Formaldehyde sources

Another significant use of 3-methylphenol is in the production of herbicides and insecticides. 2-/ f2 -Butyl-5-methylphenol is converted to the dinitro acetate derivative, 2-/ f2 -butyl-5-methyl-4,6-dinitrophenyl acetate [2487-01 -6] which is used as both a pre- and postemergent herbicide to control broad leaf weeds (42). Carbamate derivatives of 3-methylphenol based compounds are used as insecticides. The condensation of 3-methylphenol with formaldehyde yields a curable phenoHc resin. Since 3-methylphenol is trifunctional with respect to its reaction with formaldehyde, it is possible to form a thermosetting resin by the reaction of a prepolymer with paraformaldehyde or other suitable formaldehyde sources. 3-Methylphenol is also used in the production of fragrances and flavors. It is reduced with hydrogen under nickel catalysis and the corresponding esters are used as synthetic musk (see Table 3). 

Dioxanes can be efficiently synthesized from styrenes using formalin as the formaldehyde source (Prins reaction) with triflic acid as catalyst717 [Eq. (5.267)]. 

A procedure based on condensation with phenol and paraform (used as formaldehyde source) was developed to convert spent UNEX solvent (CCD, PEG-400, Ph2-CMPO, and FS-13) into a solid infusible resin for disposal. The resulting material is insoluble in aqueous alkali and acidic solutions and organic solvents. Incorporation of FS-13 in the cross-linked polymer was confirmed by physicochemical methods. Resistance of the cured resin to high temperatures was proven by thermogravimetry... 

While concrete and plaster products are essentially inorganic products, additives used in forming or manufacturing these products may act as VOC and formaldehyde sources, though little has been published on their emissions. 

The tannin side (component A) was made alkaline by addition of NaOH at various levels (Table I). No formaldehyde source was added to the tannin... 

Reaction Variables. An excess of paraformaldehyde was necessary (15 to 35 mole % excess was used) when the prepolymers were built up in solution. An excess evidently was not necessary when the prepolymers were built up in the solid phase. In experiments with tetramethylcyclobutanediol, a polymer with an inherent viscosity of 1.2 was obtained when the diol was present in 5 mole % excess, but the polymer was brown. When the paraformaldehyde was in excess, the amount was not critical, but it was necessary to use a minimum of about 10 mole % excess in order to obtain white polymers. Polyformals with inherent viscosities of 0.5 or greater were obtained when the molar excess of paraformaldehyde ranged from 2 to 40%. The highest inherent viscosities (above 1.0) were obtained when the excess was about 10 mole %. When trioxane was used as the formaldehyde source instead of paraformaldehyde, reaction did not take place (no water was obtained). 

B.B. Snider and FI. Yamamoto respectively developed formaldehyde-organoaluminum complex as formaldehyde source in several reactions, (a) Snider, B.B. Rodini, D.J. Kirk, T.C. Cordova. R. 

Often, the additive is a formaldehyde source such as hexamethylenetetramine (HMTA). On the other hand, a resole is capable of forming a network structure by the application of heat. 

Novolacs are thermoplastic polymers that require the addition of a formaldehyde source to enable further curing and the formation of insoluble and infusible products. 

Removing formaldehyde sources from the house will also reduce the risk of exposure. Since formaldehyde is found in tobacco smoke, not smoking or smoking outside will reduce exposure to formaldehyde. Unvented heaters, such as portable kerosene heaters, also produce formaldehyde. If you do not use these heaters in your home or shop, you help to prevent the build up of formaldehyde indoors. 

This vapor acts as a driving force for formaldehyde diffusion from the wood cel I towards the product surface, and for emission from the finished wood product. An internal vapor pressure of 20 Torr would approximately correspond to a formaj ehyde air concentration of about 1 ppm at 25 t, a load factor of I m and a ventilation rate of 1 ach. However, as emission continues and depletes the methylene glycol concentration in the wood moisture, the dissociation of hemiacetals will set in and add to the formaldehyde source. The bottleneck in the formaldehyde transport will be diffusion through the product towards the product surface. This process depends on the permeability of the product which, in turn, depends on diffusion... 

Godish, T, Kanyer, B. Formaldehyde source interaction studies. For. Prod. J. 1985,35,4,13-17... 

The CEA 555 continuous monitor(17) is used for real-time monitoring of chamber and actual field survey formaldehyde determinations. The monitor is a useful instrument in field surveys because it is one method that provides real time formaldehyde measurements which is useful in tracing and iden tifying usually high formaldehyde sources. The monitor s analytical method is based on the modified Schiff procedure developed by Lyles, Dowling and Blanchard (18). Formaldehyde is absorbed in a sodium tetrachloromercurate solution that contains a fixed quantity of sodium sulfite. Acid bleached pararosaniline is added, and the intensity of the resultant dye is measured at 500 nm. Both formaldehyde in air and liquid standards can be analyzed. 

Reducing formaldehyde emission below 0.1-0.2 ppm is currently unrealistic, because ambient air levels may be higher due to other formaldehyde sources. 

Snider BB and Yamamoto K respectively developed formaldehyde-organoaluminum complex as formaldehyde source in several reactions (a) Snider BB, Rodini DJ, Kirk TC, Cordova R (1982) J Am Chem Soc 104 555 (b) Snider BB (1989) In Schinzer D (ed) Selectivities in Lewis acid promoted reactions. Kluwer Academic Publishers, London, pp 147-167 (c) Maruoka K, Conception AB, Hirayama N, Yamamoto H (1990) J Am Chem Soc 112 7422 (d) Maruoka K, Concepcion AB, Murase N, Oishi M, Yamamoto H (1993) J Am Chem Soc 115 3943... 

Preparation of Resins. Paraformaldehyde may be used in place of formalin as a formaldehyde source. This reduces the processing time but makes control of the exothermic reaction more difficult. Furfural and... 

Trioxane has been employed as the formaldehyde source for the synthesis of calixarene derivatives during the cyclization step <1991JOC5527, 2002T2239,2002PSA1293>. Also, the Mannich reaction of dioxazasilacyclo-octane with 1,3,5-trioxane as the formaldehyde source has been reported <1989ZOB483>. 

Methyl alcohol formaldehyde scavenger Aminoethyl propanediol formaldehyde scavenger, curing phenolics Tris (hydroxymethyl) aminomethane formaldehyde source... 

Carbonylation of formaldehyde with carbon monoxide was also performed on various protonated zeolites such as H-ZSM-5, silicalite, H-MOR, H-Y, H-BEA, and MCM-41 (63). l,3-Dioxolan-4-one (l,3-DOX-4) is produced on Br0nsted acid sites of zeolite. H-ZSM-5, H-Y, and H-BEA zeolites with the three-dimensional channel system show the high activity for the formation of l,3-DOX-4. The reaction is carried out under batch conditions in dry methylene chloride solution, and trioxane is used as the formaldehyde source, at 40-180°C, 150-570 atm CO... 

In 2010, Morimoto and coworkers showed that a combination of two Rh catalysts [Rh(BIPHEP), Rh(Nixantphos)] can be beneficial, one for the decomposition of formaldehyde and the second for the hydroformylation of olefins (Scheme 3.5) [16]. With this system, aldehydes could be produced with a yield of 95% and a ratio of l/b = 97 3 independent on the formaldehyde source (formalin, paraformaldehyde). 

Chemical reaction dynamics of methanol oxidation to formaldehyde.Top elongation of one C-H bond (white arrow) and subsequent breaking. Bottom stabilization of the intermediate by hydrogen bonds and formation of formaldehyde. (Source Hartnig and Spohr 2005). 

Lewis acid catalysis is one of the most useful methods in modern organic synthesis. However, many of the common Lewis acids are highly water-labile and have been used in organic synthesis under strictly anhydrous conditions. Contrary to this, it was found that lanthanide triflates catalyzed aldol reactions of formaldehyde (Scheme 3.6). Formaldehyde is one of the most highly reactive Cl electrophiles. In this reaction, not gaseous formaldehyde but a commercially available aqueous solution was used as the formaldehyde source. This invaluable find introduced the concept of Lewis acid catalysis in aqueous media to many chemists. Later, it was also reported that other aldol reactions, with a variety of aldehydes and silyl enol ethers, as well as allylation reactions, proceeded smoothly in aqueous media to afford the desired compounds in high yields. ... 

CAUTION Toxicity) Phenols, formaldehyde, and other aldehydes are toxic and should be handled with adequate ventilation and skin protection [17]. Where possible the use of hydrogen chloride in the presence of formaldehyde or formaldehyde sources (hexamethylenetetramine and the like) should be avoided. Recent reports have indicated that formaldehyde and hydrogen chloride spontaneously react to give the known carcinogen 6w(chloromethyl) ether. 

Figure 17.2. Raman spectrum of bulk Mo03/Fe2(Mo04)3 catalysts commercially employed for methanol oxidation to formaldehyde. Source K. Routray and 1. Wachs.

Thermoset materials can be made from phenolic resins themselves, requiring an acid or base catalyst or additional formaldehyde source, or in combination with various other resins. An exhaustive list is not given here, but examples of combinations with all the resin types in the next sections are known (especially amino resins. Section 16.3 epoxy resins. Section 16.4 alkyd resins, Section 16.5 and saturated polyester resins. Section 16.6). 

Curing of novolacs requires addition of extra formaldehyde mosdy HMTA, typically 8-15%, is used as a solid formaldehyde source. 

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