Methylene-1,3,5-trioxane

It is marketed as a 35-40 per cent, solution in water (formalin). The rpactions of formaldehyde are partly typical of aldehydes and partly peculiar to itself. By evaporating an aqueous solution paraformaldehyde or paraform (CHjO), an amorphous white solid is produced it is insoluble in most solvents. When formaldehyde is distilled from a 60 per cent, solution containing 2 per cent, of sulphuric acid, it pol5unerises to a crystalline trimeride, trioxane, which can be extracted with methylene chloride this is crystalline (m.p. 62°, b.p. 115°), readily soluble in water, alcohol and ether, and devoid of aldehydic properties ... 

Trioxane and Tetraoxane. The cycHc symmetrical trimer of formaldehyde, trioxane [110-88-3] is prepared by acid-catalyzed Hquid- or vapor-phase processes (147—151). It is a colorless crystalline soHd that bods at 114.5°C and melts at 61—62°C (17,152). The heats of formation are — 176.9 kJ/mol (—42.28 kcal/mol) from monomeric formaldehyde and —88.7 kJ/mol (—21.19 kcal/mol) from 60% aqueous formaldehyde. It can be produced by continuous distillation of 60% aqueous formaldehyde containing 2—5% sulfuric acid. Trioxane is extracted from the distillate with benzene or methylene chloride and recovered by distillation (153) or crystallization (154). It is mainly used for the production of acetal resins (qv). 

DFT molecular dynamics simulations were used to investigate the kinetics of the chemical reactions that occur during the induction phase of acid-catalyzed polymerization of 205 [97JA7218]. These calculations support the experimental finding that the induction phase is characterized by the protolysis of 205 followed by a rapid decomposition into two formaldehyde molecules plus a methylenic carbocation (Scheme 135). For the second phase of the polymerization process, a reaction of the protonated 1,3,5-trioxane 208 with formaldehyde yielding 1,3,5,7-tetroxane 209 is discussed (Scheme 136). 

The same considerations apply to the explanation which Kern and Jaacks [65] put forward to account for their observation that the polymerization of trioxane by boron fluoride in methylene dichloride not only appears not to require a co-catalyst, but is retarded by water. They write the initiation reaction as... 

Commercial polymers of formaldehyde are also produced using cationic polymerization. The polymer is produced by ring opening of trioxane. Since the polyacetal, POM, is not thermally stable, the hydroxyl groups are esterified (capped) by acetic anhydride (structure 5.22). These polymers are also called poly(methylene oxides). The commercial polymer is a... 

The first ring expansion of a 1,2,4-trioxolane to a 1,2,4-trioxane was observed with (47) where the orientation of the peroxide group was crucial in assisting the triflate to leave (Equation (2)). A 1,2-peroxide shift then follows with loss of silicon giving the methylene substituted 1,2,4-trioxane (48) as the product <91JA8168>. The equatorial triflate does not undergo rearrangement. 

Sodium hydroxide. Sodium cyanide. Bromine, Sulfuric acid Sulfuric acid. Bromine, Sodium cyanide Acetone, Sulfuric acid. Bromine, Methylene chloride Biguanide, Ethanol, Perchloric acid. Ethyl acetate l,3-Dichloro-2-propanol, Trioxane, 1,2-Dichloroethane, Sulfuric acid, Sodium bicarbonate, Dimethylsulfoxide, Sodium azide. Methylene chloride Ammonium nitrate, Nitromethane Ammonium nitrate, Hydrazine Sodium nitrate, Sulfur, Charcoal Potassium nitrate, Sulfur, Charcoal Magnesium powder, Hexachlorethane, Naphthalene... 

Aluminum foil, Iodine powder. Carbon disulfide, 1,4,6,9-Tetrabromodiamantane, Sodium bisulfite. Hydrochloric acid. Methanol, Acetonitrile, Acetone, Sodium hydroxide. Magnesium sulfate. Potassium permanganate. Toluene Methylene chloride, 2-Bromomethanol, Trioxane, Aluminum chloride. Magnesium sulfate, Nitroform, Acetone, Sodium bicarbonate. Hexane, Silver nitrate. Acetonitrile 1,2-Dichloroethane, HexamethyldisUane, Iodine, Cyclohexane, 1,3-Dioxolane, Nitroform, Methylene chloride, Dimethylformamide, Sodium sulfate. Hydrochloric acid. Magnesium sulfate. Nitric acid. Sulfuric acid Sulfuryl chloride. Acetic anhydride. Nitric acid. Sodium bicarbonate. Sodium sulfate Nitric acid. Sulfuric acid, Malonamide Nitric acid. Sulfuric acid, Cyanoacetic acid Sulfuric acid, Acetasalicyclic acid. Potassium nitrate Nitroform, Diethyl ether, 1-Bromo-l-nitroethane, Sodium sulfuate... 

Methylene chloride, 2-Bromoethanol, Trioxane, Aluminum chloride. Magnesium sulfate, Nitroform, Acetone, Sodium bicarbonate. Hexane, Silver nitrate. Acetonitrile... 

Several reviews of early work on topotactic polymerizations and isomeriza-tions are available, and the reader is referred to the summaries of Morawetz [88] and Gougoutas [8] for a more complete account. The earliest study of a topotactic reaction appears to have been the observation, in 1932, of the polymerization of trioxane to poly-oxy-methylene [89]. Similar polymerizations of tetraoxane [90] and of trithiane [91 ] have also been reported to show retention of crystallographic axes from the monomer lattice. Other examples are discussed below. The topo-tacticity of a reaction can be determined solely by x-ray crystallographic analysis at the reactant and product endpoints. Thus a simple classification of a reaction as topotactic tells very little about how the structure of the crystal lattice changed in the course of reaction. 

Polyoxymethylene (POM) plastics are highly crystalline thermoplastics that are obtained by polymerization of formaldehyde and can also be in the form of trioxy-methylene oligomers (trioxane). The world-wide consumption in 1997 was 0.5 x 106 t for car parts and other articles processed by injection moulding. Polyacetals are primarily engineering materials being used to replace metals. 

During the initial polymerization of trioxane with (C4H9)2OBF3 in melt or solution, no solid polymer is formed, and the reaction medium remains clear. Using a high resolution NMR spectroscope, C. S. H. Chen and A. Di Edwardo observed the appearance of soluble linear polyoxy-methylene chains. In the cationic copolymerization of trioxane with 1,3-dioxolane, V. Jaacks found also that a soluble copolymer forms first and turns later into a crystalline copolymer of different composition. Crystallization and polymerization proceed simultaneously in the solid phase. 

To investigate the copolymerization of trioxane with dioxolane and to determine r1 by the excess method, a molar ratio of trioxane to dioxolane of 100 1.8 was used. All polymerizations were run in methylene dichloride at 30°C. with SnCl as initiator. To reduce the influence of formaldehyde production at the beginning of copolymerization, dioxolane was added to the solution of trioxane and initiator only at the end of the induction period—i.e., at the appearance of the first insoluble polyoxy-methylene. After various reaction times polymerizations were terminated by adding tributylamine. Monomer conversions were determined by gas chromatography, the liquid phase being injected directly. When conversions were small, isolation and analysis of the copolymer yielded more accurate results. 

Up to now we have not found reaction conditions permitting exclusive production of insoluble copolymer, which is the desired product in commercial copolymerization of trioxane. Conversion of a large portion of the dioxolane into soluble copolymer could not even be avoided by slow and gradual addition of the comonomer to a homopolymerization run of trioxane in methylene dichloride (9). The same result was obtained in solution copolymerization of trioxane with 8 mole % of 1,3-dioxacycloheptane (dioxepane), and even 1,3-dioxane—which is not homopolymerizable and is a very sluggish comonomer—formed a soluble copolymer in the initial phase of copolymerization (trioxane 2.5M 1,3-dioxane 0.31M SnCb 0.025M in methylene dichloride at 30°C.). 

The soluble copolymer was isolated, dried, and added to a homopolymerization run of trioxane in methylene dichloride. After a few minutes at 30°C. appreciable amounts of monomeric dioxolane were identified by gas chromatography. 

Dioxolane was also formed in the absence of trioxane when the soluble copolymer was simply dissolved in a 0.03M solution of SnCl4 in methylene dichloride at 30°C. (conditions similar to those of the copolymerization in Figure 3). Within one hour half of the soluble copolymer was depolymerized under formation of dioxolane monomer and formaldehyde. 

The polymerizability of a monomer is also influenced by the physical state of the polymerization. For example, crystallization of poly(oxy methylene) provides the driving force for trioxane polymerization. In this case, propagation occurs at active sites on the crystal lattice rather than in solution, and AGP includes the change in free energy of the phase transition as well as that of the solution polymerization [Eq. (19)]. 

The polycyclic 1,2,4-trioxane 40 is formed when H2O2 is added to the hDA dimer of methylene cyclohexanone <03OBC2859>. 

RCRA WASTE NUMBER LT 82 TRIACETALDEHYDE (FRENCH) 2,4,6-TRIMETHYL-l,3,5-TRIOXAAN PUTCH) 2,4,6-TRIMETHYL-s-TRIOXANE 2,4,6-TRI vIETHYL- ,3,5-TRIOXANE s-TRIMETHYLTRIOXY-METHYLENE 2,4,6-TRIMETIL-l,3,5-TRIOSSANO (ITALIAN)... 

The BF3/l,3j5-trioxane system is one of the few so far discovered in which there is a possibility that monomeric units add at the cationic end of a macrozwitterion. Fortunately, the cation seems to be stable in the presence of its counter anion. As a simple model system with which to study cationic propagation through zwitterion intermediates it is marred by its equilibrium nature and the insolubility of the polymer. Whilst kinetic termination seems to be absent, the authors report transfer to the solvent methylene chloride. Such a reaction would introduce non-zwitterionic chains. 

This oxonium ion may in some cases react in its resonance form, the carbonium ion. The propagation step could be by electrophilic attack of the electrophilic carbonyl atom of the methylene group on the oxygen atom of the carbonyl group of the highly polar formaldehyde. This mechanism is similar to that advanced for the polymerization of trioxane or tetrahydrofuran. A further refinement of the mechanism takes into account the likely possibility that this oxonium ion... 

Fig. 4. Dependence of the maximum polymerization rate of trioxane in methylene dichloride on the initial monomer concentration. (Pdiss dissolved polymer, Psoh

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