Physical Properties of Oxiranes

Oxirane (1) and methyloxirane (3) are miscible with water, ethyloxirane is very soluble in water, while compounds such as cyclopentene oxide and higher oxiranes are essentially insoluble (B-73MI50501) (for a discussion of the solubilities of heterocycles, see (63PMH(l)l77)). Other physical properties of heterocycles, such as dipole moments and electrochemical properties, are discussed in various chapters of pmh. The optical activity of chiral oxiranes has been investigated by ab initio molecular orbital methods (8UA1023). 

EtO (oxirane, epoxyethane, and dimethylene oxide) is a colorless gas condensing at low temperatures to a mobile liquid. It is miscible in all proportions with water, alcohol, ether, and most organic solvents. Its vapors are flammable and explosive. The physical properties of EtO are summarized in Table 1. 

The oxirane rings are responsible for the physical properties and the low shrinkage, while the hydrophobic properties of the material are related to the siloxanes [61]. As a consequence, exogenous discolouration and water absorption are reduced. All these reported advantageous characteristics serve to enhance the potential of silorane monomers to be used successfully in dental composite materials. Weinmann et al. [54] observed a low shrinkage rate (<1 %) and seven times more light stability for the silorane in comparison with resin-based methacrylates. The clinical application of siloranes is limited to the posterior teeth because only a few low translucent colours are available. Additionally, due to its hydrophobic properties, a special adhesive system must be used for silorane restorations. 

Eick, J.D., Kostoryz, E.L., Rozzi, S.M., Jacobs, D.W., Oxman, J.D., Chappelow, C.C., et al. Invitro biocompatibility of oxirane/polyol dental composites with promising physical properties. Dent. Mater. 18, 413-421 (2002)... 

Carbon dioxide is considered to be an interesting alternative to most traditional solvents [17, 18] because of its practical physical and chemical properties it is a solvent for monomers and a non-solvent for polymers, which allows for easy separation. To a somewhat lesser extent, it can also be a sustainable source of carbon [19]. The use of CO2 as a reactant is considered to contribute to the solution of the depletion of fossil fuels and the sequestration of the greenhouse gas CO2. One example in this area is the copolymerization of carbon dioxide with oxiranes to aliphatic polycarbonates [19-22]. 

Synonyms 1,2-Epoxyethane Oxirane (Chemical Formula CHjCHjO (ii) Observable Characteristics — Physical State (asshipped) Liquid Color Colorless Odor Sweet characteristic ether-like (iii) Physical and Chemical Properties — Physical State at 15 C and I atm Gas Molecular Weight 44,05 Boiling Point at I atm 51,1, 10,6, 283,8 Freezing Point -107,7, -112,6, 160,6 Critical Temperature 385, 196, 469 Critical Pressure 1,040,71,0, 72 Specific Gravity 0,869 at 20 "C (liquid) Vapor (Gas) Specific Gravity 1,5 Ratio of Specific Heats of Vapor (das) 1.212 Latent Heat of Vaporization 249.3, 138.5, 5.799 Heat of Combustion -11,480, -34,... 

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