Oxirane reactions medium

Since spontaneous polymerization is only observed in contact with air or in undesiccated benzene used as a reaction medium, it is natural to attribute this phenomenon to the catalytic effect of traces of water on the opening of the oxirane ring involved in the coordination interaction with the tin atom. 

At the end of considerations dealing with oxirane/carbon dioxide copolymerisation, copolymerisation run under supercritical conditions in carbon dioxide as the reaction medium should be mentioned [239]. 

In the reaction medium there are two activated species activated oxirane and activated THF [54, 55]. 

Sumitomo developed a recirculation process for manufacture of PO using CHP as oxidant (196). The company developed both a new catalyst and a new process for PO production. The production method is fundamentally similar to known methods involving organic peroxides as oxidants the major difference is that cumene is used as the reaction medium and hence the process is referred to as the cumene PO-only process. Laboratory tests started in 2000 and pilot plant testing in 2001. A plant was completed in 2002 and started up in 2003. This commercial plant was the first PO-only plant in Japan, producing PO by oxidation of propylene with cumene hydroperoxide without a significant formation of coproducts. The plant is located in the Chiba prefecture, operated by a joint venture between Nihon Oxirane Co. and Lyondell, and produces aroimd 200,000 t of PO/year. A second plant was started in May 2009 in Saudi Arabia, as a joint project of Sumitomo with Saudi Arabian Oil Co. 

Decomposition of Caro s acid is catalysed by acetone.324 A kinetic study in aqueous alkaline medium indicates simple second-order kinetics. Nucleophilic addition of S052- to the carbonyl carbon leads to oxirane by reaction with another SOs2- to give... 

Three-membered cyclic compounds can generally be prepared from difunctional compounds by 1,3-elimination. In the formation of oxiranes from 2-substituted alkanols, the alkoxide produced in the basic medium participates in an internal nucleophilic attack, which promotes the departure of the substituent on the adjacent carbon atom leading to ring-closure. A stereochemical condition for the reaction is that the reacting groups should be in an antiperiplanar conformation relative to each other (Eq. 51). 

If use is made of the five-membered cyclic phosphorus derivatives, the geometry of which is more suitable than that of the triphenylphosphine, formation of the phos-phorane intermediate is more favored and the yield of olefin increases. Deoxygenation with KSeCN in mildly alkaline medium can similarly occur by heteroatom exchange retention is observed as a consequence of double inversion. Open-chain compounds react with good yields, but cyclic oxiranes yields vary considerably with the number of ring atoms, due to steric hindrance. Alkali metal 0,0-diethyl-phosphorotellurates are very useful reagents for the conversion of terminal oxiranes, Eq. 104 but the reaction does work for other types. In the case of oxiranes formally derived from acyclic olefins, the (Z) compounds react more readily than the (E)-oxiranes. ... 

Oxiranes can be opened with periodic acid in a phase-transfer system, in an aqueous medium, a dialdehyde is produced (Eq. 157) in the case of a dienemono-oxirane, the double bond remains unchanged in the reaction. ... 

In the presence of anhydrous copper sulfate, aliphatic oxiranes react stereoselect-ively with acetone, but (E)- and (Z)-aryl-aliphatic oxiranes give the same isomer mixture. A study has been made of the kinetics of formation of dioxolanes from oxiranes and aromatic aldehydes in a neutral medium. Dioxolane and dioxan isomers are obtained from the reaction of 2,3-epoxybutane and carbonyl compounds. ... 

The mechanism of the reaction has been studied in basic, acidic, and neutral media. In basic medium, the reaction is a substitution of 87 2 type, the mechanism and stereochemistry of which have been reasonably well clarified. In asymmetric oxiranes, the attack by the nucleophile generally takes place with inversion on the less-substituted carbon atom (Eq. 297). 

The mechanism of the opening in acidic medium is not so simple. Although a general reaction scheme can be written, the pathway is influenced to a great extent by the structure of the oxirane, the steric and electronic effects of the substituents, and the solvent also plays an important role. Ever-increasing attention is being paid to the concept of the microscopic structure of solvation in binary solvents. In binary solvent mixtures, the structure of the solvent around the molecule in the solvent shell differs from that of bulk solvent. 

The great variety of transformations that can occur with other sulfur-containing nucleophiles are illustrated by the following experimental observations. Oxiranes react with sulfurated borohydrides in a similar way as the hydrogen sulfide in a basic medium symmetric bis hydroxyethyl disulfides are formed. c/s-benzene trioxide gives di- and triadducts with A, A-diphenylthiocarbamide. Reports have appeared on the reactions between oxirane and -decylmercaptan, butadiene-monooxirane derivatives and mercaptans, and methyloxirane and sulfite ion. ... 

Oxiranes yield oxazolines with nitriles in the presence of strong acids. The reaction proceeds with inversion, with complete stereospecificity. A new application of the Ritter reaction has been reported the opening of epimeric steroid-16,17-oxiranes in acidic medium with acetonitrile. The reactions of unsaturated hydroxynitriles formed from a-ethylenic oxiranes have been investigated. Numerous publications have appeared on the kinetics of reactions with carboxylic acids and their derivatives. ° ... 

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