Orbital description of bonding between ethylene and a transition metal
Thishydrocarbon has fourhydrogenatoms bound to a pair ofcarbon atoms that are connected by adouble bond. All six atoms that comprise ethylene arecoplanar. The H-C-Hangle is 117.4°, close to the 120° for ideal sp²hybridized carbon. The molecule is also relatively weak: rotation about the C-C bond is a very low energy process that requires breaking theπ-bond by supplying heat at 50 °C.[citation needed]
Theπ-bond in the ethylene molecule is responsible for its useful reactivity. The double bond is a region of highelectron density, thus it is susceptible to attack byelectrophiles. Many reactions of ethylene are catalyzed by transition metals, which bind transiently to the ethylene using both the π and π* orbitals.[citation needed]
Being a simple molecule, ethylene is spectroscopically simple. Its UV-visspectrum is still used as a test of theoretical methods.[12]
Polyethylene production uses more than half of the world's ethylene supply. Polyethylene, also calledpolyethene andpolythene, is the world's most widely used plastic. It is primarily used to make films inpackaging,carrier bags and trashliners. Linearalpha-olefins, produced byoligomerization (formation of short-chain molecules) are used asprecursors,detergents,plasticisers,synthetic lubricants, additives, and also as co-monomers in the production of polyethylenes.[13]
Ethylene oxidation in the presence of a palladium catalyst can formacetaldehyde. This conversion remains a major industrial process (10M kg/y).[16] The process proceeds via the initial complexation of ethylene to a Pd(II) center.[citation needed]
Ethylene has long represented the major nonfermentative precursor toethanol. The original method entailed its conversion todiethyl sulfate, followed by hydrolysis. The main method practiced since the mid-1990s is the direct hydration of ethylene catalyzed bysolid acid catalysts:[18]
Ethylene isdimerized byhydrovinylation to given-butenes using processes licensed by Lummus orIFP. The Lummus process produces mixedn-butenes (primarily2-butenes) while the IFP process produces1-butene. 1-Butene is used as acomonomer in the production of certain kinds ofpolyethylene.[19]
Ethylene is a hormone that affects the ripening and flowering of many plants. It is widely used to control freshness inhorticulture andfruits.[20] The scrubbing of naturally occurring ethylene delays ripening.[21] Adsorption of ethylene by nets coated intitanium dioxide gel has also been shown to be effective.[22]
An example of a niche use is as ananesthetic agent (in an 85% ethylene/15% oxygen ratio).[23] It is also used as a refrigerant gas for low temperature applications under the name R-1150.[24]
Global ethylene production was 107 million tonnes in 2005,[9] 109 million tonnes in 2006,[25] 138 million tonnes in 2010, and 141 million tonnes in 2011.[26] By 2013, ethylene was produced by at least 117 companies in 32 countries. To meet the ever-increasing demand for ethylene, sharp increases in production facilities are added globally, particularly in theMideast and inChina.[27] Productionemits greenhouse gas, namely significant amounts of carbon dioxide.[28]
Ethylene is produced by several methods in thepetrochemical industry. A primary method issteam cracking (SC) where hydrocarbons and steam are heated to 750–950 °C. This process converts large hydrocarbons into smaller ones and introduces unsaturation. Whenethane is the feedstock, ethylene is the product. Ethylene is separated from the resulting mixture by repeatedcompression anddistillation.[17] In Europe and Asia, ethylene is obtained mainly from cracking naphtha, gasoil and condensates with the coproduction of propylene, C4 olefins and aromatics (pyrolysis gasoline).[29] Other procedures employed for the production of ethylene includeFischer-Tropsch synthesis andmethanol-to-olefins (MTO).[30]
Although of great value industrially, ethylene is rarely synthesized in the laboratory and is ordinarily purchased.[31] It can be produced via dehydration ofethanol withsulfuric acid or in the gas phase withaluminium oxide oractivated alumina.[32]
Some geologists and scholars believe that the famous Greek Oracle atDelphi (thePythia) went into her trance-like state as an effect of ethylene rising from ground faults.[36]
Ethylene appears to have been discovered byJohann Joachim Becher, who obtained it by heatingethanol with sulfuric acid;[37] he mentioned the gas in hisPhysica Subterranea (1669).[38]Joseph Priestley also mentions the gas in hisExperiments and observations relating to the various branches of natural philosophy: with a continuation of the observations on air (1779), where he reports thatJan Ingenhousz saw ethylene synthesized in the same way by a Mr. Enée in Amsterdam in 1777 and that Ingenhousz subsequently produced the gas himself.[39] The properties of ethylene were studied in 1795 by fourDutch chemists, Johann Rudolph Deimann, Adrien Paets van Troostwyck, Anthoni Lauwerenburgh and Nicolas Bondt, who found that it differed fromhydrogen gas and that it contained both carbon and hydrogen.[40] This group also discovered that ethylene could be combined withchlorine to produce theDutch oil,1,2-dichloroethane; this discovery gave ethylene the name used for it at that time,olefiant gas (oil-making gas.)[41] The term olefiant gas is in turn the etymological origin of the modern word "olefin", the class of hydrocarbons in which ethylene is the first member.[citation needed]
In the mid-19th century, the suffix-ene (an Ancient Greek root added to the end of female names meaning "daughter of") was widely used to refer to a molecule or part thereof that contained one fewer hydrogen atoms than the molecule being modified. Thus,ethylene (C 2H 4) was the "daughter ofethyl" (C 2H 5). The name ethylene was used in this sense as early as 1852.[42]
In 1866, theGerman chemistAugust Wilhelm von Hofmann proposed a system of hydrocarbon nomenclature in which the suffixes -ane, -ene, -ine, -one, and -une were used to denote the hydrocarbons with 0, 2, 4, 6, and 8 fewer hydrogens than their parentalkane.[43] In this system, ethylene becameethene. Hofmann's system eventually became the basis for the Geneva nomenclature approved by the International Congress of Chemists in 1892, which remains at the core of theIUPAC nomenclature. However, by that time, the name ethylene was deeply entrenched, and it remains in wide use today, especially in the chemical industry.
Following experimentation by Luckhardt, Crocker, and Carter at the University of Chicago,[44] ethylene was used as an anesthetic.[45][7] It remained in use through the 1940s, even while chloroform was being phased out. Its pungent odor and its explosive nature limit its use today.[46]
The 1979 IUPAC nomenclature rules made an exception for retaining the non-systematic nameethylene;[47] however, this decision was reversed in the 1993 rules,[48] and it remains unchanged in the newest 2013 recommendations,[49] so the IUPAC name is nowethene. In the IUPAC system, the nameethylene is reserved for thedivalent group -CH2CH2-. Hence, names likeethylene oxide andethylene dibromide are permitted, but the use of the nameethylene for the two-carbon alkene is not. Nevertheless, use of the nameethylene for H2C=CH2 (and propylene for H2C=CHCH3) is still prevalent among chemists in North America.[50]
"A key factor affecting petrochemicals life-cycle emissions is the methane intensity of feedstocks, especially in the production segment."[51] Emissions from cracking of naptha and natural gas (common in the US as gas is cheap there) depend a lot on the source of energy (for example gas burnt to provide high temperatures[52]) but that from naptha is certainly more per kg of feedstock.[53] Both steam cracking and production from natural gas via ethane are estimated to emit 1.8 to 2kg of CO2 per kg ethylene produced,[54] totalling over 260 million tonnes a year.[55] This is more than all other manufactured chemicals except cement and ammonia.[56] According to a 2022 report using renewable or nuclear energy could cut emissions by almost half.[53]
Like all hydrocarbons, ethylene is a combustibleasphyxiant. It is listed as anIARCgroup 3 agent, since there is no current evidence that it causes cancer in humans.[57]
^McAuliffe, C. (1966). "Solubility in Water of Paraffin, Cycloparaffin, Olefin, Acetylene, Cycloolefin, and Aromatic Hydrocarbons".Journal of Physical Chemistry.70 (4):1267–1275.doi:10.1021/j100876a049.
^abcNeiland, O. Ya. (1990)Органическая химия: Учебник для хим. спец. вузов. Moscow. Vysshaya Shkola. p. 128.
^Kestin J, Khalifa HE, Wakeham WA (1977). "The viscosity of five gaseous hydrocarbons".The Journal of Chemical Physics.66 (3):1132–1134.Bibcode:1977JChPh..66.1132K.doi:10.1063/1.434048.
^Elschenbroich C, Salzer A (2006).Organometallics: A Concise Introduction (2nd ed.). Weinheim: Wiley-VCH.ISBN978-3-527-28165-7.
^abcdKniel L, Winter O, Stork K (1980).Ethylene, keystone to the petrochemical industry. New York: M. Dekker.ISBN978-0-8247-6914-7.
^Kosaric N, Duvnjak Z, Farkas A, Sahm H, Bringer-Meyer S, Goebel O, Mayer D (2011). "Ethanol".Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. pp. 1–72.doi:10.1002/14356007.a09_587.pub2.ISBN9783527306732.
^Crimmins MT, Kim-Meade AS (2001). "Ethylene". In Paquette, L. (ed.).Encyclopedia of Reagents for Organic Synthesis. New York: Wiley.doi:10.1002/047084289X.re066.ISBN0471936235.
^Yang SF, Hoffman NE (1984). "Ethylene biosynthesis and its regulation in higher plants".Annu. Rev. Plant Physiol.35:155–89.doi:10.1146/annurev.pp.35.060184.001103.
