1,3,5 Trioxepane

The next structural study of polydioxolans of DP ranging from 7 to 70 by Plesch and Westermann [6] confirmed the regular structure of the polymer. It was also shown that when a polydioxolan was formed and then depolymerised in solution by perchloric acid, the only product was monomer. This is apparently in conflict with the findings of Miki, Higashimura, and Okamura [7] who reported that a reaction mixture, in which dioxolan had been polymerised for 3 hours at 35 °C by BF3-Et20, contained 1,3,5-trioxepan, 1,4-dioxane, trioxane, and other compounds. Most probably the difference is at least partly due to the long reaction time and the use of boronfluoride, which is well known to produce more side-reactions than protonic acids. 

For instance, Jaacks and Boehlke [16] reported that for 1 with perchloric acid in methylene dichloride at 30 °C, water caused the formation of 1,3,5-trioxepane, mol for mol, and... 

Other cyclic acetals that have been studied are 1,3,5-trioxane, 1,3,5-trioxepane, 1,3,6,9-tetraoxacycloundecane, and 1,3,5,7-tetroxocane (also referred to as 1,3,5,7-tetroxane) [Kawakami and Yamashita, 1979 Munoz-Escalona, 1978 Schulz et al., 1984 Szwarc and Perrin, 1979]. Polymerization of bicyclic acetals has been of interest for synthesizing polysaccharides [Good and Schuerch, 1985 Hirasawa et al., 1988 Okada, 1991 Okada et al., 1989 Sumitomo and Okada, 1984]. 

Polymerization of 1,3,5-trioxepane involves more complicated propagation-depropagation equilibria. The initially formed oxycarbocation XX loses formaldehyde to yield oxycarbocation XXI, which in turn loses 1,3-dioxolane to regenerate XX ... 

No information on 1,3,5-trioxepins and 1,3,5-trithiepins as well as on oxadithiepins and dioxathiepins appeared in CHEC(1984) or CHEC-II(1996). The monocyclic disubstituted 1,3,5-trioxepane was synthesized by multicomponent cyclocondensation (Section 13.16.9.5). The most common approach to various fused and bridged trioxepanes,... 

The formation of cyclic oligomers in the polymerization of tetrahydrofuran has not been observed (23). In the case of 1,3-dioxolane small amounts of oligomers going from dimer to nonamer have been isolated (24). Under the influence of borontrifluo-ride etherate in methylene chloride at 35 °C small amounts of 1,3,5-trioxepane are formed (25). Miki, Higashimura and Okamura (25) ascribed the formation of this substance to a backbiting reaction in the polymerization of dioxolane ... 

Tetraoxonane 113 underwent a ring contraction to afford 1,3,5-trioxepane 114, which is also observed as the main by-product of the tetraoxonane synthesis (Equation 2) <1998CC1809, 2001TL271> (Chapter 13.16). 

New investigations into the kinetics of monomeric formaldehyde copolymerization were subsequently conducted. In papers63,64 a degradation kinetics method for the analysis of polyacetal microstructure is proposed in paper6 5 is outlined a pyrolitie method based on a chromatographic determination of 1,3,5-trioxepane at the junctions of oxymethylene and dioxolane blocks. 

Fig. 9. Kinetic curves of the reagents conversion in liquid-phase cationic copolymerization of formaldehyde with 1,3-dioxolane. 1) 1,3 dioxolane consumption 2) 1,3,5-trioxepane yield 3) yield of ethylene oxide units in copolymer 4) yield of soluble polymer...

Monomer equilibrium concentrations in copolymerization will be discussed in more detail in the next section, which is devoted to the polymerization of 1,3,5-trioxepane. 

Certain cyclic monomers are build up from two or more other simpler compounds which can serve as monomers by themselves. Thus, during the polymerization of more complex cyclic monomers simpler structures may emerge during the polymerization process. Szwarc 83) for the first time quantitatively treated the thermodynamics of polymerization of such a composite monomer, reevaluating the experimental data of Schulz et al. M). Below we follow Szwarc s reasoning applied for the cationic polymerization of 1,3,5-trioxepane (TXP), a monomer comprising formaldehyde (FA) and 1,3-dioxolane (DXL). Under equilibrium conditions besides the unreacted monomer both FA and DXL are also present ... 

For TOX copolymerization with ethylene oxide (EO), EO was first converted to low molecular weight copolymer and cyclic oligomers such as dioxolane (DOL) and 1,3,5-trioxepane (TOP) (4). For either EO and DOL as comonomer with TOX, they were found to be preferentially incorporated during the induction period (5). 

The general equation for determination of the equilibrium cyclization constants for the composed cyclics is in fact the one shown previously in Section 4.04.2 (eqn [24]), because the equilibrium in polymerizations of such monomers is the same as in copolymerization of corresponding simpler monomers (e.g., 1,3,5-trioxepane polymerization versus 1 1 copolymerization of 1,3-dioxolane and formaldehyde). 

Equilibrium in 1,3,5-trioxepane polymerization regarded as an example of the equilibrium copolymerization 62... 

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