Solutions, formaldehyde Solvent properties

Trioxane is a mast unusual chemical. It is an excellent solvent for many classes of moteriols. Concentrated aqueous solutions of trioxane have solvent properties which are not possessed by trioxane itself. Molten trioxane dissolves numerous organic compounds, such as naphthalene, urea, camphor, dichlorobenzene, etc. It Is stable in alkaline or neutral solutions, yet it is depolymerized ta formaldehyde by small amounts of strong acid or acid-farming materials, and the rate of depolymerization can be readily controlled. 

Phenol-formaldehyde is a thermosetting polymer and has a number of desirable properties for a polymer, it is very heat resistant and hard is less brittle than many of the ceramic materials is very stable and unreactive with most common solutions and solvents and doesn t easily chip, fade, or discolor. Furthermore, it is a relatively inexpensive material, and modem phenolics can be produced having a large variety of colors. The elastic characteristics of this polymer are very similar to those of ivory, and when phenolic bilhard baUs coDide, they make the same chcking sound as ivory baUs. Other uses of this important polymeric material are given in Table 15.3. 

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 ... 

To a solution of scandium fluoride (0.03 mmol 10 mol%) in THF-H2O (0.22 mL) was added 36% aqueous solution of formaldehyde (1 1.5 mmol 5 equiv.) and dimethylsilyl enolate (2 0.3 mmol). The mixture was stirred for 40 h at room temperature to complete the reaction. The mixture was then diluted with water (10 mL), and the aqueous layer was extracted with dichloromethane (3 x 20 mL). The combined organic extracts were washed with brine, and dried over anhyd. sodium sulfate. After filtration, the solvent was removed in vacuo. The crude residue was purified by preparative TLC (elution with n-hexane-EtOAc) to furnish p-hydroxy ketone 3 with good yield (71-93%). All the compounds were characterized from comparison of their physical and spectral properties with those reported for authentic samples in literature. 

Properties. Gamma-polyox miethylene is a colorless cn stalline product which decompt es on heating in the temperature range 160-210 C. The exact temperature of decomposition depends on the method of preparation and purification. It melts to a clear liquid at approximately 160-180°C. On % aporization, it depolymerizes to monomeric formaldehyde gas. The pohmer does not smell of formaldehyde and is insoluble in water and organic solvents. It is not affected by dilute alkalies, but dissolves with hydrolysis in acidic solutions when heat is appHed. 

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