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Obtaining benzaldehyde from benzene. Benzaldehyde - a change in legislation and how to buy it now




Nomenclature. Aromatic aldehydes are usually named according to rational nomenclature:

Properties. Most aromatic aldehydes are liquids that are poorly soluble in water. If the aldehyde group is attached directly to the aromatic ring, then the aldehydes have a pleasant smell; aldehydes in which the aldehyde group is in the side chain (for example, phenylacetic aldehyde) have a pungent odor.

Aromatic aldehydes, in which the aldehyde group is attached to the aromatic ring, enter into. a number of chemical reactions characteristic of fatty aldehydes: the formation of a silver mirror, oxidation with atmospheric oxygen, at? a compound of hydrocyanic acid, sodium bisulfite, etc. In addition, they also exhibit some specific reactions. These reactions may include:

Cannizzaro reaction. This reaction, discovered by the Italian scientist Cannizzaro, consists in the fact that in the presence of a concentrated alkali solution of two benzaldehyde molecules, one is reduced to form benzyl alcohol, while the other is oxidized to benzoic acid. The reaction proceeds as follows:

benzoin condensation. Two molecules of benzaldehyde under the catalytic action of potassium cyanide

enter into a condensation reaction with the formation of the so-called benzoin

The action of chlorine. Under the action of chlorine on aromatic aldehydes (for example, on benzaldehyde), the hydrogen atom of the aldehyde group is replaced by chlorine with the formation of acid chlorine anhydride:

Ways to receive. Aromatic aldehydes can be obtained by all methods of obtaining fatty aldehydes (oxidation of the corresponding alcohols, reduction of acids, anhydride chlorides, etc.).

To obtain aromatic aldehydes such as benzaldehyde, specific methods are used, for example, the oxidation of benzene homologues:

Benzoic aldehyde (benzaldehyde):

Under normal conditions, it is a colorless liquid with a temp. bale 179°C, with a strong smell of bitter almonds.

Benzaldehyde in the form of cyanohydrin is part of the amygdalin glycoside, which is found in bitter almonds, leaves of bird cherry, laurel cherry, etc. During the hydrolysis of amygdalin, benzaldehyde and hydrocyanic acid are released.

Benzaldehyde is used as a starting or intermediate substance for the synthesis of dyes and various organic compounds. Benzaldehyde and its derivatives are used for the synthesis of aromatic substances.


Benzaldehyde (benzoic aldehyde) - BENZALDEHYDE (CAS No. 100-52-7), TNVED code: 2912210000

  • the simplest aromatic aldehyde with the chemical formula C 6 H 5 CHO;
  • colorless liquid that turns yellow during storage with the smell of bitter almonds;
  • rapidly oxidized to benzoic acid;
  • toxic, when working with it you need to use personal protective equipment;
  • combustible liquid. Boiling point 179 °С, flash point 64 °С, self-ignition temperature 205 °С;
  • a precursor whose circulation in the Russian Federation is limited and for which special control measures are established.

Who uses benzaldehyde and why

  • precursor for other organic reagents, for example, for the synthesis of mandelic acid:

  • raw materials for the synthesis of other aromatic substances (acetals of benzaldehyde, cinnamic aldehyde, cinnamic acid, benzyl benzoate, jasminaldehyde, hexylcinnamic aldehyde), as well as triphenylmethane and other dyes;
  • in perfumery and cosmetic compositions. Benzaldehyde - a fragrant substance in perfumery (threshold concentration 2.61 * 10 -8 g / l);
  • as a food flavoring. In its production, it is used by chemical-food plants as a component of food essences;
  • as a solvent;
  • in the production of various medicines, including essential drugs (essential medicines).

Changes in legislation and resulting problems in the acquisition of benzaldehyde

Until recently, namely until April 21, 2015, any legal entity, having received permission from the Ministry of Industry and Trade, could import and sell benzaldehyde, which belonged to the II list of the IV List of precursors. At present, with the adoption of Decree of the Government of the Russian Federation of April 9, 2015 N 328, benzaldehyde has moved from the II list of precursors in accordance with the Decree of the Government of the Russian Federation of June 30, 1998 N 681 “On approval of the list of narcotic drugs, psychotropic substances and their precursors subject to control in of the Russian Federation" in List I of IV of the List of Precursors, the turnover of which in the Russian Federation is limited and in respect of which special control measures are established.

Being in List I of IV of the List of precursors, the circulation of which in the Russian Federation is limited and for which control measures are established in accordance with the legislation of the Russian Federation and international treaties of the Russian Federation, significantly complicates the process of purchasing and importing benzoic aldehyde. Benzaldehyde is not produced in Russia, and it has to be purchased abroad (China, America, Europe), the import of which is now restricted by law. After moving to the 1st list, benzaldehyde can only be purchased by “state unitary enterprises that have an appropriate license for the circulation of narcotic drugs, psychotropic substances and their precursors, the cultivation of narcotic plants” (quote from the Decree of the Government of the Russian Federation No. 181 dated March 21, 2011 "On the procedure for the import into the Russian Federation and export from the Russian Federation of narcotic drugs, psychotropic substances and their precursors"). That is, if earlier there were no big problems with the acquisition of this very important substance in the chemical industry, now they will appear. Unitary enterprises (FGUP) for its import will be forced to obtain two, it should be noted, expensive licenses, namely a license from the Federal Drug Control Service worth about 90,000 rubles and a license from the Ministry of Industry and Trade (its cost is about 95,000 rubles). It should be noted that these licenses are issued only for 1 year, they do not depend on the amount of benzaldehyde purchased by the enterprise. They are issued to a specific supplier of benzaldehyde, that is, you do not have the opportunity to change the supplier if you are not satisfied with the quality, and you have no legal opportunity to check the quality, since you will not be able to receive a sample due to the fact that this is a group I precursor, it turnover is limited even in the smallest sample sizes.

In addition, if legal entities and individual entrepreneurs plan to carry out activities for the circulation of benzaldehyde, they need to obtain the conclusion of the Federal Drug Control Service of Russia and a license from Roszdravnadzor for the circulation of precursors of narcotic drugs and psychotropic substances included in List I of List IV.

Thus, the cost of benzaldehyde for the end user can increase several times. Today in Russia there are great difficulties with the purchase of benzaldehyde. Those enterprises that consume it in small quantities will be especially hard hit.

Author's note

So, changes in legislation give rise to a number of problems with the purchase of benzaldehyde:

  1. Obtaining expensive licenses for the import and circulation of benzaldehyde
  2. Import of benzaldehyde only for unitary enterprises (now only Federal State Unitary Enterprises can import benzaldehyde into Russia)
  3. Inability to check the quality of benzaldehyde at the manufacturer (it is practically impossible to import and test a sample, since the import of even a small sample requires the execution of all permits, obtaining expensive licenses, and this is not economically feasible)

Question - Where to buy benzaldehyde?

Answer - you can buy benzaldehyde from FSUE SKTB Tekhnolog

FSUE SKTB Tekhnolog uses benzaldehyde in the production of pharmaceutical substances. Therefore, FSUE SKTB Tekhnolog is forced to regularly purchase benzaldehyde in fairly large quantities. In this regard, we are currently issuing licenses for the import of benzaldehyde into Russia and for its circulation. So we have the opportunity to sell it to other organizations (having a license for the circulation of such substances). If you use benzaldehyde in your production or you have a license for circulation, please contact us regarding the purchase. We are ready to offer you good prices. To plan supplies, on the purchase of benzaldehyde, please contact the commercial department of our company at the numbers listed on the page "

Benzoic aldehyde is formed in many reactions: during the oxidation of benzyl alcohol C 6 H 5 -CH 2 OH, during the reduction of benzoic acid with sodium amalgam, during dry distillation of a mixture of calcium salts of benzoic and formic acids, during boiling of benzyl chloride C 6 H 5 -CH 3 Cl with water and nitrogen-lead salt, when heated with water to 150-160 ° benzylidene chloride C 6 H 5 -CHCl 2 . The last two reactions are used in the industrial synthesis of benzaldehyde. Currently, there are many ways to obtain benzaldehyde. The main ones are considered to be chlorination and oxidation of toluene. Methods such as partial oxidation of benzyl alcohol, alkyl hydrolysis of benzal chloride, benzene carbonylation, and fermentation have also been developed. Benzaldehyde can be synthesized from cinnamaldehyde obtained from cinnamon oil by boiling in an aqueous/alcoholic solution at 90°C - 150°C in the presence of alkaline components (usually sodium carbonate or bicarbonate) for 5 - 80 hours, followed by distillation of the resulting benzaldehyde.

Industrial methods for obtaining benzaldehyde:

1. Fermentation of natural raw materials (the enzyme emulsin is already contained in the seeds)

The pits of almonds, apricots, apples and cherries contain significant amounts of amygdalin. This glycoside, under the action of the enzyme, is converted into benzaldehyde, hydrocyanic acid and two glucose molecules. Benzaldehyde is formed by the breakdown of amygdalin glucoside under the influence of the emulsin enzyme. This method for obtaining benzaldehyde from various parts of plants containing amygdalin (peach, apricot, apple, bitter almonds, laurel leaves) is based on the reaction of Liebig and Wöhler. For this purpose, bitter almonds are preliminarily pressed under a press to remove fatty oil, the pomace is boiled with water for about half an hour and allowed to cool; then a new amount of bitter almonds, infused in cold water, is added to the resulting mass, everything is left to stand for 12 hours and then distilled. Thus, up to 2% benzoic aldehyde (by weight) is obtained from the pomace. Commercially available peach pits, already stripped of their fatty oil content, can be used to produce benzoic aldehyde in the same way. Since during the breakdown of amygdalin under the influence of emulsin, along with benzoic aldehyde, glucose and hydrocyanic acid are formed - C 20 H 27 NO 11 + 2H 2 O \u003d C 7 H 6 O + HCN + 2C 6 H 12 O 6, the process of obtaining benzaldehyde from plant products is necessary be carried out with great care - the receiver must be hermetically connected to the refrigerator tube, and non-condensed volatile products should be carefully removed from the working room to the outside. Then you need to precipitate water-insoluble iron hexacyanoferrate with soluble iron salts, and distill benzaldehyde from the resulting mixture.

benzoic aldehyde (benzaldehyde) C 6 H 5 CHO - the simplest aromatic aldehyde, molecular weight 106.12, colorless liquid with a characteristic smell of bitter almonds or apple pits, turning yellow during storage and oxidizing with atmospheric oxygen to benzoyl peroxide (explosive), later turning into benzoic acid.

Story

Physical properties

So pl. −26 degrees Celsius, T.bp. 179 degrees Celsius. Soluble in ethanol, ether and other organic solvents.

Benzaldehyde is rapidly oxidized in air to benzoic acid. Heating in the presence of KCN results in benzoin:

  • 2C 6 H 5 CHO \u003d C 6 H 5 CH (OH) COC 6 H 5.

Benzaldehyde is able to enter into electrophilic substitution reactions, and it reacts selectively, forming meta-substituted products.

Receipt

From natural raw materials

Bitter almond kernels contain the glycoside amygdalin. In a slightly smaller amount, it is present in the stones of apricots, peaches, cherries, sweet cherries, and other stone fruits. You can tell if your bones contain amygdalin by smelling like benzaldehyde.

  • C 6 H 5 CH (CN) O-C 12 H 21 O 10 (amygdalin glycoside) + enzymatic hydrolysis (enzymes are already contained in the seeds themselves) = C 6 H 5 CHO + HCN + sugar.

Further, water-insoluble iron hexacyanoferrate precipitates with soluble iron salts and benzaldehyde is distilled off with steam.

From toluene

  • C 7 H 8 + Cl 2 + light \u003d C 6 H 5 CHCl 2 (benzal chloride) + hydrolysis of H 2 O (cat. Fe powder, Fe benzoate) \u003d (yield 76%) C 6 H 5 CHO
  • C 7 H 8 + MnO 2 + H 2 SO 4 65% (t40°C) = C 6 H 5 CHO
  • C 7 H 8 + 2CrO 2 Cl 2 (chromyl chloride) (in carbon disulfide, carbon tetrachloride) (t25-45 ° C) = precipitate C 6 H 5 CH 3 * (CrO 2 Cl 2) 2 + H 2 O = C 6 H 5 CHO (yield 70-80%)
  • C 7 H 8 + CrO 3 + (CH 3 CO) 2 O + CH 3 COOH (t5-10 ° C) \u003d C 6 H 5 CH (OOCCH 3) 2 + HCl (hydrolysis) \u003d C 6 H 5 CHO

C 7 H 8 + air + cat. V 2 O 5 ; 350-500°С = C 6 H 5 CHO

From benzyl halides

  • C 6 H 5 CH 2 Cl + Pb(NO 3) 2 aq.; HNO 3 dil.; 100 ° С \u003d C 6 H 5 CH 2 ONO 2 + NaOH \u003d C 6 H 5 CHO
  • C 6 H 5 CH 2 Cl + C 6 H 12 N 4 (urotropine) (in boiling 60% C 2 H 5 OH or in 50% CH 3 COOH) = C 6 H 5 CHO
  • C 6 H 5 CH 2 Cl + C 5 H 5 N (pyridine) \u003d Cl- + n-ONC 6 H 4 N (CH 3) 2 (p-nitrosodimethylaniline) \u003d C 6 H 5 CH \u003d N + (O-) C 6 H 4 N (CH 3) 2 + H 2 O (H +) \u003d C 6 H 5 CHO
  • C6H5CH2Cl + (CH 3) 2 C \u003d N + (ONa) O- (sodium derivative of 2-nitropropane) \u003d (CH 3) 2 C \u003d NOH + NaCl + C 6 H 5 CHO (yield 68-73%)

Direct formylation of benzene and its homologues

  • C 6 H 6 + CO + HCl + catalyst (AlCl 3 + CuCl) = n-CH 3 C 6 H 4 CHO (yield 50-55%) - Gattermann-Koch reaction
  • HCOOCH 3 + PCl 5 \u003d CHCl 2 OCH 3 (dichloromethyl methyl ether) + POCl3

C 6 H 6 + CHCl 2 OCH 3 (dichloromethyl methyl ether) + catalyst (AlCl 3, TiCl 4, SnCl 4) in CH 2 Cl 2 or CS 2, 0 ° C = C 6 H 5 CHO

  • (C 6 H 5 CH 3 + NaCN + AlCl 3 + HCl at 100 ° C = n-CH 3 C 6 H 4 CHO (yield 39%), (yield of unsubstituted benzaldehyde from benzene 11-39%)
  • C 6 H 5 OCH 3 (anisole) + NaCN + AlCl 3 + HCl at 40-45 ° C \u003d CH 3 OC 6 H 4 CHO (anisaldehyde, almost quantitative yield), (the reaction works well on phenols and their esters)
  • HCON(CH3)2(dimethylformamide) + POCl3 (exothermic reaction) + ArH = ArCH(OPOCl2)(N+H(CH3)2Cl-) + H2O = ArCHO + NH(CH3)2 + H3PO4

From acid chlorides, esters, nitriles, alcohols, phenols

  • ArCOCl(acid chloride) + C6H5NH2(aniline) = ArCO-NHC6H5(anilide) + PCl5 = ArCCl=NC6H5(imino chloride) + SnCl2(anhydrous) = ArCH=NC6H5(anil) + H2O = C6H5NH2 + ArCOH (isolation of intermediates optional) ( yield 62%)
  • ArCOOC2H5(ester) + NH2-NH2(hydrazine) = ArCO-NHNH2(hydrazide) + C6H5SO2Cl(benzenesulfonic chloride) = ArCO-NHNH-SO2C6H5 + KOH = ArCOH + N2 + C6H5SO2OK (40-85% yields)
  • C 6 H 5 CN + SnCl 2 (anhydrous) + HCl (in

Benzaldehyde (C 7 H 6 O) is a common aromatic aldehyde found in bitter almond oil.

For the first time, it was discovered as a result of isolation from bitter essential oils - in 1803 it was discovered by the French pharmacist Metre, and Wöhler and Liebig carried out the first synthesis of benzaldehyde in 1832. Benzaldehyde is a colorless (or slightly yellow) liquid that is immiscible with water. Because of the aroma and taste of almonds, it is used, among other things, in perfumery and cosmetic compositions, and as a food flavoring where it is necessary to imitate almonds.

The main method of industrial production is either chlorination of toluene to benzyl chloride, followed by oxidation in an aqueous medium (the reaction is shown in the picture below), or chlorination of the same toluene to benzal chloride (dichloromethylbenzene) and its hydrolysis.

In the laboratory, benzaldehyde can be obtained by oxidizing benzyl alcohol or by retroaldol condensation of cinnamic aldehyde (the latter process is more likely to form benzaldehyde as a by-product). The starting material for the biosynthesis of benzaldehyde is the amino acid phenylalanine.

In almonds, apricot and peach pits, and apple kernels, benzaldehyde forms a glycoside known as amidgalin.

Enzymatic cleavage of amidgalin in the intestine leads to its destruction with the formation of benzaldehyde, glucose and hydrogen cyanide (hydrocyanic acid in aqueous solution). , in principle, under certain conditions, the decomposition products of amidgalian can be poisoned (even fatally - in the 1980-90s, at the level of rumors or even in newspapers, cases of cyanide poisoning with alcohol tinctures on stone fruits were described, from which, when preparing the tincture, someone was too lazy to remove these bones ). The pulp of peaches, plums, apricots and apples does not contain amidgalin, so the pulp of these fruits cannot be a source of cyanide. Note that the plants themselves accumulate amidgalin in the seeds precisely as a means of poisoning the one who eats them, but not a person, but various kinds of codling insects, which need much less cyanide before death (well, you can compare the mass of a person and the mass of a plum codling moth and evaluate , how many times less cyanide will be required for the codling moth.The estimate will still be rough, since the metabolism of an insect and a person differ). Increasing the sugar content in a tincture or, say, in different varieties of almonds reduces the risk of hydrogen cyanide poisoning, which interacts with carbohydrates, lowering its concentration. Benzaldehyde, which is used much more often than hydrocyanic acid in cooking (rare cases of the use of HCN and its salts as additives for tea and coffee can be found, for example, in the novels of A. Christie), is less dangerous - lethal for the average (80 kg ) a dose of one-time consumption is considered to be 50 grams, despite the fact that for table salt the same value is less - about 40 grams.

Benzaldehyde is an organic substance with rich chemical properties, combining the properties of carbonyl compounds and benzene derivatives. It can be oxidized to benzoic acid, reduced to benzyl alcohol. Benzaldehyde reacts with aldol condensation with acetaldehyde to form cinnamic aldehyde.

Benzaldehyde is also characterized by a redox disproportionation reaction occurring under conditions of basic catalysis (Canizzaro reaction). The products of this reaction are benzyl alcohol and benzoic acid: