Formaldehyde boiling point

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. 

Formaldehyde is a gas with a boiling point of -21 °C. It is usually supplied as a stabilised aqueous solution ( 40% formaldehyde) known as formalin. When formalin is used as the source of the aldehyde, impurities present generally include water, methanol, formic acid, methylal, methyl formate and carbon dioxide. The first three of these impurities interfere with polymerisation reactions and need to be removed as much as possible. In commercial polymerisation the low polymers trioxane and paraformaldehyde are convenient sources of formaldehyde since they can be obtained in a greater state of purity. 

When catalyzed by acids, low molecular weight aldehydes add to each other to give cyclic acetals, the most common product being the trimer. The cyclic trimer of formaldehyde is called trioxane, and that of acetaldehyde is known as paraldehyde. Under certain conditions, it is possible to get tetramers or dimers. Aldehydes can also polymerize to linear polymers, but here a small amount of water is required to form hemiacetal groups at the ends of the chains. The linear polymer formed from formaldehyde is called paraformaldehyde. Since trimers and polymers of aldehydes are acetals, they are stable to bases but can be hydrolyzed by acids. Because formaldehyde and acetaldehyde have low boiling points, it is often convenient to use them in the form of their trimers or polymers. 

It is reported that an industrial explosion was initiated by charging potassium hydroxide in place of potassium carbonate to the chloro-nitro compound in the sulfoxide [1], Dry potassium carbonate is a useful base for nucleophilic displacement of chlorine in such systems, reaction being controlled by addition of the nucleophile. The carbonate is not soluble in DMSO and possesses no significant nucleophilic activity itself. Hydroxides have, to create phenoxide salts as the first product. These are better nucleophiles than their progenitor, and also base-destabilised nitro compounds. Result heat and probable loss of control. As it nears its boiling point DMSO also becomes susceptible to exothermic breakdown, initially to methanethiol and formaldehyde. Methanethiolate is an even better nucleophile than a phenoxide and also a fairly proficient reducer of nitro-groups, while formaldehyde condenses with phenols under base catalysis in a reaction which has itself caused many an industrial runaway and explosion. There is thus a choice of routes to disaster. Industrial scale nucleophilic substitution on chloro-nitroaromatics has previously demonstrated considerable hazard in presence of water or hydroxide, even in solvents not themselves prone to exothermic decomposition [2],... 

Racemic 4-(4-fluorophenyl)-l-methyl-l,2,3,6-tetrahydropyridine (50 g) was dissolved in a mixture of 21.6 ml of concentrated sulfuric acid and 50 ml of water. To the solution were added 25 ml of concentrated hydrochloric acid and 22.4 ml of 37% formaldehyde solution. The mixture was refluxed for 5 h, cooled, and 125 ml of concentrated ammonia were added. The mixture was extracted with 50 ml of toluene. Drying of the toluene solution and distillation gave 38 g of 4-(4-fluorophenyl)-3-hydroxymethyl-l-methyl-l,2,3,6-tetrahydropyridine with boiling point 110°-120°C at 0.1 mm Hg. 

Formaldehyde (methanal, melting point -92°C, boiling point -21°C) is produced solely from methanol by using a silver catalyst (Fig. 1) or a metal oxide catalyst (Fig. 2). Either process can be air oxidation or simple dehydrogenation. 

In the pure form, formaldehyde in the pure form is a gas with a boiling point of -21°C but is unstable and readily trimerizes to trioxane or polymerizes to paraformaldehyde. Formaldehyde is stable only in water solution, commonly 37 to 56% formaldehyde by weight and often with methanol (3 to 15%) present as a stabilizer. 

Propargyl alcohol (2-propyn-l-ol, boiling point 114°C) is a colorless volatile liquid with an unpleasant odor that is the only commercially available acetylenic primary alcohol. It is miscible with water and with many organic solvents. The commercial material is specified as 97% minimum purity, determined by gas chromatography or acetylation. Moisture is specified at 0.05% maximum (Karl-Fischer titration). Formaldehyde content is determined by bisulfite titration. 

Pyridine (boiling point 115.5°C, density 0.9819) is manufactured by reacting formaldehyde, acetaldehyde, and ammonia at 350 to 550°C in the presence of a silica-alumina catalyst (Si02-Al203), and the principal products are pyridine (1) and 3-picoline (3-methyl pyridine). 

Carbohydrates are especially unstable, even at temperatures well below the boiling point of water. This instability arises from the fact that they contain a C=0 unit. Because of this instability, some have proposed that carbohydrates could not have been part of genetic molecules in early life, as they are in modem life, at least until advanced metabolic repair, and sequestration became available to manage their reactivity. Indeed, until recently, no nonbiological process was well established that would yield carbohydrates under plausibly prebiotic conditions and in sufficient concentrations before the carbohydrates were then destroyed under the same conditions in which they were formed.1 The simplest carbohydrate that has been observed in the interstellar medium is formaldehyde the most complex, glycolaldehyde (Figure 2.7). 

The polyvinyl alcohol is soluble in hot water, and the solution is wet-spun into a coagulating bath consisting of a concentrated solution of sodium sulfate. The fibers are heat-treated to provide temporary stability so that they may be converted to the formal derivative by treatment with an aqueous solution of formaldehyde and sulfuric acid. This final product resists hydrolysis up to the boiling point of water. It seems reasonable to assume that it contains hemiacetal groups and some unreacted hydroxyls on the polymer chain as... 

All dichloromethane examined showed 2-14 ppm of formaldehyde contamination. Several clean up methods were applied to remove formaldehyde such as washing with sodium bisulfite, treatment with active charcoal of Porapak Q porous polymer without success. Trace levels of formaldehyde in solvents may be impossible to remove. Therefore, chloroform was used as the solvent for formaldehyde analysis in further experiments. The amount of contaminant obtained from a blank solvent was always subtracted from the values of actual results. Dichloromethane was, however, used for methyl glyoxal analysis. The extraction efficiency of chloroform and dichloromethane was almost identical. Dichloromethane was easier to use for a liquid-liquid continuous extraction than chloroform because of its lower boiling point. 

Trioxane is a stable, cyclic trimer of formaldehyde. It has chloroform like odor, and is a crystalline solid with a melting point of 64 Celsius, and a boiling point of 114.5 Celsius. It sublimes readily and is very soluble in water, acetone, alcohol, ether, and chlorinated hydrocarbon solvents. Trioxane forms an azeotrope when distilled with water, boiling at 91 Celsius, and containing 70% trioxane by weight. Trioxane slowly depoly merizes when treated with acids, and in the absence of water, it breaks down to monomeric formaldehyde when treated with acids. Trioxane is inert to alkalies. It is commercially available. 

In contrast to aliphatic alcohols, which are mostly less acidic than phenol, phenol forms salts with aqueous alkali hydroxide solutions. At room temperature, phenol can be liberated from the salts even with carbon dioxide. At temperatures near the boiling point of phenol, it can displace carboxylic acids, e.g. acetic acid, from their salts, and then phenolates are formed. The contribution of ortho- and -quinonoid resonance structures allows electrophilic substitution reactions such as chlorination, sulphonation, nitration, nitrosation and mercuration. The introduction of two or three nitro groups into the benzene ring can only be achieved indirectly because of the sensitivity of phenol towards oxidation. Nitrosation in the para position can be carried out even at ice bath temperature. Phenol readily reacts with carbonyl compounds in the presence of acid or basic catalysts. Formaldehyde reacts with phenol to yield hydroxybenzyl alcohols, and synthetic resins on further reaction. Reaction of acetone with phenol yields bisphenol A [2,2-bis(4-hydroxyphenyl)propane]. 

There have been contradictory reports about the reaction of wood with formaldehyde from UF-resins. At room temperature, and up to the boiling point of water, wood absorbs only very little formaldehyde. Thus, gine chips treated with 35 wt% formaldehyde solution for 30 min at 160°C retain less than 0.01 wt% formaldehyde (3). Forest products scientists generally assume that UF resins do not bond to wood (4). However, at higher temperatures, wood absorbs formaldehyde and irreversibly changes its physical properties. Thus, after 15 hrs of exposure at 120 C, 7 wt% formaldehyde is retained by solid oak and causes a 50% reduction in swelling (5-8). Since wood cellulose is... 

An environmental application of liquid extraction is the removal of trace organics from water. Examples are the separation of acetic acid-water mixtures and removal of solvents, insecticides, pesticides, etc., from water. It can also be applied to the separation of liquids with close boiling points or those that form azeotropes, such that distillation is not useful. In addition, zero- or low-volatility compounds, such as metals and organometallic derivatives, can be separated by liquid extraction as can mixtures of water-hydrogen bonded compounds, such as formaldehyde. Solid extraction (leaching) can be used to remove organics or heavy metals from contaminated soils, sludges or contaminated equipment. 

An additional mechanism for non-ideal liquid-phase solutions is hydrogen bonding. An example is formaldehyde that has a boiling point (-19 °C) much lower than that of water. But, it hydrogen bonds very strongly with water so it is difficult to remove by stripping. LLE is an effective approach for this separation. 

However, its boiling point (64.7 °C) is lower than that of water, and so usage of methyl alcohol has decreased in this area. Methyl alcohol can be dissolved in all proportions in water and organic solvents and can also dissolve fats and resins. Methyl alcohol can be converted into formaldehyde and this is the raw material for industrial products such as plastics, paints and solvents. 

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