Ethers () are a class of organic compounds that contain an ether group — an oxygen atom connected to two alkyl or aryl groups — of general formula R–O–R'. A typical example is the solvent and anesthetic diethyl ether, commonly referred to simply as "ether" (CH₃-CH₂-O-CH₂-CH₃). Ethers are common in organic chemistry and pervasive in biochemistry, as they are common linkages in carbohydrates and lignin.

Structure and bonding

Ethers feature C-O-C linkage defined by a bond angle of about 110° and C-O distances of about 140 pm. The barrier to rotation about the C-O bonds is low. The bonding of oxygen in ethers, alcohols, and water is similar. In the language of valence bond theory, the hybridization at oxygen is sp³.

Oxygen is more electronegative than carbon, thus the hydrogens alpha to ethers are more acidic than in simple hydrocarbons. They are far less acidic than hydrogens alpha to ketones, however.

Nomenclature

The names for simple ethers (i.e. those with none or few other functional groups) are a composite of the two substituents followed by "ether." Methyl ethyl ether (CH₃OC₂H₅), diphenylether (C₆H₅OC₆H₅). IUPAC rules are often not followed for simple ethers. As for other organic compounds, very common ethers acquired names before rules for nomenclature were formalized. Diethyl ether is simply called "ether," but was once called ''sweet oil of vitriol''. Methyl phenyl ether is anisole, because it was originally found in aniseed. The aromatic ethers include furans. Acetals (α-alkoxy ethers R-CH(-OR)-O-R) are another class of ethers with characteristic properties.

In the IUPAC nomenclature system, ethers are named using the general formula ''"alkoxyalkane"'', for example CH₃-CH₂-O-CH₃ is methoxyethane. If the ether is part of a more complex molecule, it is described as an alkoxy substituent, so -OCH₃ would be considered a ''"methoxy-"'' group. The simpler alkyl radical is written in front, so CH₃-O-CH₂CH₃ would be given as ''methoxy''(CH₃O)''ethane''(CH₂CH₃). The nomenclature of describing the two alkyl groups and appending ''"ether"'', e.g. ''"ethyl methyl ether"'' in the example above, is a trivial usage.

Polyethers

Polyethers are compounds with more than one ether group.

The crown ethers are examples of low-molecular polyethers. Some toxins produced by dinoflagellates such as brevetoxin and ciguatoxin are in a class known as ''cyclic'' or ''ladder'' polyethers.

Polyether generally refers to polymers which contain the ether functional group in their main chain. The term glycol is reserved for low to medium range molar mass polymer when the nature of the end-group, which is usually a hydroxyl group, still matters. The term "oxide" or other terms are used for high molar mass polymer when end-groups no longer affect polymer properties.

Aliphatic polyethers

Step-growth polymerisation of formaldehyde Polyethylene oxide (PEO) or polyoxyethylene (POE) Polypropylene oxide (PPO) ou polyoxypropylene) (POP) Polytetrahydrofuran (PTHF)

Name of the polymers with low to medium molar mass !! Name of the polymers with high molar mass !! Preparation !! Repeating unit !! Examples of trade names
Paraformaldehyde	Polyoxymethylene plastic>Polyoxymethylene (POM) or polyacetal or polyformaldehyde	|	-CH2O-	Delrin from DuPont
Polyethylene glycol (PEG)	|	Ring-opening polymerization of ethylene oxide	-CH2CH2O-	Dow Chemical Company>Dow
Polypropylene glycol (PPG)	|	Anionic addition polymerization>Anionic ring-opening polymerization of propylene oxide	-CH2CH(CH3)O-
Polytetramethylene glycol (PTMG) or Polytetramethylene ether glycol (PTMEG)	|	Acid-catalyzed ring-opening polymerization of tetrahydrofuran	-CH2CH2CH2CH2O-	Terathane from Invista and PolyTHF from BASF

Aromatic polyethers

The phenyl ether polymers are a class of polyethers containing aromatic cycles in their main chain: Polyphenyl ether (PPE) and Poly(p-phenylene oxide) (PPO).

Related compounds

Many classes of compounds with C-O-C linkages are not considered ethers: Esters (R-C(=O)-O-R), hemiacetals (R-CH(-OH)-O-R), carboxylic acid anhydrides (RC(=O)-O-C(=O)R).

Physical properties

Ether molecules cannot form hydrogen bonds with each other, resulting in a relatively low boiling points compared to those of the analogous alcohols. The difference, however, in the boiling points of the ethers and their isometric alcohols becomes lower as the carbon chains become longer, as the van der Waals interactions of the extended carbon chain dominates over the presence of hydrogen bonding.

Ethers are slightly polar. The C-O-C bond angle in the functional group is about 110°, and the C-O dipoles do not cancel out. Ethers are more polar than alkenes but not as polar as alcohols, esters, or amides of comparable structure. However, the presence of two lone pairs of electrons on the oxygen atoms makes hydrogen bonding with water molecules possible.

Cyclic ethers such as tetrahydrofuran and 1,4-dioxane are miscible in water because of the more exposed oxygen atom for hydrogen bonding as compared to aliphatic ethers.

{| style="width:100%;" class="wikitable" |- style="background:#ffdead;" ! colspan="6" | Selected data about some alkyl ethers |- ! Ether ! Structure ! m.p. (°C) ! b.p. (°C) ! Solubility in 1 liter of H₂O ! Dipole moment (D) |- | Dimethyl ether || CH₃-O-CH₃ || -138.5 || -23.0 || 70 g || 1,30 |- | Diethyl ether || CH₃CH₂-O-CH₂CH₃ || -116.3 || 34.4 || 69 g || 1.14 |- | Tetrahydrofuran || O(CH₂)₄|| -108.4 || 66.0 || Miscible || 1.74 |- | Dioxane || O(C₂H₄)₂O|| 11.8 || 101.3 || Miscible || 0.45 |} 

==Reactions== Ethers in general are of low chemical reactivity, but they are more reactive than alkanes (epoxides, ketals, and acetals are unrepresentative classes of ethers and are discussed in separate articles). Important reactions are listed below.

Ether cleavage

Although ethers resist hydrolysis, they are cleaved by mineral acids such as hydrobromic acid and hydroiodic acid. Hydrogen chloride cleaves ethers only slowly. Methyl ethers typically afford methyl halides: :ROCH₃ + HBr → CH₃Br + ROH These reactions proceed via onium intermediates, i.e. [RO(H)CH₃]⁺Br^-.

Some ethers rapidly cleave with boron tribromide (even aluminium chloride is used in some cases) to give the alkyl bromide. Depending on the substituents, some ethers can be cleaved with a variety of reagents, e.g. strong base.

Peroxide formation

Primary and secondary ethers with a CH group next to the ether oxygen form peroxides, e.g. diethyl ether peroxide. The reaction requires oxygen (or air) and is accelerated by light, metal catalysts, and aldehydes. The resulting peroxides can be explosive. For this reason, diisopropyl ether and THF are often avoided as solvents.

Lewis bases

Ethers serve as Lewis bases and Bronsted bases. Strong acids protonate the oxygen to give "onium ions." For instance, diethyl ether forms a complex with boron trifluoride, i.e. diethyl etherate (BF₃^.OEt₂). Ethers also coordinate to Mg(II) center in Grignard reagents. Polyethers, including many antibiotics, cryptands, and crown ethers, bind alkali metal cations strongly.

Alpha-halogenation

This reactivity is akin to the tendency of ethers with alpha hydrogen atoms to form peroxides. Chlorine gives alpha-chloroethers.

==Synthesis== Ethers can be prepared in the laboratory in several different ways.

Dehydration of alcohols

The Dehydration of alcohols affords ethers: : 2 R-OH → R-O-R + H₂O at high temperature This direct reaction requires elevated temperatures (about 125 °C). The reaction is catalyzed by acids, usually sulfuric acid. The method is effective for generating symmetrical ethers, but not unsymmetrical ethers. Diethyl ether is produced from ethanol by this method. Cyclic ethers are readily generated by this approach. Such reactions must compete with dehydration of the alcohol: : R-CH₂-CH₂(OH) → R-CH=CH₂ + H₂O

The dehydration route often requires conditions incompatible with delicate molecules. Several milder methods exist to produce ethers.

Williamson ether synthesis

Nucleophilic displacement of alkyl halides by alkoxides : R-ONa + R'-X → R-O-R' + NaX This reaction is called the Williamson ether synthesis. It involves treatment of a parent alcohol with a strong base to form the alkoxide, followed by addition of an appropriate aliphatic compound bearing a suitable leaving group (R-X). Suitable leaving groups (X) include iodide, bromide, or sulfonates. This method usually does not work well for aryl halides (e.g. bromobenzene (see Ullmann condensation below). Likewise, this method only gives the best yields for primary halides. Secondary and tertiary halides are prone to undergo E2 elimination on exposure to the basic alkoxide anion used in the reaction due to steric hindrance from the large alkyl groups.

In a related reaction, alkyl halides undergo nucleophilic displacement by phenoxides. The R-X cannot be used to react with the alcohol. However, phenols can be used to replace the alcohol, while maintaining the alkyl halide. Since phenols are acidic, they readily react with a strong base like sodium hydroxide to form phenoxide ions. The phenoxide ion will then substitute the -X group in the alkyl halide, forming an ether with an aryl group attached to it in a reaction with an SN2 mechanism.

: C₆H₅OH + OH^- → C₆H₅-O^- + H₂O

: C₆H₅-O^- + R-X → C₆H₅OR

Ullmann condensation

The Ullmann condensation is similar to the Williamson method except that the substrate is an aryl halide. Such reactions generally require a catalyst, such as copper.

Electrophilic addition of alcohols to alkenes

Alcohols add to electrophilically activated alkenes. : R₂C=CR₂ + R-OH → R₂CH-C(-O-R)-R₂ Acid catalysis is required for this reaction. Often, mercury trifluoroacetate (Hg(OCOCF₃)₂) is used as a catalyst for the reaction, geneating an ether with Markovnikov regiochemistry. Using similar reactions, tetrahydropyranyl ethers are used as protective groups for alcohols.

Preparation of epoxides

Epoxides are typically prepared by oxidation of alkenes. The most important epoxide in terms of industrial scale is ethylene oxide, which is produced by oxidation of ethylene with oxygen. Other epoxides are produced by one of two routes:

By the oxidation of alkenes with a peroxyacid such as m-CPBA.

By the base intramolecular nucleophilic substitution of a halohydrin.

Important ethers

	Ethylene oxide	The smallest cyclic ether.
	Dimethyl ether
	Diethyl ether	A common low boiling solvent (b.p. 34.6°C), and an early anaesthetic. Used as starting fluid for diesel engines.
	Dimethoxyethane (DME)	A high boiling solvent (b.p. 85°C):
	Dioxane	A cyclic ether and high boiling solvent (b.p. 101.1°C).
	Tetrahydrofuran (THF)	A cyclic ether, one of the most polar simple ethers that is used as a solvent.
	Anisole (methoxybenzene)	An aryl ether and a major constituent of the essential oil of anise seed.
	Crown ethers	Cyclic polyethers that are used as phase transfer catalysts.
	Polyethylene glycol (PEG)	A linear polyether, e.g. used in cosmetics and pharmaceuticals.

References

External links

ILPI page about ethers.

An Account of the Extraordinary Medicinal Fluid, called Aether, by M. Turner, circa 1788, from Project Gutenberg

Category:Ethers Category:Functional groups

ar:إيثر be-x-old:Простыя этэры bg:Етер (химия) ca:Èter cs:Ethery da:Æter (kemi) de:Ether et:Eetrid el:Αιθέρες es:Éter (química) eo:Etero (kemio) fa:اتر fr:Éther-oxyde ko:에테르 (화학) id:Eter it:Eteri he:אתר (כימיה) kk:Жай эфирлер la:Aether (chemica) lv:Ēteri lt:Eteriai hu:Éter (kémia) mk:Етер nl:Ether (scheikunde) ja:エーテル (化学) no:Eter (kjemi) nn:Eterar pl:Etery pt:Éter ro:Eter ru:Простые эфиры sl:Eter sr:Етар (хемија) sh:Etar (hemija) fi:Eetteri sv:Etrar te:ఈథరు tr:Eter (kimya) uk:Прості ефіри vi:Ete zh:醚

The Gang of Four () was the name given to a political faction composed of four Chinese Communist Party officials. They came to prominence during the Cultural Revolution (1966–76) and were subsequently charged with a series of treasonous crimes. The members consisted of Jiang Qing, Mao Zedong's last wife as the leading figure of the group, and her close associates Zhang Chunqiao, Yao Wenyuan, and Wang Hongwen.

The Gang of Four effectively controlled the power organs of the Communist Party of China through the latter stages of the Cultural Revolution, although it remains unclear which major decisions were made through Mao Zedong and carried out by the Gang, and which were the result of the Gang of Four's own planning.

The Gang of Four, together with disgraced Communist general Lin Biao, were labeled the two major "counter-revolutionary forces" of the Cultural Revolution and officially blamed by the Chinese government for the worst excesses of the societal chaos that ensued during the ten years of turmoil. Their downfall in a ''coup d'état'' on October 6, 1976, a mere month after Mao's death, brought about major celebrations on the streets of Beijing and marked the end of a turbulent political era in China.

Formation

The group was led by Jiang Qing, and consisted of three of her close associates, Zhang Chunqiao, Yao Wenyuan, and Wang Hongwen. Two other men who were already dead in 1976, Kang Sheng and Xie Fuzhi, were named as having been part of the "Gang". Chen Boda and Mao Yuanxin, the latter being Mao's nephew, were also considered some of the Gang's closer associates.

Most Western accounts consider that the actual leadership of the Cultural Revolution consisted of a wider group, referring predominantly to the members of the Central Cultural Revolution Group. Most prominent was Lin Biao, until his purported flight from China and death in a plane crash in 1971. Chen Boda is often classed as a member of Lin's faction rather than Jiang Qing's.

Role

The removal of this group from power is sometimes considered to have marked the end of the Cultural Revolution, which had been launched by Mao in 1966 as part of his power struggle with leaders such as Liu Shaoqi, Deng Xiaoping and Peng Zhen. Mao placed Jiang Qing, who before 1966 had not taken a public political role, in charge of the country’s cultural apparatus. Zhang, Yao and Wang were party leaders in Shanghai who had played leading roles in securing that city for Mao during the Cultural Revolution.

Around the time of the death of Lin Biao, the Cultural Revolution began to lose impetus. The new commanders of the People's Liberation Army demanded that order be restored in light of the dangerous situation along the border with the Soviet Union (see Sino-Soviet split). The Premier, Zhou Enlai, who had accepted the Cultural Revolution but never fully supported it, regained his authority, and used it to bring Deng Xiaoping back into the Party leadership at the 10th Party Congress in 1973. Liu Shaoqi had meanwhile died in prison in 1969.

Near the end of Mao's life, a power struggle occurred between the Gang of Four and the alliance of Deng Xiaoping, Zhou Enlai, and Ye Jianying.

Downfall

It is now officially claimed by the Communist Party of China that Mao in his last year turned against Jiang Qing and her associates, and that after his death on 9 September 1976, they attempted to seize power (the same allegation made against Lin Biao in 1971). Even decades later, it is impossible to know the full truth of these events.

It does appear that their influence was in decline before Mao's death: when Zhou Enlai died in January 1976, he was succeeded not by one of the radicals but by the unknown Hua Guofeng. In April 1976, Hua was officially appointed Premier of the State Council. Upon Mao's death Hua was named Communist Party chairman as well.

The "Gang" had arranged for Deng Xiaoping's purge in April 1976 (however, he would return and by 1978 become the real power of the Party). They hoped that the key military leaders Wang Dongxing and Chen Xilian would support them, but it seems that Hua won the Army over to his side. On 6 October 1976, Hua had the four leading radicals and a number of their lesser associates arrested. A massive media campaign was then launched against them, dubbing them the Gang of Four and blaming them for all the excesses of the Cultural Revolution. (The Chinese words for "four" and "death" are nearly homophones, and thus the moniker contained a second, inauspicious meaning.)

Han Suyin gives a detailed account of their overthrow:

Although not referred to as such in China, because, the Communist Party remained in control, this was effectively a coup d'etat. Beginning on 21 October, nationwide denunciations of the Gang began, which culminated in the December releases of files related to the Gang's alleged crimes to the public. Celebrations were prominent and not limited to the streets of Beijing and other major cities.

Aftermath

Immediately after the coup d’état, Hua Guofeng, who appeared to be Mao's designated successor, Marshall Ye Jianying, and economic czars Chen Yun and Li Xiannian formed the core of the next party leadership. These three, together with the newly rehabilitated Deng Xiaoping and bodyguard coup leader Wang Dongxing were elected party Vice Chairmen at the August 1977 11th National Party Congress. At the politburo level, the membership of all four living marshals, seven other generals and at least five others with close military ties reflected the deep concern for national stability.

Trial

In 1981, the four deposed leaders were subjected to a show trial and convicted of anti-party activities. During the trial, Jiang Qing in particular was extremely defiant, protesting loudly and bursting into tears at some points. She was the only member of the Gang of Four who bothered to argue on her behalf. The defence's argument was that she obeyed the orders of Chairman Mao Zedong at all times. Zhang Chunqiao refused to admit any wrong as well. Yao Wenyuan and Wang Hongwen expressed repentance and confessed their alleged crimes.

The prosecution separated political errors from actual crimes. Among the latter were the usurpation of state power and party leadership; the persecution of some 750,000 people, 34,375 of whom died during the period 1966-76. The official records of the trial have not yet been released.

Jiang Qing and Zhang Chunqiao received death sentences that were later commuted to life imprisonment, while Wang Hongwen and Yao Wenyuan were given life and twenty years in prison, respectively. They were all later released. All members of the Gang of Four have since died; Jiang Qing committed suicide in 1991, Wang Hongwen died in 1992, and Zhang Chunqiao and Yao Wenyuan died in 2005.

Supporters of the Gang of Four, including Chen Boda and Mao Yuanxin, were also sentenced.

"Little Gang of Four"

In the struggle between the conservative Hua Guofeng's clique and the one of Deng Xiaoping, a new term emerged, pointing to Hua's four closest collaborators, Wang Dongxing, Wu De, Ji Dengkui, and Chen Xilian. In 1980, they were charged with "grave errors" in the struggle against the Gang of Four and demoted from the Political Bureau to mere Central Committee membership.

See also

Soviet Union's Anti-Party Group

References

Category:Cultural Revolution Category:Anti-Revisionists 4 Category:Factions of the Communist Party of China Category:Articles about multiple people Category:Maoist terminology Category:History of the People's Republic of China

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Title	Ether Saga Odyssey
Developer	Beijing Perfect World
Publisher	Perfect World Entertainment Gameastor
Released
Genre	Fantasy MMORPG
Modes	MMOG
Ratings	ESRB: Everyone 10+
Platforms	Windows
Media	Download, CD-ROM, DVD
Requirements	Minimum 1.5 GHz Pentium 4 CPU512M RAM 64MB 3D Accelerator graphics card(Pixel and Vertex Shaders 1.4)DirectX 9.0c6.3 (3.0 after installation and extracted files are deleted) GB hard disk space Internet Connection ---- Recommended 1.5 GHz Pentium 4 CPU1GB RAM 128mb 3D Accelerator graphics cardDirectX 9.0c6.3 GB hard disk space Internet Connection
Input	Keyboard, Mouse }}

''Ether Saga Online'' (commonly abbreviated as ESO), is a free to play MMORPG developed by Perfect World Entertainment. The International version has now been released worldwide in an English-language format. Ether Saga launched its closed beta February 2, 2009. The open beta began on March 17, 2009. And was fully released on July 1, 2009.

''Ether Saga Online'' is heavily based on Journey to the West.

Races

Ren is the archetypal human race. The Ren run most of the major cities. They have advanced technology, societies and political systems. Their influence extends far and wide. It is the Human task to collect fragments of the Divine Chalice which were scattered about the world when a clumsy official dropped it.

Shenzu is the Demigod race. These individuals keep mostly to themselves focusing on spiritual cultivation and reaching higher levels of consciousness. They have been instructed to capture a certain pig demon who is actually the reincarnation of a powerful yet unruly heavenly general.

Yaoh were once animals but through advanced spiritual cultivation they were acknowledged by Heaven and granted acceptance as powerful and worthy of respect. Yaoh communities are found in various parts of the land. Their goal is to find a Sacred Ark that was discovered missing during the Peach Yard Banquet. Without this vessel the sacred knowledge cannot be brought to the Middle Kingdom.

Classes

Dragoon Considered as a Tank. Engages in battle using a spear and wears heavy armor.

Rogue Considered as a damage dealer. Uses poison-tipped daggers and wears medium armor.

Mystic is a healer, can cast Buffs. Uses a staff for battle and wears light armor.

Ranger Considered a ranged damage dealer. Can cast debuffs on enemies. Wears medium armor and fights with a bow.

Conjurer is an offensive spell-caster. Can cast positive buffs. Equips amulets and wears light armor in battle.

Shaman is part healer and a secondary tank. Able to cast buffs. Wears heavy armor and fights with a Hammer.

Maven is a spell-caster/healer(half mystic/conjurer).It heals and have good damage. Able to cast buffs.Wears light armors and fight with a scepter

Hellion Considered an offensive class. Has a special system , rage system that means they get mana by being hit. They can sacrifice their own hp to get rage. Wears heavy armor and fights with dual-axes

Features

Pet System Ether Saga Online has an expansive pet system in which pets can be leveled, trained, and combined with each other. All 3 races have a starter pet.

External links

Ether Saga Official Website

Ether Saga US Official Website

Ether Saga Club - English Social-Networking Community Fansite and Wiki

Category:Video games developed in the People's Republic of China

ru:Ether Saga Online zh:口袋西游