SUBJECTS formaldehyde

Foams prepared from phenol—formaldehyde and urea—formaldehyde resins are the only commercial foams that are significantly affected by water (22). Polyurethane foams exhibit a deterioration of properties when subjected to a combination of light, moisture, and heat aging polyester-based foam shows much less hydrolytic stabUity than polyether-based foam (50,199). 

Phenohc resins are produced by the condensation of phenol or a substituted phenol, such as cresol, with formaldehyde. These low cost resins have been produced commercially for more than 100 years and in the 1990s are produced by more than 40 companies in the United States. They are employed as adhesives in the plywood industry and in numerous under-the-hood appHcations in the automotive industry. Because of the cycHc nature of the automotive and home building industry, the consumption of phenol for the production of phenohc resins is subject to cycHc swings greater than that of the economy as a whole. 

Acrolein (CH2=CHCHO) can be substituted for formaldehyde and acetaldehyde in the above reaction to give similar results, but the proportion of (3) is higher than when acetaldehyde and formaldehyde are fed separately. Acrolein may be formed as one of the first steps to pyridine (1) and P-picoline (3) formation. There are many variations on the vapor-phase synthesis of pyridine itself. These variations are the subject of many patents in the field. 

If the product of the first stage, which in practice usually also contains unreacted urea and formaldehyde, is then subjected to acid conditions at elevated temperatures the following sequence of events is observed during the second stage ... 

To produce a moulding composition, aniline is first treated with hydrochloric acid to produce water-soluble aniline hydrochloride. The aniline hydrochloride solution is then run into a large wooden vat and formaldehyde solution is run in at a slow but uniform rate, the whole mix being subject to continuous agitation. Reaction occurs immediately to give a deep orange-red product. The resin is still a water-soluble material and so it is fed into a 10% caustic soda solution to react with the hydrochloride, thus releasing the resin as a creamy yellow slurry. The slurry is washed with a counter-current of fresh water, dried and ball-milled. 

Prior to 1890, formaldehyde was not commercially available [2]. Thus the first phenol-formaldehyde resins were made using formaldehyde equivalents such as methylene diacetate or methylal [2,20]. The first true phenol-formaldehyde resin was made by Kleeberg at the direction of Emil Fisher in 1891 [2,21]. Saliginen (o-hydroxymethyl phenol) was recognized as a condensation product of phenol and formaldehyde in 1894 and was the subject of United States patents in 1894 and 1896 [22,23]. 

Further, isoxazole derivatives were subjected to two related reactions. 3,5-Dimethylisoxazole was found to react in the presence of dry hydrogen chloride with aromatic aldehydes (chlorobenzylation, 72- 71),and with formaldehyde in the presence of sulfuric acid it undergoes hydroxymethylation (72- 73). ... 

Exactly this problem was the subject of synthetic experiments carried out by J. Oro et al. (1984), which were intended to clarify the possible formation of these condensation agents. They used simple compounds, such as formaldehyde, acetaldehyde, glyoxal and ammonia as starting materials, and were able to synthesize imidazole as well as its 2- and 4-methyl derivatives. 

Penicillamine (50 mg) was mixed with 50 mg of formaldehyde, 50 pL of concentrated HC1, and 2.5 mL of propan-2-ol, and the solution heated at 60 °C for 2 h. An aliquot of the reaction mixture was subjected to TLC on a Chiralplate (Macherey-Nagel) with a mobile phase of methanol-H20-aeetonitrile (1 1 4). Detection was made using 0.1% ninhydrin reagent, and the limit of detection was approximately 0.5%. Good separation of (d)- and (L)-penicillamine was achieved. 

Fathalla et al. reported that some [l,2,4]triazolo[4,3- ]quinazoles can be subjected to various transformations involving the triazole nitrogen atom <2000MOL1210>. Thus, treatment of 186 with formaldehyde and pyrrolidine... 

Synthesis of a C(8)-C(18) segment of the larger fragment of lb using the same basic strategy is depicted in Scheme 25. Here, hydroxy ketone 176 was subjected to syn-selective (dr of crude product=90 10) reductive amination [42] with sodium cyanoborohydride and benzylamine followed by tetrahydro-oxazine formation using aqueous formaldehyde. The resulting heterocycle 182 was then converted to unsaturated ester 184 by successive desilylation, oxidation, and entirely (Z)-selective Horner-Wadsworth-Emmons olefination. Re-... 

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