During the early stage of the copolymerization of trioxane and ethylene oxide, we found the formation of three novel cyclic compounds: 1,3,5,7-tetraoxacyclononane (TOCN), 1,3,5,7,10-pentaoxacyclododecane (POCD), and 1,3,5,7,10,13-hexaoxacyclopentadecane (HOCP). These novel cyclic compounds were new direct reaction products of 1 mole of trioxane and 1 mole of ethylene oxide, 1 mole of trioxane and 2 moles of ethylene oxide, and 1 mole of trioxane and 3 moles of ethylene oxide, respectively. We compared the 1H-NMR and 13C-NMR spectra of each cyclic compound and precisely assigned the signals of each spectrum using NOESY (nuclear Overhauser enhancement spectroscopy) and HETCOR (heteronuclear correlated spectroscopy). We also compared the 1H-NMR spectra of POCD and HOCP with the corresponding cyclic formals with one oxymethylene unit, diethylene glycol formal (DEGF) and triethylene glycol formal (TEGF). Interestingly, we found that DEGF and TEGF, which have only one oxymethylene unit, showed no proton splitting of the oxyethylene units, while POCD and HOCP, which have three consecutive oxymethylene units, have split signals for the oxyethylene units.
An NMR method for the analysis of the ethylene oxide sequence of the acetal copolymer from trioxane and ethylene oxide has not yet been established. We found three novel cyclic compounds composed of 1 mol of ethyelene oxide and 1 mol of trioxane, 2 mol of ethylene oxide and 1 mol of trioxane, and 3 mol of ethylene oxide and 1 mol of trioxane. These compounds gave only one consecutive oxyethylene unit, two consecutive oxyethylene units, and three consecutive oxyethylene units in three consecutive oxymethylene units, respectively, and gave different 1 H NMR spectra for each oxyethylene unit. Considering these data, we synthesized three polymeric model compounds that have one consecutive oxyethylene sequence, two consecutive oxyethylene sequences, and three consecutive oxyethylene sequences in an oxymethylene main chain. By a linear combination of the 1 H NMR spectrum of each oxyethylene unit of the three polymeric model compounds, we succeeded in determining the ethylene oxide sequence by the 1 H NMR method for the copolymer from trioxane and ethylene oxide. Good agreement was observed between the 1 H NMR method and the hydrolysis method for the analysis of the ethylene oxide sequences.
Novel reactions between trioxane and ethylene oxide were discovered, and three novel cyclic formals were isolated and identified. These novel cyclic compounds clarified the initiation mechanism of the copolymerization of trioxane and ethylene oxide. This type of reaction was not limited to the reaction between trioxane and ethylene oxide but was also generalized to the reaction between the cyclic formal and ethylene oxide. Although an NMR method for analyzing the ethylene oxide sequences of the acetal copolymer from trioxane and ethylene oxide has not yet been established, the three newly found novel cyclic compounds, composed of 1 mol of ethylene oxide and 1 mol of trioxane, 2 mol of ethylene oxide and 1 mol of trioxane, and 3 mol of ethylene oxide and 1 mol of trioxane, were useful for analyzing the ethylene oxide sequences. These compounds gave only one consecutive oxyethylene unit, two consecutive oxyethylene units, and three consecutive oxyethylene units in three consecutive oxymethylene units, respectively, and gave different 1H NMR spectra for each oxyethylene unit. Considering these data, we synthesized three polymeric model compounds that had one consecutive oxyethylene sequence, two consecutive oxyethylene sequences, and three consecutive oxyethylene sequences in an oxymethylene main chain. By a linear combination of the 1H NMR spectrum of each oxyethylene unit of the three polymeric model compounds, we succeeded in determining the ethylene oxide sequences by the 1H NMR method for the copolymer from trioxane and ethylene oxide. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 520–533, 2004
The direct reaction of ethylene oxide with trioxane was thought impossible because of the weak basicity of trioxane. Thus, as the initiation mechanism of the copolymerization of trioxane and ethylene oxide, the formation mechanism of dioxolane from ethylene oxide and formaldehyde was proposed by several authors, and this mechanism was thought plausible for a long time.We found a new reaction, that is, the direct reaction of ethylene oxide with trioxane and isolated a novel cyclic formal. From this novel cyclic formal, 1,3,5-trioxepane was formed and then dioxolane was also generated. A new intermediate, or a novel cyclic compound, was separated using a micro-distillation apparatus. Its chemical structure was confirmed using 'H-NMR, 13C-NMR, Mass spectrum and elemental analysis. The new isolated intermediate or novel cyclic compound was 1,3,5,7-tetraoxacyclononane, which identifies a new direct reaction between trioxane and ethylene oxide. This reaction identified the precise initiation mechanism of the copolymerization of trioxane and ethylene oxide.
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