Editing Ethylene glycol (section)

== Uses ==
===Coolant and heat-transfer agent===
A major use of ethylene glycol is as an antifreeze agent in [[coolant]]s. This can be useful for automobiles and [[air-conditioning]] systems that either have external [[chiller]]s or [[Air handler|air handlers]], or must cool below the freezing temperature of water. In [[geothermal heating]]/cooling systems, ethylene glycol is the [[fluid]] that transports heat through the use of a [[geothermal heat pump]].  The ethylene glycol either gains energy from the source (lake, ocean, [[water well]]) or dissipates heat to the sink, depending on whether the system is being used for heating or cooling.

Pure ethylene glycol has a [[specific heat capacity]] about one half that of water.  So, while providing freeze protection and an increased boiling point, ethylene glycol lowers the specific heat capacity of water mixtures relative to pure water.  A 1:1 mix by mass has a specific heat capacity of about 3140 J/(kg·°C) (0.75 BTU/(lb·°F)), three quarters that of pure water, thus requiring increased flow rates in same-system comparisons with water.

The mixture of ethylene glycol with water provides additional benefits to coolant and antifreeze solutions, such as preventing corrosion and acid degradation, as well as inhibiting the growth of most microbes and fungi.<ref>{{Cite web|url=http://www.hydratechglobal.net/technical/Ethylene+Glycol/58/en|title=Hydratech - Specialist Fluid Solutions|website=www.hydratechglobal.net|access-date=2020-02-24|archive-date=2021-05-14|archive-url=https://web.archive.org/web/20210514041855/http://www.hydratechglobal.net/technical/Ethylene+Glycol/58/en|url-status=dead}}</ref> Mixtures of ethylene glycol and water are sometimes informally referred to in industry as glycol concentrates, compounds, mixtures, or solutions.

Table of thermal and physical properties of saturated liquid ethylene glycol:<ref>{{Cite book |last=Holman |first=Jack P. |title=Heat Transfer |publisher=McGraw-Hill Companies, Inc |year=2002 |isbn=9780072406559 |edition=9th |location=New York, NY |pages=600–606 |language=English}}</ref><ref>{{Cite book |author=Frank P. Incropera, David P. Dewitt, heodore L. Bergman, Adrienne S. Lavigne |title=Fundamentals of Heat and Mass Transfer |publisher=John Wiley and Sons, Inc. |year=2007 |isbn=9780471457282 |edition=6th |location=Hoboken, NJ |pages=941–950 |language=English}}</ref>
{|class="wikitable mw-collapsible"
!Temperature (°C)
!Density (kg/m<sup>3</sup>)
!Specific heat (kJ/(kg·K))
!Kinematic viscosity (m<sup>2</sup>/s)
!Conductivity (W/(m⋅K))
!Thermal diffusivity (m<sup>2</sup>/s)
!Prandtl number
!Thermal expansivity (K<sup>−1</sup>)
|-
|0
|1130.75
|2.294
|{{val|7.53E-5}}
|0.242
|{{val|9.34E-8}}
|615
|{{val|6.50E-4}}
|-
|20
|1116.65
|2.382
|{{val|1.92E-5}}
|0.249
|{{val|9.39E-8}}
|204
|{{val|6.50E-4}}
|-
|40
|1101.43
|2.474
|{{val|8.69E-6}}
|0.256
|{{val|9.39E-8}}
|93
|{{val|6.50E-4}}
|-
|60
|1087.66
|2.562
|{{val|4.75E-6}}
|0.26
|{{val|9.32E-8}}
|51
|{{val|6.50E-4}}
|-
|80
|1077.56
|2.65
|{{val|2.98E-6}}
|0.261
|{{val|9.21E-8}}
|32.4
|{{val|6.50E-4}}
|-
|100
|1058.5
|2.742
|{{val|2.03E-6}}
|0.263
|{{val|9.08E-8}}
|22.4
|{{val|6.50E-4}}
|}

===Anti-freeze===
Pure ethylene glycol freezes at about &minus;12&nbsp;°C (10.4&nbsp;°F) but, when mixed with water, the mixture freezes at a lower temperature. For example, a mixture of 60% ethylene glycol and 40% water freezes at &minus;45&nbsp;°C (&minus;49&nbsp;°F).<ref name=Ullmanns>{{Ullmann | author1 = Siegfried Rebsdat | author2 = Dieter Mayer | title = Ethylene Glycol | doi = 10.1002/14356007.a10_101}}</ref> [[Diethylene glycol]] behaves similarly. The freezing point depression of some mixtures can be explained as a [[colligative property]] of solutions but, in highly concentrated mixtures such as the example, deviations from ideal solution behavior are expected due to the influence of [[intermolecular forces]]. It's important to note that though pure and distilled water will have a greater specific heat capacity than any mixture of antifreeze and water, commercial antifreezes also typically contain an anti-corrosive additive to prevent pure water from corroding coolant passages in the engine block, cylinder head(s), water pump and radiator.

There is a difference in the mixing ratio, depending on whether it is ethylene glycol or propylene glycol. For ethylene glycol, the mixing ratios are typically 30/70 and 35/65, whereas the propylene glycol mixing ratios are typically 35/65 and 40/60. It is important that the mixture be frost-proof at the lowest operating temperature.<ref>{{Cite web|url=https://lcglad.dk/glycol/|title=Glycol til industri og erhverv|website=LC Glad|via=lcglad.dk|language=da|trans-title=Glycol for industry and business}}</ref>

Because of the depressed freezing temperatures, ethylene glycol is used as a [[de-icing]] fluid for [[windshield]]s and aircraft, as an [[antifreeze (coolant)|antifreeze]] in automobile engines, and as a component of [[Cryopreservation#Vitrification|vitrification]] (anticrystallization) mixtures for low-temperature preservation of biological tissues and organs.

The use of ethylene glycol not only depresses the freezing point of aqueous mixtures, but also elevates their boiling point. This results in the operating temperature range for heat-transfer fluids being broadened on both ends of the temperature scale. The increase in boiling temperature is due to pure ethylene glycol having a much higher boiling point and lower [[vapor pressure]] than pure water.

===Precursor to polymers===
[[File:PET.svg|thumb|upright|Ethylene glycol is one precursor to [[polyethyleneterephthalate]], which is produced on the multimillion ton scale annually.]]
In the [[plastics industry|plastic industry]], ethylene glycol is an important precursor to [[polyester]] fibers and [[resin]]s. [[Polyethylene terephthalate]], used to make [[plastic bottle]]s for [[soft drink]]s, is prepared from ethylene glycol.

===Other uses===
====Dehydrating agent====
Ethylene glycol is used in the natural gas industry to remove water vapor from natural gas before further processing, in much the same manner as [[triethylene glycol]] (TEG).

====Hydrate inhibition====
Because of its high boiling point and affinity for water, ethylene glycol is a useful [[desiccant]]. Ethylene glycol is widely used to inhibit the formation of [[Methane clathrate|natural gas clathrates]] (hydrates) in long multiphase pipelines that convey natural gas from remote gas fields to a gas processing facility. Ethylene glycol can be recovered from the natural gas and reused as an inhibitor after purification treatment that removes water and inorganic salts.

Natural gas is dehydrated by ethylene glycol. In this application, ethylene glycol flows down from the top of a tower and meets a rising mixture of water vapor and [[hydrocarbon]] gases. Dry gas exits from the top of the tower. The glycol and water are separated, and the glycol recycled. Instead of removing water, ethylene glycol can also be used to depress the temperature at which [[hydrate]]s are formed. The purity of glycol used for hydrate suppression (monoethylene glycol) is typically around 80%, whereas the purity of glycol used for dehydration (triethylene glycol) is typically 95 to more than 99%. Moreover, the injection rate for hydrate suppression is much lower than the circulation rate in a [[glycol dehydration]] tower.

====Precursor to other chemicals====
Minor uses of ethylene glycol include the manufacture of capacitors, as a chemical intermediate in the manufacture of [[1,4-Dioxane|1,4-dioxane]], as an additive to prevent [[corrosion]] in liquid cooling systems for [[personal computer]]s, and inside the lens devices of cathode-ray tube type of rear projection televisions. Ethylene glycol is also used in the manufacture of some [[vaccine]]s, but it is not itself present in these injections. It is used as a minor (1–2%) ingredient in [[shoe polish]] and also in some inks and dyes. Ethylene glycol has seen some use as a rot and fungal treatment for wood, both as a preventative and a treatment after the fact. It has been used in a few cases to treat partially rotted wooden objects to be displayed in museums. It is one of only a few treatments that are successful in dealing with rot in wooden boats, and is relatively cheap. Ethylene glycol may also be one of the minor ingredients in screen cleaning solutions, along with the main ingredient [[isopropyl alcohol]]. Ethylene glycol is commonly used as a [[preservative]] for biological specimens, especially in secondary schools during [[dissection]] as a safer alternative to [[formaldehyde]]. It is also used as part of the water-based hydraulic fluid used to control subsea oil and gas production equipment.

===Organic building block===
Although dwarfed by its use as a precursor to [[polyester]]s, ethylene glycol is useful in more specialized areas of organic chemistry.  

It serves as a [[protecting group]] in [[organic synthesis]] for manipulation of [[ketones]] and aldehydes.<ref>{{cite web | url = http://www.synarchive.com/protecting-group/Aldehyde_Ketone_Ethylene_glycol_acetal | title = Ethylene glycol acetal | website = The Organic Synthesis Archive | publisher = synarchive.com}}</ref><ref name  = greene>{{cite book | title = Protective Groups in Organic Synthesis | edition = Third |author1=Theodora W. Greene |author2=Peter G. M. Wuts | publisher = John Wiley & Sons | isbn = 978-0-471-16019-9 | pages = 312–322 | year = 1999}}</ref> By reacting with the carbonyl to form and acetal product, it reduces the likelihood of nucleophilic attack at that carbonyl carbon. After the desired reaction is completed, the carbonyl can be regenerated using acid-catalyzed hydrolysis. In one example, [[isophorone]] was protected using ethylene glycol:<ref>{{cite journal |author1=J. H. Babler |author2=N. C. Malek |author3=M. J. Coghlan | title = Selective hydrolysis of α,β- and β,γ-unsaturated ketals: method for deconjugation of β,β-disubstituted α,β-unsaturated ketones | year = 1978 | journal = [[J. Org. Chem.]] | volume = 43 | issue = 9 | pages = 1821–1823 | doi = 10.1021/jo00403a047}}</ref>
[[Image:Ethylene glycol protecting group.png|450px|center]]

The glycol-derived [[dioxalane]] of [[ethyl acetoacetate]] is a commercial fragrance [[fructone]].<ref>{{cite book |doi=10.1002/14356007.t11_t02 |chapter=Flavors and Fragrances, 3. Aromatic and Heterocyclic Compounds |title=Ullmann's Encyclopedia of Industrial Chemistry |date=2016 |last1=Panten |first1=Johannes |last2=Surburg |first2=Horst |pages=1–45 |isbn=978-3-527-30673-2 }}</ref>