Formaldehyde results

Replacing acetaldehyde with acetone and using a co-feed of formaldehyde and ammonia give mainly 2,6-lutidine (5). However, leaving out the formaldehyde results in production of 2,4,6-coUidine (8) as the primary product. 

Respiratory sensitizers, e.g. isoeyanates or formaldehyde, result, in mild eases, in a sense of tightness of the ehest and oeeasionally a troublesome eough. Severe eases involve bronehial asdima. Refer to Table 5.6. With sueh sensitizers, eomplete eessation of eontaet is often followed by rapid reeovery but no further exposure is generally permitted. 

Phenolic oligomers are prepared by reacting phenol or substituted phenols with formaldehyde or other aldehydes. Depending on the reaction conditions (e.g., pH) and the ratio of phenol to formaldehyde, two types of phenolic resins are obtained. Novolacs are derived from an excess of phenol under neutral to acidic conditions, while reactions under basic conditions using an excess of formaldehyde result in resoles. 

Figure 16.3 Conceptual illustration of two peptides before (left) and after (right) a chemical reaction with formaldehyde. The amino acids are represented as circles. In this particular peptide, a tyrosine (Y) is located within the epitope (shaded circles). An arginine (R) is located elsewhere in the peptide. Formaldehyde results in the formation of a covalent bond between the two residues, due to a Mannich condensation reaction, as shown on the right. The new configuration prevents antibodies from binding to the epitope on the left. 

It has been found that the treatment of gramicidin with formaldehyde results in the formation of a compound with the same antibiotic activity but with much less hemolytic activity110,1H,112,113,119 ... 

Properties of composites obtained by template poly condensation of urea and formaldehyde in the presence of poly(acrylic acid) were described by Papisov et al. Products of template polycondensation obtained for 1 1 ratio of template to monomers are typical glasses, but elastic deformation up to 50% at 90°C is quite remarkable. This behavior is quite different from composites polyacrylic acid-urea-formaldehyde polymer obtained by conventional methods. Introduction of polyacrylic acid to the reacting system of urea-formaldehyde, even in a very small quantity (2-5%) leads to fibrilization of the product structure. Materials obtained have a high compressive strength (30-100 kg/cm ). Further polycondensation of the excess of urea and formaldehyde results in fibrillar structure composites. Structure and properties of such composites can be widely varied by changes in initial composition and reaction conditions. 

Pinene is similar to a-pinene in its reactions. Pyrolytic cleavage to myrcene, the starting material for acyclic terpenes, is used on an industrial scale. Addition of formaldehyde results in the formation of nopol nopyl acetate is used as a fragrance material. /3-Pinene is produced in large quantities by distillation of turpentine oils. It is used as a fragrance material in household perfumery. However, most /3-pinene is used in the production of myrcene. 

The large excess of formaldehyde resulted in the hydroxymethylation of 13 in yields of about 50% hydroxymethylation. This yield was obtained within 15 minutes and remained constant for over 6 hours. The number of unsubstituted aromatic positions decreased from 0.6/model compound after 15 minutes to 0.2 after 1 hour reaction time. However, after only 15 minutes about one methylene linkage per model compound occurred, indicating substantial methylene linkage formation. 

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). 

Bisphenol F epoxy resins are produced by condensing phenol with formaldehyde, resulting in a mixture of isomers and higher-MW condensation products. Bisphenol F epoxy resins have lower viscosity then DGEB A epoxy resins for the same molecular weight (or number of repeating units n). Cured bisphenol F epoxy resins also have increased solvent resistance. 

Reaction (18) was suggested by Bates and Spence in 193111 to occur in the photooxidation of methyl iodide. Formaldehyde was first detected by Hoare68 as a product of the photooxidation of acetone. He showed that addition of formaldehyde resulted in the production of more carbon monoxide and Caldwell and Hoare81 have now shown that the formaldehyde concentration tends to reach a maximum as an experiment is continued for longer periods. It appears that abstraction of a hydrogen atom from formaldehyde may be several hundred times easier than from acetone,67 so only results of experiments with conversions considerably less than 1% may be valid for formaldehyde yields. 

Ozonolysis data are used to determine the location of the double bonds. The acetone fragment, which comes from carbon atoms 1 and 2 of 2,6-dimethyloctane, fixes the position of one double bond. Formaldehyde results from ozonolysis of a double bond at the other end of B-ocimene. Placement of the other fragments to conform to the carbon skeleton yields the following structural formula for B-ocimene. 

Table 2.31 Optimized geometries (A and degs) and energetics (kcal/mol) of H-bond between water and formaldehyde . Results at SCF level, not corrected for BSSE. See Fig. 2.12 for atom numbering scheme.

Mcthoxycarbenium ion is an ambident electrophile reaction can occur at either C or O. Nucleophilic attack at the C atom results in mcthoxymetbylation. Displacement of formaldehyde results in mcthylation of the nucleophile. The latter reaction is prevalent with aromatics. Thus the reaction of the reagent with benzene gives toluene in high yield. 

Phenylpyrimidoazepine 612 readily undergoes 1,4-dipolar cycloaddition reactions (85Ag604, 85CB4567). The reaction of compound 612 and formaldehyde resulted in the formation of tricyclic compound 613 in a regiospecific... 

The synthesis of the indoloquinolizadine alkaloid deplancheine (52 Scheme 24), using an exocyclic variant of an iminium ion initiated vinylsilane cyclization, has been reported by Malone and Ovemuui. Thus, treatment of vinylsilane (51) with formaldehyde resulted in the generation of an intermediate im-... 

Aldehydes can be prepared by the dehydrogenation of a primary alcohol. Formaldehyde results from the dehydrogenation of methanol at high temperatures with an iron oxide-molybdenum oxide catalyst ... 

Treatment of the base [lxxx] with formaldehyde resulted in production of N-methyhsomorphinane, apparently a C-14 epimer of Grewe s N-methylmorphinane and identical with one of the by-products of the preparation of the latter [30], Hofmann degradation of N-methyliso-morphinane methiodide leads to a methine base, zinc-dust distillation of which affords l 2 3 4-tetrahydrophenanthrene, The methine can be reduced to a dihydromethine [30]. 

Intermediate-duration exposure of animals to orally administered formaldehyde resulted in a more consistent picture of mortality. Vargova et al. (1993) observed no treatment-related mortality in male Wistar rats exposed to doses of formaldehyde by gavage of 80 mg/kg/day for 4 weeks. No deaths were reported in weanling SPF-bred rats (Cpb WU, Wistar random) that received up to 125 mg/kg/day formaldehyde in their drinking water for 4 weeks (Til et al. 1988b), in male and female Sprague-Dawley... 

Gerin M, Siemiatcki J, Nadon L, et al. 1989. Cancer risks due to occupational exposure to formaldehyde Results of a multi-site case-control study in Montreal, Canada. Int J Cancer 44 53-58. 

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