Ethylene (according to IUPAC : ethene ) is an organic chemical compound described by the formula C 2 H 4 . It is the simplest alkene ( olefin ). Under normal conditions , a colorless combustible gas is lighter than air with a faint sweetish odor. Partially soluble in water (25.6 ml in 100 ml of water at 0 ° C), ethanol (359 ml under the same conditions). It is well soluble in diethyl ether and hydrocarbons.
| Ethylene | |
|---|---|
 | |
| Are common | |
| Chem. formula | C 2 H 4 |
| Physical properties | |
| Molar mass | 28.05 g / mol |
| Density | 0.001178 g / cm³ |
| Thermal properties | |
| T. melt. | −169.2 ° C |
| T. bale. | −103.7 ° C |
| T. aux. | 136.1 ° C |
| T. svpl. | 475.6 ° C |
| Classification | |
| Reg. CAS number | 74-85-1 |
| PubChem | |
| Reg. EINECS number | |
| Smiles | |
| Inchi | |
| RTECS | |
| Chebi | |
| ChemSpider | |
It contains a double bond and therefore refers to unsaturated or unsaturated hydrocarbons . It plays an extremely important role in industry, and is also a phytohormone . Ethylene is the most produced organic compound in the world [1] ; total global ethylene production in 2008 amounted to 113 million tons and continues to grow by 2-3% per year [2] . Ethylene has a narcotic effect. The hazard class is fourth [3] .
Content
Getting
Ethylene was widely used as a monomer before the Second World War due to the need to obtain high-quality insulating material that can replace polyvinyl chloride . After developing a method for the polymerization of ethylene under high pressure and studying the dielectric properties of the obtained polyethylene, production began first in the UK and later in other countries.
The main industrial method for producing ethylene is the pyrolysis of liquid petroleum distillates or lower saturated hydrocarbons. The reaction is carried out in tubular furnaces at + 800-950 ° C and a pressure of 0.3 MPa. When using straight-run gasoline as a raw material, the ethylene yield is approximately 30%. A significant amount of liquid hydrocarbons, including aromatic ones, is also formed simultaneously with ethylene. During gas oil pyrolysis, the ethylene yield is about 15-25%. The highest yield of ethylene - up to 50% - is achieved when saturated hydrocarbons are used as raw materials: ethane, propane and butane. Their pyrolysis is carried out in the presence of water vapor.
Upon release from production, during commodity-accounting operations, when checking it for compliance with regulatory and technical documentation, ethylene is sampled according to the procedure described in GOST 24975.0-89 “Ethylene and Propylene . Sampling methods. " Ethylene can be sampled either in gaseous or liquefied form in special samplers according to GOST 14921.
Ethylene industrially produced in Russia must comply with the requirements set forth in GOST 25070-2013 Ethylene. Technical conditions. "
Production Structure
Currently, 64% of the ethylene production structure falls on large-capacity pyrolysis plants, ~ 17% - on small-capacity gas pyrolysis plants, ~ 11% is gasoline pyrolysis and 8% falls on ethane pyrolysis.
Application
Ethylene is a leading product of basic organic synthesis and is used to produce the following compounds (listed in alphabetical order):
- Vinyl acetate ;
- Dichloroethane / vinyl chloride (3rd place, 12% of the total volume);
- Ethylene oxide (2nd place, 14-15% of the total volume);
- Polyethylene (1st place, up to 60% of the total volume);
- Styrene ;
- Acetic acid ;
- Ethylbenzene ;
- Ethylene glycol ;
- Ethyl alcohol .
Ethylene mixed with oxygen was used in medicine for anesthesia until the mid-1980s in the USSR and the Middle East. Ethylene is a phytohormone in almost all plants [4] , among other things [5] it is responsible for the falling of needles in conifers.
Electronic and spatial structure of a molecule
Carbon atoms are in the second valence state (sp 2 - hybridization ). As a result, three hybrid clouds form on the plane at an angle of 120 °, which form three σ-bonds with carbon and two hydrogen atoms; The p-electron, which did not participate in hybridization, forms a π-bond in the perpendicular plane with the p-electron of the neighboring carbon atom. This forms a double bond between carbon atoms. The molecule has a planar structure.
Basic chemical properties
Ethylene is a chemically active substance. Since there is a double bond between the carbon atoms in the molecule, one of them, less strong, breaks easily, and molecules attach, oxidize, and polymerize at the bond break point.
- Halogenation:
- Bromine water discoloration occurs. This is a qualitative response to unsaturated compounds.
- Hydrogenation:
- Hydrohalogenation:
- Hydration:
- This reaction was discovered by AM Butlerov , and it is used for the industrial production of ethanol.
- Oxidation:
- Ethylene is easily oxidized. If ethylene is passed through a solution of potassium permanganate, then it will discolor. This reaction is used to distinguish between limiting and unsaturated compounds. The result is ethylene glycol . Reaction equation [6] :
- Combustion:
- Polymerization (production of polyethylene ):
- Dimerization [7]
Biological role
Ethylene is the first gaseous plant hormone detected with a very wide range of biological effects [8] . Ethylene performs various functions in the life cycle of plants, including control of seedling development, ripening of fruits (in particular, fruits) [9] , bud opening (flowering process), aging and decay of leaves and flowers. Ethylene is also called the stress hormone, since it is involved in the response of plants to biotic and abiotic stress, and its synthesis in plant organs is enhanced in response to various kinds of damage. In addition, being a volatile gaseous substance, ethylene provides rapid communication between different organs of plants and between plants in a population, which is important. in particular, with the development of stress resistance [10] .
Among the most well-known functions of ethylene is the development of the so-called triple response in etiolated (grown in the dark) seedlings when treated with this hormone. The triple response includes three reactions: shortening and thickening of the hypocotyl, shortening of the root and strengthening of the apical hook (sharp bending of the upper part of the hypocotyl). The response of seedlings to ethylene is extremely important at the first stages of their development, as it promotes the penetration of sprouts to light [10] .
In the commercial gathering of fruits and fruits, special rooms or chambers are used to ripen the fruit , into the atmosphere of which ethylene is injected from special catalytic generators producing gaseous ethylene from liquid ethanol . Typically, a concentration of ethylene gas in the atmosphere of the chamber from 500 to 2000 ppm for 24-48 hours is used to stimulate fruit ripening. At a higher air temperature and a higher concentration of ethylene in the air, the ripening of the fruit is faster. However, it is important to control the carbon dioxide content in the chamber atmosphere, since high-temperature ripening (at temperatures above 20 degrees Celsius) or ripening at a high ethylene concentration in the chamber air leads to a sharp increase in the emission of carbon dioxide by rapidly ripening fruits, sometimes up to 10% carbon dioxide in the air after 24 hours from the start of ripening, which can lead to carbon dioxide poisoning of both workers harvesting ripened fruits and the fruits themselves [11] .
Ethylene was used to stimulate fruit ripening in ancient Egypt. The ancient Egyptians intentionally scratched or slightly wrinkled, beat off dates, figs and other fruits in order to stimulate their ripening (tissue damage stimulates the formation of ethylene by plant tissues). Ancient Chinese people burned wooden incense sticks or scented candles in closed rooms in order to stimulate the ripening of peaches (not only carbon dioxide, but also unoxidized intermediate combustion products, including ethylene, are released when candles or wood are burned). In 1864, it was discovered that the leakage of natural gas from street lamps causes inhibition of the growth of nearby plants in length, their twisting, anomalous thickening of stems and roots and accelerated ripening of fruits. [8] In 1901, Russian scientist Dmitry Nelyubov showed that the active component of natural gas causing these changes is not its main component, methane, but ethylene present in it in small quantities [12] . Later in 1917, Sarah Dubt proved that ethylene stimulates premature leaf fall [13] . However, it was not until 1934 that Gein discovered that the plants themselves synthesize endogenous ethylene. [14] . In 1935, Crocker suggested that ethylene is a plant hormone responsible for the physiological regulation of fruit ripening, as well as for the aging of vegetative tissues of plants, leaf decay and growth inhibition [15] .
Ethylene is formed in almost all parts of higher plants, including leaves, stems, roots, flowers, pulp and peel of fruits and seeds. Ethylene formation is regulated by many factors, including both internal factors (for example, the phase of plant development) and environmental factors. During the life cycle of a plant, the formation of ethylene is stimulated during such processes as fertilization (pollination), ripening of fruits, falling leaves and petals, aging and death of the plant. Ethylene formation is also stimulated by such external factors as mechanical damage or injury, attack of parasites (microorganisms, fungi, insects, etc.), external stresses and unfavorable development conditions, as well as by some endogenous and exogenous stimulants, such as auxins and others [16 ] .
The ethylene biosynthesis cycle begins with the conversion of the amino acid methionine to S-adenosylmethionine (SAMe) using the enzyme methionine adenosyltransferase. Then S-adenosyl-methionine is converted to 1-aminocyclopropane-1-carboxylic acid ( ACC ) using the enzyme 1-aminocyclopropane-1-carboxylate synthetase (ACC synthetase). The activity of ACC synthetase limits the speed of the entire cycle; therefore, the regulation of the activity of this enzyme is key in the regulation of ethylene biosynthesis in plants. The last stage of ethylene biosynthesis requires the presence of oxygen and occurs under the action of the aminocyclopropanecarboxylate oxidase (ACC oxidase) enzyme, formerly known as the ethylene forming enzyme. Ethylene biosynthesis in plants is induced by both exogenous and endogenous ethylene (positive feedback). The activity of ACC synthetase and, accordingly, the formation of ethylene increases also at high levels of auxins , especially indoleacetic acid, and cytokinins .
The ethylene signal in plants is perceived by at least five different families of transmembrane receptors, which are protein dimers . Known, in particular, the ethylene receptor ETR 1 in Arabidopsis ( Arabidopsis ). Genes encoding receptors for ethylene were cloned in Arabidopsis and then in tomato . Ethylene receptors are encoded by a variety of genes in both the Arabidopsis genome and the tomato genome. Mutations in any of the gene family, which consists of five types of ethylene receptors in Arabidopsis and a minimum of six types of receptors in tomato, can lead to insensitivity of plants to ethylene and impaired ripening, growth, and wilting processes [17] . DNA sequences characteristic of ethylene receptor genes have also been found in many other plant species. Moreover, an ethylene binding protein was found even in cyanobacteria [8] .
Unfavorable external factors, such as insufficient oxygen in the atmosphere, floods, droughts, frosts, mechanical damage (injury) to plants, attack of pathogenic microorganisms, fungi or insects, can cause increased formation of ethylene in plant tissues. So, for example, during a flood, the roots of the plant suffer from excess water and a lack of oxygen (hypoxia), which leads to the biosynthesis of 1-aminocyclopropane-1-carboxylic acid in them. ACC is then transported along pathways in the stems up to the leaves, and oxidized to ethylene in the leaves. The resulting ethylene promotes epinastic movements, leading to mechanical shaking of water from the leaves, as well as withering and falling of leaves, flower petals and fruits, which allows the plant to simultaneously get rid of excess water in the body and reduce the need for oxygen by reducing the total mass of tissues [ 18] .
Small amounts of endogenous ethylene are also formed in animal cells, including humans, during lipid peroxidation. A certain amount of endogenous ethylene is then oxidized to ethylene oxide , which has the ability to alkylate DNA and proteins , including hemoglobin (forming a specific adduct with N-terminal hemoglobin valine - N-hydroxyethyl-valine) [19] . Endogenous ethylene oxide can also alkylate the guanine bases of DNA, which leads to the formation of the adduct of 7- (2-hydroxyethyl) -guanine, and is one of the reasons for the risk of endogenous carcinogenesis inherent in all living beings [20] . Endogenous ethylene oxide is also a mutagen [21] [22] . On the other hand, there is a hypothesis that if it were not for the formation in the body of small amounts of endogenous ethylene and, accordingly, ethylene oxide, then the rate of occurrence of spontaneous mutations and, accordingly, the rate of evolution would be much lower.
Notes
- ↑ Devanney Michael T. Ethylene (inaccessible link) . SRI Consulting (September 2009). Archived July 18, 2010.
- ↑ Ethylene ( inaccessible link) . WP Report . SRI Consulting (January 2010). Archived August 31, 2010.
- ↑ Gas chromatographic measurement of mass concentrations of hydrocarbons: methane, ethane, ethylene, propane, propylene, butane, alpha-butylene, isopentane in the air of the working area. Methodical instructions. MUK 4.1.1306-03 (Approved by the chief state sanitary doctor of the Russian Federation on March 30, 2003)
- ↑ "Growth and development of plants" V.V. Chub (Inaccessible link) . Date of treatment January 21, 2007. Archived January 20, 2007.
- ↑ "Delaying Christmas tree needle loss"
- ↑ Khomchenko G.P. §16.6. Ethylene and its homologues // Chemistry for applicants to universities. - 2nd ed. - M .: Higher School , 1993 .-- S. 345. - 447 p. - ISBN 5-06-002965-4 .
- ↑ W. Sh. Feldblyum. Dimerization and disproportionation of olefins. M .: Chemistry, 1978
- ↑ 1 2 3 Lin, Z .; Zhong, S .; Grierson, D. Recent advances in ethylene research // Journal of Experimental Botany : journal. - Oxford University Press , 2009. - Vol. 60 , no. 12 . - P. 3311–3336 . - DOI : 10.1093 / jxb / erp204 . - PMID 19567479 .
- ↑ Ethylene and Fruit Ripening / J Plant Growth Regul (2007) 26: 143-159 doi: 10.1007 / s00344-007-9002-y
- ↑ 1 2 Lutova L.A. Genetics of plant development / ed. S.G. Inge-Vechtomov. - 2nd ed .. - St. Petersburg: NL, 2010. - S. 432.
- ↑ External Link to More on Ethylene Gassing and Carbon Dioxide Control . ne-postharvest.com Archived September 14, 2010 on Wayback Machine
- ↑ Nelyubov D.N. On horizontal nutation in Pisum sativum and some other plants (Russian) // Transactions of the St. Petersburg Society of Natural History: Journal. - 1901. - T. 31 , No. 1 . , also Beihefte zum "Bot. Centralblatt ", T. X, 1901
- ↑ Doubt, Sarah L. The Response of Plants to Illuminating Gas (англ.) // Botanical Gazette : journal. — 1917. — Vol. 63 , no. 3 . — P. 209—224 . — DOI : 10.1086/332006 .
- ↑ Gane R. Production of ethylene by some fruits (англ.) // Nature. — 1934. — Vol. 134 , no. 3400 . — P. 1008 . — DOI : 10.1038/1341008a0 . — .
- ↑ Crocker W, Hitchcock AE, Zimmerman PW. (1935) «Similarities in the effects of ethlyene and the plant auxins». Contrib. Boyce Thompson Inst. 7. 231-48. Auxins Cytokinins IAA Growth substances, Ethylene
- ↑ Yang, SF, and Hoffman NE Ethylene biosynthesis and its regulation in higher plants (англ.) // Ann. Rev. Plant Physiol. : journal. - 1984. - Vol. 35 . — P. 155—189 . — DOI : 10.1146/annurev.pp.35.060184.001103 .
- ↑ Bleecker AB , Esch JJ , Hall AE , Rodríguez FI , Binder BM The ethylene-receptor family from Arabidopsis: structure and function. (англ.) // Philosophical transactions of the Royal Society of London. Series B, Biological sciences. - 1998. - Vol. 353, no. 1374 . — P. 1405—1412. — DOI : 10.1098/rstb.1998.0295 . — PMID 9800203 .
- ↑ Explaining Epinasty . planthormones.inf
- ↑ Filser JG, Denk B., Törnqvist M., Kessler W., Ehrenberg L. Pharmacokinetics of ethylene in man; body burden with ethylene oxide and hydroxyethylation of hemoglobin due to endogenous and environmental ethylene. (англ.) // Arch Toxicol. : journal. - 1992. - Vol. 66 , no. 3 . — P. 157—163 . — PMID 1303633 .
- ↑ Bolt HM, Leutbecher M., Golka K. A note on the physiological background of the ethylene oxide adduct 7-(2-hydroxyethyl)guanine in DNA from human blood. (англ.) // Arch Toxicol. : journal. - 1997. - Vol. 71 , no. 11 . — P. 719—721 . — PMID 9363847 .
- ↑ Csanády GA, Denk B., Pütz C., Kreuzer PE, Kessler W., Baur C., Gargas ML, Filser JG. A physiological toxicokinetic model for exogenous and endogenous ethylene and ethylene oxide in rat, mouse, and human: formation of 2-hydroxyethyl adducts with hemoglobin and DNA. (англ.) // Toxicol Appl Pharmacol. : journal. — 2000. — 15 May ( vol. 165 , no. 1 ). — P. 1—26 . — PMID 10814549 .
- ↑ Thier R., Bolt HM. Carcinogenicity and genotoxicity of ethylene oxide: new aspects and recent advances. (англ.) // Crit Rev Toxicol. : journal. — 2000. — September ( vol. 30 , no. 5 ). — P. 595—608 . — PMID 11055837 .
Literature
- Горбов А. И. ,. Этилен // Энциклопедический словарь Брокгауза и Ефрона : в 86 т. (82 т. и 4 доп.). - SPb. , 1890-1907.
- ГОСТ 24975.0-89 Этилен и пропилен. Методы отбора проб
- ГОСТ 25070-87 Этилен. Technical conditions
Links
- Безуглова О. С. Этилен . Удобрения и стимуляторы роста. Дата обращения 22 февраля 2015.