Uses of formaldehyde

Amino and Phenolic Resins. The largest use of formaldehyde is in the manufacture of urea—formaldehyde, phenol—formaldehyde, and melamine—formaldehyde resins, accounting for over one-half (51%) of the total demand (115). These resins find use as adhesives for binding wood products that comprise particle board, fiber board, and plywood. Plywood is the largest market for phenol—formaldehyde resins particle board is the largest for urea—formaldehyde resins. Under certain conditions, urea—formaldehyde resins may release formaldehyde that has been alleged to create health or environmental problems (see Amino RESINS AND PLASTICS). 

Another method of removing mercury compounds from aqueous solution is to treat them with water-soluble reducing agents, thus hberating metallic mercury (26). The use of formaldehyde (qv) at a pH of 10—12 also is recommended. 

Uses of Formaldehyde. Formaldehyde is the simplest and most reactive aldehyde. Condensation polymerization of formaldehyde with phenol, urea, or melamine produces phenol-formaldehyde, urea formaldehyde, and melamine formaldehyde resins, respectively. These are important glues used in producing particle hoard and plywood. 

Phenol-formaldehyde resins using prepolymers such as novolaks and resols are widely used in industrial fields. These resins show excellent toughness and thermal-resistant properties, but the general concern over the toxicity of formaldehyde has resulted in limitations on their preparation and use. Therefore, an alternative process for the synthesis of phenolic polymers avoiding the use of formaldehyde is strongly desired. 

Recently, Vasilescu et al. demonstrated the use of formaldehyde to preserve protein interactions in vivo followed by immunoaffinity purification of a targeted complex, cross-link reversal via heating at 95°C, separation by SDS-PAGE, and identification of bands by LC-MS/MS.7 Tagwerker et al. utilized formaldehyde cross-linking in conjunction with a novel tag-based affinity purification method.36... 

The following protocol is a generalized method that summarizes the publications on the use of formaldehyde for capturing interaction proteins. The ranges indicated for concentrations of reactants and time of the reaction need to be optimized for each protein interaction studied. 

As Equation (54) shows, N-substituted amidoximes 306 will also react with either formaldehyde or acetaldehyde to give the 4,5-dihydro-l,2,4-oxadiazoles 307. Acetaldehyde required the presence of acetic acid, whereas the use of formaldehyde allowed the reaction to proceed in the absence of acid <1998EJM715>. 

Preparation of 2-unsubstituted products by this method would require the use of formaldehyde as the aldehyde component, which gives low yields. However, the use of glyoxylic acid, either as the free acid or bound to macroporous polystyrene carbonate, results in satisfactory formation of the 2-unsubstituted products through an in situ decarboxylation <2004OL4989>. The use of a nonpolar solvent (toluene) has been reported to reduce the formation of side products in this type of reaction <2006TL947>. 

The formaldehyde process is an air oxidation of methanol, CH3OH, which has water as a by-product. Formaldehyde is a gas at room temperature, but is usually handled either as a water solution called formalin or as polymers called paraformaldehyde and trioxane. Both are readily converted back ro formaldehyde. Some uses of formaldehyde are the manufacture of polymer resins and as a germicide. 

In 2008, the same group employed chiral dicarboxylic acid (R)-5 (5 mol%, R = 4- Bu-2,6-Me2-CgHj) as the catalyst in the asymmetric addition of aldehyde N,N-dialkylhydrazones 81 to aromatic iV-Boc-imines 11 in the presence of 4 A molecular sieves to provide a-amino hydrazones 176, valuable precursors of a-amino ketones, in good yields with excellent enantioselectivities (35-89%, 84-99% ee) (Scheme 74) [93], Aldehyde hydrazones are known as a class of acyl anion equivalents due to their aza-enamine structure. Their application in the field of asymmetric catalysis has been limited to the use of formaldehyde hydrazones (Scheme 30). Remarkably, the dicarboxylic acid-catalyzed method applied not only to formaldehyde hydrazone 81a (R = H) but also allowed for the use of various aryl-aldehyde hydrazones 81b (R = Ar) under shghtly modified conditions. Prior to this... 

Table 12.3 summarizes the uses of formaldehyde. Two important thermosetting plastics, urea- and phenol-copolymers, take nearly one half the formaldehyde manufactured. Urea-formaldehyde resins are used in particleboard, phenol-formaldehyde resins in plywood. 1,4-Butanediol is made for some polyesters and is an example of acetylene chemistry that has not yet been replaced. Tetrahydrofiiran (THF) is a common solvent that is made by dehydration of 1,4-butanediol. 

All manipulations should be carried out in a wel1-ventilated hood. The preparation requires the use of formaldehyde solution, and gives rise to ethyl acrylate as a secondary product, the amount of which increases if the addition of the carbonate solution is too rapid and the temperature rises to 45°C. 

Uses of Formaldehyde. Consumption in the US increased from about 8.5 million pounds in 1914 to 50 0 million pounds in 1943... 

The use of formaldehyde results in a pyrylium salt unsubstituted at C-4 (66BSF2959), whilst a neat variation in the ketone component enabled some 4-aryl-2,6-diethoxycarbonyl-pyrylium salts to be synthesized (81S959). 

A number of MCRs having enolate-derived nucleophilic components were subsequently discovered (Scheme 7.3), including the Hantzsch dihydropyridine synthesis [13], the Biginelli reaction [14, 15] and the Mannich reaction [16-20], An added complication in many of these MCRs is the potential irreversible addition of the nucleophile to the carbonyl component, leading to carbonyl addition products. Such MCRs, however, become feasible by the appropriate selection of components that do not favor such alternative transformations. For example, the use of formaldehyde is more effective in the Mannich reaction, because its greater reactivity towards the amine prevents its undesired reaction with the enolate component. 

Another common gas that appears on the list of potential teratogens is formaldehyde. Since it is normally used as a 40% aqueous solution ("formalin"), it is listed in Table 2 with the organic liquids. Only four of the twenty lab manuals use formaldehyde one in a clock reaction, two to test for the presence of the aldehyde group, and the other to make a polymer of the phenol-formaldehyde type. In none of these is the use of formaldehyde essential. There are other simple clock reactions, there are other less hazardous aldehydes, and there are other polymerization reactions that would be more suitable for an introductory chemistry course. 

Urushi, a natural lacquer, has been used on the ISFET surface [89] to make, amongst other devices, a chloride sensor. The natural lacquer has a long curing time (10 days) but this can be shortened to 2-3 days with the use of formaldehyde as a crosslinking agent [90] and has been successfully used in the production of a nitrate sensor. 

Step 3 The reaction of a tertiary Grignard reagent with a hindered ketone may result in reduction and/or enolization of the ketone. However, in the present example, the use of formaldehyde (an excellent electrophile) circumvents these side reactions. 

The acid-catalysed reaction of resorcinol with aldehydes leads to cyclic tetra-mers which are grouped in the class of resorc[4]arenes (exo-calixarenes).3 This reaction is quite general with respect to the aldehyde and to the starting resorcinol, which can bear several substituents in the 2-position.15 Niederl and Hogberg showed in a typical example, the synthetic procedure by which an ethanol solution of resorcinol, acetaldehyde and 37% hydrochloric acid maintained at 80 °C for 16 h, afforded 75% of the all cis C-methylresorc[4]arene. A shorter reaction time leads to the kinetic stereoisomer (trans,cis,trans,cis).16 This procedure is general for many aldehydes (Scheme 7.4), but the use of formaldehyde is limited to some special cases.17... 

The use of formaldehyde-free adhesive resins from whey and whey byproducts for manufacturing construction-quality boards could resolve these problems simultaneously. The demand for formaldehyde-based thermosetting adhesive resins in the United States was estimated to be 1.9 billion pounds in 1983 (5). The anticipated requirement for resins and the potential availability of raw materials from whey are a fortuitous combination. 

Table 1.29 lists the main uses of formaldehyde in Western Europe, the United Slates and Japan in 1984, as well as the production, capacities and consumption in these three geographic areas. Capacities are abo given for 1986. 

The R group may be aliphatic or aromatic. The use of formaldehyde in the initial condensation gives compounds without the 5 alkyl group. ... 

The organic ground on which these observations fell was fertile. The reducing power of aldehydes was well known, for example the use of formaldehyde (together with zinc dithionite) in the dye industry. ... 

In view of the environmental concern about the use of formaldehyde, which is a known carcinogen, attempts have been made to develop new bath formulations using other reducing agents, e.g., hydrophosphite [148-152] or glyoxylic acid [153, 154]. The interested reader is referred to the original papers. 

The need to re-evaluate the rationale underlying the use of formaldehyde, formocresol, and paraformaldehyde in dentistry has been stressed, since the clinical use and delivery of these products are considered to be arbitrary and unscientific (37). 

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