline environment. By 3-4 drops of potassium permanganate solution, pour 10 drops of a concentrated sodium hydroxide solution and 2 drops of sodium sulfite solution. The solution must acquire a green color. Experience 4.. Oxidative properties of potassium dichromate in the acidic environment. 6 drops of a solution of potassium dichromate acidify with four drops of dilute sulfuric acid solution and add sodium sulfite solution until the mixture color change. Experience 5. Oxidative properties of dilute sulfuric acid. In one test tube, put the zinc granule, and to another - a piece of copper tape. In both test tubes, add 8-10 drops of dilute sulfuric acid solution. Compare occurring phenomena. Experience to carry out in the exhaust cabinet! Experience 6. Oxidative properties of concentrated sulfuric acid. Similarly, experiment 5, but add a concentrated solution of sulfuric acid. After a minute, after the start of the release of gaseous reaction products, Introduce the filter paper strips in the tube, moistened with solutions of potassium permanganate and copper sulfate. Explain taking place. Experience to carry out in the exhaust cabinet! Experience 7. Oxidative properties of dilute nitric acid. Similarly, experiment 5, but add a diluted solution of nitric acid. Observe the change in the color of gaseous reaction products. Experience to carry out in the exhaust cabinet! Experience 8.. Oxidative properties of concentrated nitric acid. Put a piece of copper tape into the test tube and pour 10 drops of a concentrated solution of nitric acid. Carefully heat until metal dissolved. Experience to carry out in the exhaust cabinet! Experience 9.. Oxidative properties of potassium nitrite.To 5-6 drops of potassium nitrite solution pour equal volume of diluted sulfuric acid solution and 5 drops of potassium iodide solution. The formation of what substances is observed? Experience 10.. Recovery properties of potassium nitrite. By 5-6 drops of potassium permanganate solution add an equal amount of diluted sulfuric acid solution and potassium nitrite solution to complete bleaching of the mixture. Experience 11. Thermal decomposition of copper nitrate. One microfer of copper nitrate trihydrate is placed in a test tube, consolidate it in a tripod and carefully warm the open flame. Watch dehydration and subsequent decomposition of salt. Experience to carry out in the exhaust cabinet! Experience 12.. Thermal decomposition of lead nitrate. To conduct similarly to experience 11, placing lead nitrate in the test tube. Experience to carry out in the exhaust cabinet! What is the difference between the processes occurring during the decomposition of these salts? |
The propensity of organic compounds to oxidation is associated with the presence of multiple bonds, functional groups, hydrogen atoms with a carbon atom containing a functional group. The sequential oxidation of organic substances can be represented as the following chain of transformations:
Saturated hydrocarbon → Unsaturated hydrocarbon → Alcohol → Aldehyde (ketone) → Carboxylic acid → CO2 + H2O
The genetic relationship between classes of organic compounds seems to be here as a series of redox reactions that provide the transition from one class of organic compounds to another. Complete its products of complete oxidation (combustion) of any of the representatives of the classes of organic compounds. The dependence of the oxidation and reduction capacity of the organic matter on its structure: an increased tendency of organic compounds to oxidation is due to the presence in the molecule of substances: multiple connections (which is why alkenes, alkins, alkadiennes are so easily oxidized; Specific functional groups capable of easily oxidized (--sh, -oh (phenolic and alcohol), - NH2; activated alkyl groups located adjacent to multiple connections.
For example, propane can be oxidized to an unspecified aldehyde acherin oxygen in the presence of water vapor on bismuth-molybdenum catalysts.
H2CH-CH3 → H2CH-COH
As well as oxidation of toluene to benzoic acid permanganate potassium in an acidic environment. 5C6H5CH3 + 6KMNO4 + 9H2SO4 → 5C6H5COOH + 3K2SO4 + 6MNSO4 + 14H2O
the presence of hydrogen atoms with a carbon atom containing a functional group. An example is the reactivity in the reactions of oxidation of primary, secondary and tertiary alcohols for oxidation reactivity.
Despite the fact that during any oxidation reaction reactions occurs both oxidation and recovery, the reaction is classified depending on what is happening directly with the organic compound (if it is oxidized, they say about the oxidation process, if restored - about the recovery process) .
So, in the reaction of ethylene with permanganate potassium ethylene will be oxidized, and potassium permanganate is restored. The reaction is called ethylene oxidation.
When studying the comparative characteristics of inorganic and organic compounds, we acquainted using the degree of oxidation (C.O.) (in organic chemistry, especially carbon) and methods for its determination:
1) Calculation of Medium S.O. Carbon in the organic substance molecule: -8/3 +1 C3 H8 This approach is justified if all chemical bonds (burning, full decomposition) are destroyed during the reaction in the organic matter.
2) Definition of S.O. Each carbon atom:
In this case, the degree of oxidation of any carbon atom in the organic compound is equal to the algebraic sum of the numbers of all bonds with atoms of more electronegative elements, taken into account with the "+" sign at the carbon atom, and the number of bonds with hydrogen atoms (or other more electropositive element) taken into account with the sign "-" at the carbon atom. In this case, connections with neighboring carbon atoms are not taken into account. As the simplest example, we define the degree of carbon oxidation in the methanol molecule. The carbon atom is associated with three atoms of hydrogen (these relationships are taken into account with the sign "-"), one bond with an oxygen atom (it is taken into account with the "+" sign). We obtain: -3 + 1 \u003d -2. In order, the degree of carbon oxidation in methanol is -2. The calculated degree of carbon oxidation is, although the conditional value, but it indicates the nature of the electron density displacement in the molecule, and its change as a result of the reaction indicates a place of an oxidation-reducing process. We specify in what cases it is better to use one or another way.
The processes of oxidation, combustion, halogenation, nice, dehydrogenation, decomposition relate to redox processes. When moving from one class of organic compounds to another and increasing the degree of branching of the carbon skeleton of the compound molecules inside a separate class, the degree of oxidation of the carbon atom responsible for the restoring capacity of the compound is changed. Organic substances, in the molecules of which contain carbon atoms with maximum (- and +) values \u200b\u200bof CO (-4, -3, +2, +3), react complete oxidation-burning, but resistant to the effects of soft oxidizing agents and oxidizing agents . Substances in the molecules of which contain carbon atoms in CO -1; 0; +1, oxidized easily, the restoration abilities of them are close, the poet of their incomplete oxidation can be achieved at the expense of one of the famous oxidizing agents of small and medium power. These substances can show a dual nature, speaking and as an oxidizing agent, just as inherent inorganic substances.
Alkana
Alkenes
Oxidation processes depend on the structure of alkenet and the reaction medium.
1. In the oxidation of alkenes by the concentrated solution of potassium permanganate KMNO4 in an acidic medium (rigid oxidation), the σ- and π-bonds are ruined to form carboxylic acids, ketones and carbon oxide (IV). This reaction is used to determine the position of the double bond.
a) if the double bond is located at the end of the molecule (for example, at Bouthen-1), then one of the oxidation products is formic acid, easily oxidized to carbon dioxide and water:
b) if carbon atom contains two carbon substituents in the alkin molecule (for example, in a 2-methylbutene-2 \u200b\u200bmolecule), then when it is oxidized, the ketone formation occurs, since the conversion of such an atom into an atom of the carboxyl group is impossible without breaking C -C-Communication, relatively stable under these conditions:
c) if the alkene molecule is symmetrical and the double bond is contained in the middle of the molecule, then only one acid is formed during oxidation:
A feature of the oxidation of alkenes, in which carbon atoms at a double bond comprise two carbon radicals, is the formation of two ketones:
2. With neutral or weakly alkaline media, oxidation is accompanied by the formation of diols (ductomic alcohols), and the hydroxyl groups are joined by the carbon atoms, between which there was a double bond:
During this reaction, the purple color of the KMNO4 aqueous solution is discolored. Therefore, it is used as a high-quality reaction to alkenes (Wagner reaction).
3. The oxidation of alkenes in the presence of palladium salts (vacuker process) leads to the formation of aldehydes and ketones:
2ch2 \u003d CH2 + O2 PDCl2 / H2O → 2 CH3-CO-H
Homologists are oxidized to a less hydrogenated carbon atom: CH3-CH2-CH \u003d CH2 + 1 / 2O2 PDCL2 / H2O → CH3- CH2-CO-CH3 Alkina
The oxidation of acetylene and its homologues flows depending on which the process proceeds in which environment.
a) In the acidic environment, the oxidation process is accompanied by the formation of carboxylic acids:
1 The reaction is used to determine the structure of alkins on oxidation products:
2 In neutral and weakly alkaline media, the oxidation of acetylene is accompanied by the formation of appropriate oxalates (salts of oxalic acid), and the oxidation of homologues - the tip of the triple bond and the formation of carboxylic salts:
3 for acetylene:
1) In an acidic environment: H-C≡C-H KMNO4, H2SO4 → HOOC-COOH (sorval acid)
2) in neutral or alkaline environment: 3ch≡ch + 8kmnO4 H2O → 3kooc-Cook potassium oxalate + 8mnO2 ↓ + 2KOH + 2H2O
Arena (Benzene and His homologs)
In the oxidation of arena in an acidic medium, an acid formation should be expected, and in alkaline - salts. Gomezol homologs with one side chain (regardless of its length) are oxidized by a strong oxidizing agent to benzoic acid by α-carbon atom. Gomezol homologs are oxidized by potassium permanganate in a neutral medium to form potassium salts of aromatic acids.
5C6H5-CH3 + 6KMNO4 + 9H2SO4 \u003d 5C6H5COOH + 6MNSO4 + 3K2SO4 + 14H2O,
5C6H5-C2H5 + 12KMNO4 + 18H2SO4 \u003d 5C6H5COOH + 5CO2 + 12MNSO4 + 6K2SO4 + 28H2O,
C6H5-CH3 + 2KMNO4 \u003d C6H5COOK + 2MNO2 + KOH + H2O.
We emphasize that if there are several side chains in the molecule, then in an acidic medium, each of them is oxidized according to A-carbon atom to the carboxyl group, as a result of which polybent aromatic acids are formed:
1) in an acidic environment: C6H5-CH2-R KMNO4, H2SO4 → C6H5-COOH benzoic acid + CO2
2) In neutral or alkaline medium: C6H5-CH2-R KMNO4, H2O / (OH) → C6H5-COOK + CO2
3) oxidation of potassium permanganate homologs or potassium biocromate when heated: C6H5-CH2-R KMNO4, H2SO4, T˚C → C6H5-COOHBENZoICHICH + R-COOH
4) Cumol oxidation with oxygen in the presence of a catalyst (cumorole method for obtaining phenol): C6H5CH (CH3) 2 O2, H2SO4 → C6H5-OH phenol + CH3-CO-CH3 acetone
5C6H5CH (CH3) 2 + 18kmnO4 + 27H2SO4 → 5C6H5COOH + 42H2O + 18MNSO4 + 10CO2 + K2SO4
It should be paid to the fact that with the soft oxidation of styrene permanganate potassium KMNO4 in a neutral or weakly alkaline medium, the glaring of π-means communication occurs, glycol is formed (ductomic alcohol). As a result of the reaction, the painted solution of potassium permanganate is quickly discharged and a brown precipitate of manganese oxide (IV) falls. The oxidation of a strong oxidizing agent - potassium permanganate in an acidic medium - leads to a complete break of the double bond and the formation of carbon dioxide and benzoic acid, the solution is discolored.
C6H5-CH═CH2 + 2 KMNO4 + 3 H2SO4 → C6H5-COH + CO2 + K2SO4 + 2 MNSO4 +4 H2O
Alcohol
It should be remembered that:
1) Primary alcohols are oxidized to aldehydes: 3ch3-CH2OH + K2CR2O7 + 4H2SO4 \u003d 3CH3-CHO + K2SO4 + CR2 (SO4) 3 + 7H2O;
2) Secondary alcohols are oxidized to ketones:
3) For tertiary alcohols, the oxidation reaction is not characteristic. Tertiary alcohols, in the molecules of which there is no hydrogen atom with a carbon atom containing a group, it is not oxidized under normal conditions. In harsh conditions (under the action of strong oxidizing agents and at high temperatures), they can be oxidized to a mixture of low molecular weight carboxylic acids, i.e. The destruction of the carbon skeleton occurs. When the methanol is oxidized by the acidified solution of potassium permanganate or potassium dichromate, CO2 is formed. Primary alcohols during oxidation, depending on the conditions of the reaction, can form not only aldehydes, but also acids. For example, the oxidation of ethanol with dichromate potassium on cold ends with an acetic acid belt, and when heated - acetaldehyde:
3ch3-CH2OH + 2K2CR2O7 + 8H2SO4 \u003d 3CH3-COOH + 2K2SO4 + 2CR2 (SO4) 3 + 11H2O,
3CH3-CH2OH + K2CR2O7 + 4H2SO4
3CH3-CHO + K2SO4 + CR2 (SO4) 3 + 7H2O
I remember about the effect of the medium on the products of alcohol oxidation reactions, namely: a hot neutral solution of KMNO4 oxidizes methanol to potassium carbonate, and the remaining alcohols - to salts of the corresponding carboxylic acids:
Oxidation of glycolia
1,2 glycols are easily cleaved under mild conditions under the action of iodine acid. Depending on the structure of the original glycol, the oxidation products may be aldehydes or ketones:
If three or more HE-groups are associated with neighboring carbon atoms, then with the oxidation of iodine acid, medium or average atoms are converted into formic acid
The oxidation of glycols permanganate potassium in an acidic medium extends similarly to the oxidative splitting of alkenes and also leads to the formation of acids or ketones depending on the structure of the original glycol.
Aldehydes and Ketones
Aldehydes are easier than alcohols, oxidized into the appropriate carboxylic acids not only under the action of strong oxidizing agents (air oxygen, acidified solutions KMNO4 and K2Cr2O7), but also under the action of weak (ammonia solution of silver oxide or copper hydroxide (II)):
5ch3-cho + 2kmnO4 + 3H2SO4 \u003d 5CH3-COOH + 2MNSO4 + K2SO4 + 3H2O,
3ch3-cho + K2Cr2O7 + 4H2SO4 \u003d 3CH3-COOH + CR2 (SO4) 3 + K2SO4 + 4H2O,
CH3-CHO + 2OH CH3-COONH4 + 2AG + 3NH3 + H2O
Special attention!!! The oxidation of methanal with ammonium solution of silver oxide leads to the formation of ammonium carbonate, and not formic acid: HChO + 4OH \u003d (NH4) 2CO3 + 4AG + 6NH3 + 2H2O.
4.5.B. Oxidative splitting of alkenes
In the oxidation of alkanes with an alkaline aqueous solution of potassium permanganate when heated or a solution of KMNO 4 in aqueous sulfuric acid, as well as during the oxidation of alkenes with chromium oxide solution (VI) CRO 3 in acetic acid or potassium dichroom and sulfuric acid, an initially formed glycol is subjected to oxidative degradation. The final result is the splitting of the carbon skeleton at the dual connection site and the formation as final products of ketones and (or) carboxylic acids depending on the substituents at double bond. If both carbon atoms at a double bond comprise only one alkyl group, the end product of the exhaustive oxidation will be a mixture of carboxylic acids, the alken's tetrazentized at double bond is oxidized to two ketones. Disament alkenes with terminal double bonds are split up to carboxylic acid and carbon dioxide.
Due to the low yields of carboxylic acids and ketones, the reaction of an exhaustive oxidation of alkenes in the classic version was not widely used and previously used, mainly to establish the structure of the original alkenet by destructive oxidation products. Currently, the oxidation of alkenes (R-CH \u003d CH-R and R-CH \u003d CH 2) to carboxylic acids (RCOOH) with the help of permanganate or potassium dichromate is carried out under interfacial catalysis. The outputs of carboxylic acids are exceeded 90%.
4.5.V. Ozoneolysis Alkenov
The reaction of alkenes with ozone is the most important method of oxidative splitting of alkenes by dual communication. For many decades, this reaction served as the main method of determining the structure of the starting hydrocarbon, and also found the use of various carbonyl compounds in the synthesis. The ozone alkene reaction is carried out by passing the current of the ~ 5% mixture of ozone and oxygen into the alkene solution in the methylene chloride or ethyl acetate at -80 0 -100 0 C. The end of the reaction is controlled by a breakdown for free ozone with potassium iodide. The mechanism of this peculiar and complex reaction is mainly established thanks to the work of R Cryga. The first product of 1,3-dipolar cycloprication to double bond is the so-called Molozonide (1,2,3-trioxolane). This adduct is unstable and further spontaneously decomposes with the disclosure of the cycle and the formation as a final product of normal ozonide (1,2,4-trioxolane).
Currently, it is generally recognized that the conversion of the Molozonide into ordinary ozonide occurs by the mechanism of splitting - recombination. Molozonide undergoes spontaneous disclosure of an unstable 1,2,3-trioxolane cycle to form a carbonyl compound and bipolar ion, which further react among themselves according to the scheme of 1,3-dipolar cycloprication.
The reduced diagram of the regrouping of the Molosonide into normal ozonid is confirmed by the fact that if the other carbonyl compound is present to the complete formation of ozonide in the reaction mixture as a "interceptor" of the bipolar ion, the other carbonyl compound is formed, the so-called "mixed ozonide" is formed. So, for example, under Ozonilize cis-Filbena in the presence of a benzaldehyde labeled by isotope 18 o, the label is part of the essential, not peroxidant bridge of Ozonida:
This result is in good agreement with the formation of mixed ozonide during the recombination of a bipolar ion with labeled benzaldehyde:
Ozonides are very unstable compounds that decompose with the explosion. They are not isolated individually, but split under the action of a wide variety of restructions. It should be distinguished by reducing and oxidative splitting. In the hydrolysis of ozonides, slowly split into carbonyl compounds and hydrogen peroxide. Hydrogen peroxide oxidizes aldehyde to carboxylic acids. This is the so-called oxidative decomposition of Ozonidov:
Thus, with oxidative decomposition of ozonides, carboxylic acids and (or) ketones are formed depending on the structure of the original alkin. As oxidizing agents, air oxygen, hydrogen peroxide, peaks or silver hydroxide can be used. Most often in synthetic practice, hydrogen peroxide in acetic or formic acid is used for this purpose, as well as hydrogen peroxide in the alkaline medium.
In practice, the method of oxidative decomposition of ozonides is used mainly to obtain carboxylic acids.
The restorative splitting of ozonidov is more important. Qink and acetic acid, triphenylphosphine or dimethyl sulfide are most common as reducing agents. In this case, aldehydes or ketones are endehydes or ketones depending on the structure of the initial alkene.
From the above examples, it can be seen that the tetrazent-substituted alkane during ozoneism and the subsequent recovery decomposition of Ozonida forms two ketones, while the tris-substituted alkene gives ketone and aldehyde. Disubstituted symmetric alkene during ozoneolysis forms two aldehydes, and alkenes with terminal bond - aldehyde and formaldehyde.
An interesting modification of ozonelysis is the method where sodium borohydride is used as a reducing agent of ozonide, in this case the final reaction products are primary or secondary alcohols formed during the restoration of the aldehydes and kestons.
Ozoneolysis of alkenes is a complex, time-consuming and explosive process that requires the use of special equipment. For this reason, other methods of oxidative splitting of alkenes have been developed to carbonyl compounds and carboxylic acids, which successfully replace the ozonolysis reaction in synthetic practice.
One of the modern preparative methods of oxidative destruction of alkenes was proposed in 1955 R. Lemier. The basis of this method is the hydroxylation of alkenes using potassium permanganate, followed by the splitting of the vicinal glycol with a sodium period of Naio 4 at a pH of ~ 7 8. Periodate itself does not interact with alkene. Products of this two-stage oxidative splitting are ketones or carboxylic acids, since the aldehydes under these conditions are also oxidized to carboxylic acids. In the Lemier method, the problem of separation of one of the reaction products does not arise, - manganese dioxide, as well as dioxide, and manganate are again oxidized to the periodate to Permanganate ion. This allows you to use only catalytic quantities of potassium permanganate. Below are some typical examples of the oxidative splitting of alkenes by the lemier method.
Citronelol - alcohol, part of rose oil, geranium oil and lemon, is oxidized by a mixture of potassium periodant and sodium periodate in aqueous acetone at 5 10 0 c to 6-hydroxy-4-methyl gexanecarboxylic acid with quantitative output.
In another variety of this method, instead of potassium permanganate, the catalytic amounts of osmia tetraoxide are used (LEMIDE, Johnson 1956). The special advantage of the combination of OSO 4 and Naio 4 is that it allows you to stop the oxidation at the aldehyde stage. Osmia tetraoxide is joined by a double alkene bond with the formation of an osmat, which is oxidized by a sodium period of to carbonyl compounds with the regeneration of the four-fold osmium.
Instead of tetraoxide, Osmia can also use the RUO 4 tetraoxide. The oxidative destruction of alkenes by LEMIDE-Johnson leads to the same products as ozoneolysis with the reducing splitting of Ozonidov.
In terms of modern organic chemistry, it means that the combination of OSO 4 -NaIO 4 is synthetic equivalent The reactions of ozonolysis of alkenes followed by reducing splitting. Similarly, the oxidation of alkens with a mixture of permanganate and periodate is a synthetic equivalent of ozonolysis with oxidative decomposition of ozonidis.
Thus, the oxidation of alkenes is not only a combination of preparative methods for obtaining alcohols, epoxides, diols, aldehydes, ketones and carboxylic acids, it is also one of the possible ways to establish the structure of the original alkene. Thus, according to the result, the oxidative destruction of alkenes can determine the position of the double bond in the molecule, while the stereochemical result syn- or anti-alkena hydroxylation allows us to conclude its geometry.
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