1,3,5,7-Tetraoxane FORMALDEHYDE

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). 

A practical synthesis has been claimed for the cycHc tetramer of formaldehyde, 1,3,5,7-tetraoxane [293-30-17, which has a boiling point of 175°C and a melting point of 112°C (155). It has found some use in textde treatment in Japan. 

Oxidative processes can also be used to prepare DMF. For example, it can be produced from tetraoxane (a source of formaldehyde (qv)), oxygen, and dimethylamine over Pd—AI2O2 (24) or from trimethylamine and oxygen ia the presence of a metal haUde catalyst (25). 

NMR, like other instrumental techniques, has limiting factors which preclude complete insight into changes occurring during a chemical reaction. One of the major disadvantages is its limiting sensitivity which precludes detection of chemical moieties at low concentrations. The formation of formaldehyde and/or tetraoxane reported for the homopolymerizations (I, 2), and 1,3-dioxolane for the copolymerization could not be verified. 

Formation of polymerizable by-products (formaldehyde, 1,3,5,7-tetraoxane, 1,3,5,7,9-pentaoxane, and other cycles). 

Valuable information on the mechanism of the process and on the confirmation of the formulated assumptions was obtained by analyzing the low-molecular-weight by-products of trioxane polymerization reaction 1,3,5,7-tetraoxane and formaldehyde. Theoretical analysis has shown that, depending on the state of active centers (surface or dissolved) and the length of the dissolved portion of the polymer chain, the steady-state concentration of 1,3,5,7-tetraoxane and formaldehyde changes. A comparison between experimental and theoretical data has shown that at monomer... 

Formaldehyde, trioxane, 1,3,5,7-tetraoxane, and dissolved oligomer chains (with a small degree of polymerization) are here in equilibrium. Therefore, the steady-state concentrations of formaldehyde and 1,3,5,7-tetraoxane depend on trioxane concen-... 

One of the objectives of the investigators during their research into the thermodynamic characteristics of the formaldehyde — trioxane — 1,3,5,7-tetraoxane — —... 

Several papers57"59 were devoted to investigating a complex process such as the cationic copolymerization of monomeric formaldehyde with dioxolane in the gas, liquid, and gas-liquid phases. It is known that polyacetal resins are industrially produced by copolymerizing cyclic acetals (trioxane, 1,3,5,7-tetraoxane), or by anionic homopolymerization of monomeric formaldehyde with subsequent modification of end groups. 

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