Glycols, cyclic oxidative

A simple cyclic diester of carbonic acid is ethylene carbonate (7.96), a chemical with a toxicity profile resembling that of ethylene glycol (7.97). Metabolic studies have confirmed that ethylene carbonate is hydrolyzed very rapidly to ethylene glycol (whose oxidation is discussed in Chapt. 2 in [7]) and C02. Indeed, rats given an oral dose of ethylene carbonate did not excrete the unchanged xenobiotic in detectable amounts, and blood levels of the diester were ca. 100-fold smaller than those of ethylene glycol [178],... 

Ethylene Glycol under Glycols Ethylene Oxide under Cyclic Ethers... 

Treatment of polymethylene glycols with 50% sulfuric acid gives mixtures of cyclic oxides. Thus, 1,6-hexanediol yields a mixture containing 16% 1,6-, 25% 1,5-, and 65% 1,4-oxidohexane. In other instances, formation of the 1,4-oxido derivatives is also favored. ... 

Corresponding vinyl ethers are formed only to a minor extent. Their formation can, however, be favored by diluting the reaction mixture with an inert solvent [2]. With glycols, cyclic acetals are obtained, e. g., dioxolanes from 1,2-glycols and 1,3-dioxanes from 1,3-glycols [97]. This reaction has been claimed as an alternative to the Wacker route producing acetaldehyde when it is carried out in the presence of suitable oxidants. 

ETHYLENE GLYCOL CYCLIC CARBONATE (96-49-1) Combustible liquid (flash point 289°F/143°C). Reacts with strong oxidizers. Incompatible with fluorine, germanium, lead diacetate, magnesium, mercurous chloride, nitrates, silicon, silver nitrate, titanium. 

Poly(ethylene terephthalate) is the condensation polymer made from terephthalic acid and ethylene glycol. The acid or its dimethyl ester is obtained by the oxidation of -xylene, a product from catalytic reforming of naphtha. The glycol is obtained from ethane via the corresponding cyclic oxide. With the availability of purified terephthalic acid since the 1960s direct esterification of the acid in a continuous process is used in commercial production of the polyester [31] ... 

Regioselectivity of C—C double bond formation can also be achieved in the reductiv or oxidative elimination of two functional groups from adjacent carbon atoms. Well estab llshed methods in synthesis include the reductive cleavage of cyclic thionocarbonates derivec from glycols (E.J. Corey, 1968 C W. Hartmann, 1972), the reduction of epoxides with Zn/Nal or of dihalides with metals, organometallic compounds, or Nal/acetone (seep.lS6f), and the oxidative decarboxylation of 1,2-dicarboxylic acids (C.A. Grob, 1958 S. Masamune, 1966 R.A. Sheldon, 1972) or their r-butyl peresters (E.N. Cain, 1969). 

Polyether Polyols. Polyether polyols are addition products derived from cyclic ethers (Table 4). The alkylene oxide polymerisation is usually initiated by alkah hydroxides, especially potassium hydroxide. In the base-catalysed polymerisation of propylene oxide, some rearrangement occurs to give aHyl alcohol. Further reaction of aHyl alcohol with propylene oxide produces a monofunctional alcohol. Therefore, polyether polyols derived from propylene oxide are not truly diftmctional. By using sine hexacyano cobaltate as catalyst, a more diftmctional polyol is obtained (20). Olin has introduced the diftmctional polyether polyols under the trade name POLY-L. Trichlorobutylene oxide-derived polyether polyols are useful as reactive fire retardants. Poly(tetramethylene glycol) (PTMG) is produced in the acid-catalysed homopolymerisation of tetrahydrofuran. Copolymers derived from tetrahydrofuran and ethylene oxide are also produced. 

Dicyano-l,2,3-trithiole 2-oxide (143) has been prepared from the silver salt of 2,3-dimercaptomaleonitrile (142) and thionyl chloride (66HC(2l-i)67). Similarly, the reaction of ethylene glycol (144) with thionyl chloride gave 1,3,2-dioxathiolane 2-oxide (145), the parent compound of saturated five-membered cyclic sulfites (see Chapter 4.33). 

However, the cyclic-intermediate mechanism cannot account for all glycol oxidations, since some glycols that cannot form such an ester (e.g., 12) are nevertheless cleaved by lead tetraacetate... 

The mechanism of oxidation probably involves in most cases the initial formation of a glycol (15-35) or cyclic ester,and then further oxidation as in 19-7. In line with the electrophilic attack on the alkene, triple-bonds are more resistant to oxidation than double bonds. Terminal triple-bond compounds can be cleaved to carboxylic acids (RC=CHRCOOH) with thallium(III) nitrate or with [bis(trifluoroacetoxy)iodo]pentafluorobenzene, that is, C6F5l(OCOCF3)2, among other reagents. 

The solvent isotope effect suggests that no O-H cleavage is involved in the slow step and the effect of O-methylation indicates that a cyclic complex is involved. The induction factor is probably obscured by the reaction of Mn(III) and Mn02 with pinacol itself. The typical glycol-cleavage mechanism advocated for oxidations by Pb(IV) and I(VII) (p. 349) may well operate, viz. 

The most widely used reagent for oxidation of alkenes to glycols is osmium tetroxide. Osmium tetroxide is a highly selective oxidant that gives glycols by a stereospecific syn addition.39 The reaction occurs through a cyclic osmate ester that is formed by a [3 + 2] cycloaddition.40... 

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