Formaldehyde, reaction

Hippel, P.H. von, Wang, K.-Y. Dynamic aspects of native DNA structure kinetics of the formaldehyde reaction with calf thymus DNA. J. Mol. Biol. 61 (1971) 587-613... 

Strong-Acid Catalysts, Novolak Resins. PhenoHc novolaks are thermoplastic resins having a molecular weight of 500—5000 and a glass-transition temperature, T, of 45—70°C. The phenol—formaldehyde reactions are carried to their energetic completion, allowing isolation of the resin ... 

Quinone dioximes, alkylphenol disulfides, and phenol—formaldehyde reaction products are used to cross-link halobutyl mbbers. In some cases, nonhalogenated butyl mbber can be cross-linked by these materials if there is some other source of halogen in the formulation. Alkylphenol disulfides are used in halobutyl innerliners for tires. Methylol phenol—formaldehyde resins are used for heat resistance in tire curing bladders. Bisphenols, accelerated by phosphonium salts, are used to cross-link fluorocarbon mbbers. 

Urea—Formaldehyde Reaction Products. Urea—formaldehyde (UF) reaction products represent one of the older controlled release nitrogen technologies. An early disclosure of the reaction products of urea [57-13-6] and formaldehyde [50-00-0] was made in 1936 (1) (Amino resins and plastics). In 1948, the USDA reported that urea (qv) and formaldehyde (qv) could react to produce a controlled release fertilizer at urea to formaldehyde mole ratios (UF ratio) greater than one (2). 

Urea—formaldehyde reaction products represented the first synthetically produced form of controlled release nitrogen and were commercialized in 1955 under the trade names Uramite (DuPont) and Nitroform (Nitroform Corp.). 

The urea—formaldehyde reaction results in a distribution of methylene urea (MU) polymers of varying molecular weights or polymer chain lengths and of varying water solubiUty. 

Liquid Compositions. Urea—formaldehyde reaction products also are available commercially as Hquids that can be categorized into two classes, ie, water suspensions and water solutions. 

The nitrogen content of granular urea—formaldehyde reaction products typicahy ranges from 35 to 42% depending on the methylene urea polymer distribution. 

Once in the soil solution, urea—formaldehyde reaction products are converted to plant available nitrogen through either microbial decomposition or hydrolysis. Microbial decomposition is the primary mechanism. The carbon in the methylene urea polymers is the site of microbial activity. Environmental factors that affect soil microbial activity also affect the nitrogen availabiUty of UF products. These factors include soil temperature, moisture, pH, and aeration or oxygen availabiUty. 

The initial phenol-formaldehyde reaction products may be of two types, novolaks and resols. 

These results predict that the hydroxycarbene to formaldehyde reaction will proceed significantly more easily than the fonvard reaction. However, for this problem, electron correlation is needed for good quantitative values. For example, the MP4/6-31G(d,p) level predicts a value of 86.6 kcal mol" for the activation energy of the forward reaction. 

Fluorenylamine, 40,5 Formaldehyde, reaction with diethyl malonate to form diethyl bis-(hydroxymethyl)malonate, 40,27 Formamide, condensation with 4,4-dimethoxy-2-butanone to give 4-methylpyrimidine, 43, 77 Formic acid, and hydrogen peroxide, with indcne, 41, 53... 

Phenol-formaldehyde reactions catalyzed by zinc acetate as opposed to strong acids have been investigated, but this results in lower yields and requires longer reaction times. The reported ortho-ortho content yield was as high as 97%. Several divalent metal species such as Ca, Ba, Sr, Mg, Zn, Co, and Pb combined with an organic acid (such as sulfonic and/or fluoroboric acid) improved the reaction efficiencies.14 The importance of an acid catalyst was attributed to facilitated decomposition of any dibenzyl ether groups formed in the process. It was also found that reaction rates could be accelerated with continuous azeotropic removal of water. 

Figure 7.22 Reaction pathways for phenol-formaldehyde reactions under alkaline conditions.

Base-catalyzed phenol-formaldehyde reactions exhibit second-order kinetics [Eq. (5)]. Several alkylphenols such as cresols also follow this rate equation ... 

TABLE 7.5 Relative Positional Reaction Rates in Base-Catalyzed Phenol-Formaldehyde Reaction... 

The reaction conditions, formaldehyde-to-phenol ratios, and concentration and type of catalyst govern the mechanisms and kinetics of resole syntheses. Higher formaldehyde-to-phenol ratios accelerate the reaction rates. This is to be expected since phenol-formaldehyde reactions follow second-order kinetics. Increased hydroxymethyl substitution on phenols due to higher formaldehyde compositions also leads to more condensation products.55... 

Figure 7.30 Mechanism of phenol and formaldehyde reaction using base catalyst involving the formation of chelate.

Phenol-formaldehyde reactions, 399, 380 base-catalyzed, 400-402 Phenol-formaldehyde resins, modified, 410-411... 

The detection limits for triazines are 300 ng [7] and for urea formaldehyde reaction products they are 1 to 5 pg substance per chromatogram zone [1]. 

In this paper, the preparation, characterization and the catalytic performance of the Moo.esVoasWo.ioOx-mixed oxide as a partial oxidation catalyst for the methanol to formaldehyde reaction was studied. 

Although the condensation of phenol with formaldehyde has been known for more than 100 years, it is only recently that the reaction could be studied in detail. Recent developments in analytical instrumentation like GC, GPC, HPLC, IR spectroscopy and NMR spectroscopy have made it possible for the intermediates involved in such reactions to be characterized and determined (1.-6). In addition, high speed computers can now be used to simulate the complicated multi-component, multi-path kinetic schemes involved in phenol-formaldehyde reactions (6-27) and optimization routines can be used in conjunction with computer-based models for phenol-formaldehyde reactions to estimate, from experimental data, reaction rates for the various processes involved. The combined use of precise analytical data and of computer-based techniques to analyze such data has been very fruitful. 

A reasonable objection to any in vitro model is whether it accurately mirrors the actual process. A strength of this model is that the peptides in the array, mounted on the microscope glass slide, are the very same as the antibody epitopes in the native proteins. Therefore, the types of formaldehyde-induced chemical reactions at or near the epitope are the same as would likely occur in a tissue sample. An additional strength of the model is that the experimental data using the peptide array completely account for the loss of immunoreactivity after formalin fixation and the recovery of immunoreactivity after antigen retrieval (Fig. 16.5). Nonetheless, our data do not prove that the model accurately represents formaldehyde reactions in tissue specimens. For example, our data do not exclude other causes of steric interference. 

Assuming that the Final Protein -Formaldehyde Reactions Found After Paraff n-Embedding Are Different from Those Found After Aqueous Fixation, Will Careful Heating in Nonpolar Solvents Assist in the Reversal of These Reactions ... 

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