Epoxy groups, formation

Lee, M., Lenman, M., Banas, A., Bafor, M., Singh, S., Schweizer, M., Nilsson, R., Liljenberg, C., Dahlqvist, A., Gummeson, P.O., Sjodahl, S., Green, A., and Stymne, S. Identification of non-heme diiron proteins that catalyze triple bond and epoxy group formation. Science 280, 915-918, 1998. 

Figure 7.18 Amine-containing dendrimers can be activated with epibromohydrin to result in the formation of reactive epoxy groups on the dendrimer surface. This reactive intermediate then can be used to conjugate with thiol-containing proteins, such as thiolated alkaline phosphatase. The reaction results in the formation of a thioether bond.

To further verify the importance of epoxy groups for the composite or composite formation and the effects of this process on the porosity of the final materials, an attempt was made to build the composite of HKUST-1 with various graphites [36]. In the resulting materials the synergetic effect of the increase in the porosity was not found and... 

Fig. 10.24. Simplified metabolism of buta-1,3-diene (10.101), showing the formation of reactive metabolites bearing an epoxy group (i.e., 10.102, 10.103, and 10.105) or an a,(5-unsatu-rated carbonyl moiety (e.g., 10.109 and 10.110)...

Other renewable resources sorbitol (I), cellobiose (XXV), etc. can be used in similar ways as starting materials in the preparation of epoxy resins. We are now working on a direct two-step preparation of diepoxy sorbitol derivatives by direct halogenation of the two primary hydroxyl groups with the formation of 1,6-dichloro-1,6-dideoxy-sorbitol, (XXIII), followed by epoxy ring formation (1,2 5,6-dianhydrosorbitol (XXIV) ... 

The question then arises if a regioselective opening of a 2,3-rraMS-epoxy carboxamide derived from aldonic acids would occur. The 2,5-di-O-tosyl-D-ribono-1,4-lactone (62) (Scheme 13) was used to find an answer to this question. If treated with ammonia, the 2,5-diamino-2,5-dideoxy-D-ribono-1,5-lactam (63) was obtained as the only product [79]. The NMR spectra of the reaction mixture showed the formation of the diepoxy amide A which was opened at C-5 by ammonia. In this case no internal lactamization could occur, due to the trans 2,3-epoxy group in B (Scheme 13). Thus, a regioselective opening of an acyclic 2,3-epoxy carboxamide took place at C-2. The reaction was complete within 6 days. 

Propenal and the S.A. group formation must form from decomposition of the P.A.-E, S.A.-E, and E-OH cure reaction products. However, because we observe the S.A. group formation is most prevalent for low DDS concentration TGDDM-DDS epoxies, which contain a higher concentration of E-OH cure reaction products, then we suggest propenal and S.A. group formation most likely occurs by decomposition of non-cyclized (10) and cyclized (11) E-OH reaction products, (see next Sect. Rates and Chemistry of Cure Reactions)... 

Terpolymers made from two different olefins and CO are known. They were first described in Brubaker s initial patent and involved the free radical initiated terpolymerization of CO and C2H with another olefin such as propylene, isobutylene, butadiene, vinyl acetate, diethyl maleate or tetrafluoroethylene More recently, in another patent, Hammer has described the free radical initiated terpolymerization of CO and C2H with vinyl esters, vinyl ethers or methyl methacrylate 26Reaction temperatures of 180-200 °C and a combined pressure of 186 MPa were employed. Typically a CO QH4 olefin molar ratio of 10 65 25 was observed in the terpolymers. In other patents, Hammer 27,28) has described the formation of copolymers with pendant epoxy groups by the free radical initiated polymerization of CO, QH4, vinyl acetate and glycidyl methacrylate. Reaction conditions similar to those stated above were employed, and a typical CO C2H vinyl acetate glycidyl methacrylate molar ratio of 10 65 20 5 was observed in the product polymer. 

It was found that the initial reaction rate was equal to YoAo, where Yo and Ao are the initial concentrations of epoxy groups and m-phenyl diamine. Formation of hydroxyl groups during the reaction leads to self-acceleration. This prediction was confirmed by measurements carried out in an isothermal regime, because adiabatic conditions for a reaction lead to self-acceleration due to an increase in temperature (see above). Thus, the initial reaction rate vo can be expressed as... 

Figure 3.13 shows the variation of the gel conversion of the limiting reactant as a function of the stoichiometric ratio. For r > 3, no gel is formed and the polymer remains in the liquid state after complete reaction of epoxy groups. If the amount of epoxy monomer necessary to obtain a stoichiometric system is added in a second step, polymerization restarts, leading to gelation and the formation of a network. The two-step polymerization is the basis of several commercial thermosetting polymers. 

However, for several epoxy-amine systems, the simple kinetic model expressed by the set of Eqs (5.18) (5.21) does not provide a good fitting with experimental results. Reaction mechanisms, including the formation of different kinds of complexes, have been postulated to improve the kinetic description (Flammersheim, 1998). Also, a more general treatment of the kinetics of epoxy-amine reactions would have to include the possibility of the homopolymerization of epoxy groups in the reaction path. Sets of kinetic equations including this reaction have been reported (Riccardi and Williams, 1986 Chiao, 1990 Cole, 1991). 

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