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Formaldehyde, derivative

Isocyanates. The commodity isocyanates TDI and PMDI ate most widely used in the manufacture of urethane polymers (see also Isocyanates, organic). The former is an 80 20 mixture of 2,4- and 2,6-isomers, respectively the latter a polymeric isocyanate obtained by phosgenation of aniline—formaldehyde-derived polyamines. A coproduct in the manufacture of PMDI is 4,4 -methylenebis(phenyHsocyanate) (MDI). A 65 35 mixture of 2,4- and 2,6-TDI, pure 2,4-TDI and MDI enriched in the 2,4 -isomer are also available. The manufacture of TDI involves the dinitration of toluene, catalytic hydrogenation to the diamines, and phosgenation. Separation of the undesired 2,3-isomer is necessary because its presence interferes with polymerization (13). [Pg.344]

Other amino resins besides MF resins are used to a lesser degree in coatings. Urea—formaldehyde resins are used in some coatings for wood furniture because these resins cross-link at lower temperatures than MF resins and the higher water resistance and exterior durabiUty that can be obtained using MF resins are not needed. Ethers of formaldehyde derivatives of 6-phenyl-l,3,5-triazine-2,4-diamine [91-76-9] (benzoguanamine resins) give... [Pg.338]

H2/Pd-C. If hydrogenation is carried out in the presence of (B0C)20, the released amine is directly converted to the BOC derivative. The formation of A-methylated lysines during the hydrogenolysis of a Z group has been observed with MeOH/DMF as the solvent. Formaldehyde derived oxidatively from methanol is the source of the methyl carbon. ... [Pg.532]

Resole syntheses entail substitution of formaldehyde (or formaldehyde derivatives) on phenolic ortho and para positions followed by methylol condensation reactions which form dimers and oligomers. Under basic conditions, pheno-late rings are the reactive species for electrophilic aromatic substitution reactions. A simplified mechanism is generally used to depict the formaldehyde substitution on the phenol rings (Fig. 7.21). It should be noted that this mechanism does not account for pH effects, the type of catalyst, or the formation of hemiformals. Mixtures of mono-, di-, and trihydroxymethyl-substituted phenols are produced. [Pg.398]

Sulfur cross-links have limited stability at elevated temperatures and can rearrange to form new cross-links. These results in poor permanent set and creep for vulcanizates when exposed for long periods of time at high temperatures. Resin cure systems provide C-C cross-links and heat stability. Alkyl phenol-formaldehyde derivatives are usually employed for tire bladder application. Typical vulcanization system is shown in Table 14.24. The properties are summarized in Tables 14.25 and 14.26. [Pg.433]

There is not much to be said about the use of micro reactors for bulk chemicals and commodities. Worz et al. are so far the only ones who have disclosed their work on the potential of micro-structured reactors for the optimization of chemical processes performed on a large scale ofindustrial relevance [110,112,154,288-290]. This included a fast exothermic liquid/liquid two-phase reaction, which was used for the industrial production of a vitamin intermediate product, and a selective oxidation reaction for an intermediate, a substituted formaldehyde derivative. [Pg.100]

The following procedure adapted from Prato et al. (1996) is an example of how glycine and formaldehyde derivatives may be used to create fullerene modifications for subsequent bioconjugation purposes. [Pg.629]

Similar to the fullerene modifications using either glycine/formaldehyde derivatives or oxazolidinone compounds, Maggini and Scorrano (1993) found that aziridines could yield similar pyrrolidine derivatives. Heating aziridine compounds in toluene was found to result in ring... [Pg.632]

Since the initial studies, the substrate scope has expanded to include heteroatom-substituted ketones [208-216], cyclic ketones [217] and aldehydes [211, 218-226] as donors, and formaldehyde-derived imines [218, 227-232] as well as glyoxylate-derived imines [96, 220, 233-237] as acceptors. In addition, several alternative catalysts to proline have been pursued [238-242]. [Pg.51]

Although the parent formaldehyde-derived dioxirane (H2CO2) was the first of this intriguing class of cyclic peroxides to be prepared and spectrally characterized in 1976, the conversion of aldehydes into the corresponding dioxiranes by treatment with Caroate was deemed difficult because of the expectedly facile Baeyer-Villiger oxidation of the aldehydes to their carboxylic acids. Most gratifyingly, however, is that it was recently demonstrated that optically active aldehydes may also serve as promising catalysts for asymmetric epoxidations. For example, ee values up to 94% were obtained with the aldehyde 14 as dioxirane precursor. [Pg.1150]

A number of expls have been prepd from raw materials involving formaldehyde. Although most of the formaldehyde expls are prepd from formaldehyde derivatives, several expls can be prepd directly in one operation from formaldehyde or anhydrous formaldehyde, or its polymer, paraformaldehyde. Walker (Ref 38), in his book on formaldehyde, gives a brief description of expls derived from it. For convenience, we divide them into two groups — those obtained directly from formaldehyde and those from formaldehyde derivatives... [Pg.547]

The first 2,5-dialkyl (Me) substituted phosphole was synthesized by addition of PhPH2 [or its formaldehyde derivative PhP(CH20H)2] to 2,4-hexadiyne (equation (57)) (67AG(E)87>. [Pg.520]

The range of JCH expands considerably if more than one electron-withdrawing substituent is found at the coupling carbon. This trend is exemplified in a series of formaldehyde derivatives (Table 3.6) and in di- and trisubstituted methanes, CH2X2 and CHX, (Table 3.5). Whereas methyl iodide, bromide, chloride, and fluoride show almost equal JCH values of about 150 Hz, the coupling constants increase almost linearly for each additional substituent at the methyl carbon, but individually for each kind of substituent. [Pg.135]

RESINS (Acetal). These are thermoplastic resins, obtainable both as homopolymers and copolymers, and produced principally from formaldehyde or formaldehyde derivative. Acetal resins have the highest fatigue endurance of commercial thermoplastics. A variety of ionic initiators, such as tertiary amines and quaternary ammonium salts, are used to effect polymerization of formaldehyde. Chain transfer, shown by the following reactions, controls the molecular weight of resulting resins ... [Pg.1436]

Wines may contain formaldehyde derived from urotropine (hexamethylenetetramine) used to desulphite them. In this case 50 c.c. of the wine are acidified with 10 drops of sulphuric add and distilled slowly. The first 10 c.c. of distillate are discarded and the next 20 c.c. divided into two portions and tested for formaldehyde. [Pg.215]

In nonpolar solvents such as CH2C12 the bridging carbonyl (X) is formed preferentially. It has a remarkably low carbonyl stretching frequency of 1638 cm-1 and an X-ray structure determination of the corresponding bis(diphenylarsino)methane complex shows that there is no Pt-Pt bond (3,9,10). The complex therefore is considered as a dimetal-lated formaldehyde derivative. [Pg.235]

While the selective interactions of functionalised calixarenes with cations have been studied broadly for almost three decades, the application of cal-ixarene-based receptors for anion recognition is a relatively new research topic [2]. This review is focused on recent developments in the design and synthesis of calixarene-based anion receptors. Although the name calixarene was originally designated only for phenol-formaldehyde derivatives 1, recently many structural variations and mutations have been formed. Some of them, such as calixpyrroles [3], are widely used for anion recognition nevertheless, this review is restricted only to classical calixarenes 1 and newly discovered thiacalix-arenes 2 [4]. [Pg.66]

The thiazole formed under the conditions used by Cemy and Davidek250 was only singly labelled, the label appearing at C-2, suggesting that the compound had been formed from cysteamine and formaldehyde derived from ribose (cf. ref. 258). [Pg.79]

In another experiment, 13C-labeled (98%) formaldehyde was used, but in a much smaller quantity (0.4 mole/C9 unit) than with the unlabeled (1% natural abundance) 13C-material. The result was an enormous increase in intensity of the formaldehyde, derived resonances (Figure 4c), particularly those centered around 35 ppm that were barely detectable before (Figure 4b). A broad envelope of overlapping resonances in this region was also observed with the alkaline treatment of VII in the presence of H213C=0 (12). The observation that considerable resonances are still present in the 121-124 ppm region indicates that, with the smaller amount of formaldehyde, there are still many unsubstituted C-5 positions. [Pg.34]

Cause of denaturation. Many hypotheses have been proposed to explain the denaturation of muscle proteins (9-17). These hypotheses include 1) the effects of inorganic salts concentrated into the liquid phase of the frozen system 2) water-activity relations 3) reactions with lipids 4) reaction with formaldehyde derived from trimethyl amine (in fish) 5) auto-oxidation ... [Pg.111]

Preparation of calibration curve for formaldehyde analysis. The calibration curve for thiazolidine (formaldehyde derivative) was prepared with N-methylacetamide as an internal standard. [Pg.68]

Preformed iminium salts have been used extensively in organic synthesis. The facility of the condensation is a function of iminium salt substitution. Treatment of formaldehyde-derived methyl(methylene)ammonium halides (or trifluoroacetates) (46) with Grignard and lithium reagents results in the high yield formation of dimethylaminomethyl-containing compounds (47). Subsequent oxidation or alkylation of these products has been employed to generate terminal alkenes (48 Scheme 7). As expected, addition yields are modest for the mote-hindered iminium salts derived frrom other aldehydes and are somewhat lower for those derived from cyclic ketones. ... [Pg.366]

Summary Mono(silyl)hydrazines condense to bis(silyl)hydrazines at higher temperature. The degree of oligomerization of mono- and dilithiated silylhydrazines in the crystal depends on the bulkiness of the substituents. Reactions of lithiated silylhydrazines with fluorosilanes lead, for example, to the formation of tetrakis(silyl)-hydrazines, six-, four- and five-membered rings. Formaldehyde derivatives of mono-(silyl)hydrazones are obtained in a reaction of mono(silyl)hydrazines with aqueous formaldehyde solution. 0-Silylpyrazolones can be synthesized by treating mono(silyl)-hydrazines with acetoacetic ester. A dipyrazolonesilane is formed in the reaction of an O-silylpyrazolone with dichlorodimethylsilane. [Pg.358]

The first stable monomeric formaldehyde derivatives are formed by reaction of mono(silyl)hydrazines with aqueous formaldehyde solution. [Pg.361]

Donaruma and coworkers have studied copolymers of various sulfa drugs with formaldehyde or dimethylolurea. These copolymers often exhibited bacteriostatic activity and in some cases this activity level was higher than with the corresponding, monomeric, sulfa drug. The polymers often showed lower toxicity levels and, in general, the dimethylolurea derivatives showed higher bacteriostatic activity than did the formaldehyde derivatives. In earlier work, Donaruma and coworkers also prepared some antimalarlal, polymeric sulfomes and some bloactlve tropone derivatives (1,13). [Pg.5]


See other pages where Formaldehyde, derivative is mentioned: [Pg.498]    [Pg.42]    [Pg.338]    [Pg.371]    [Pg.442]    [Pg.89]    [Pg.729]    [Pg.1150]    [Pg.229]    [Pg.639]    [Pg.361]    [Pg.408]    [Pg.384]    [Pg.305]    [Pg.101]    [Pg.140]    [Pg.207]    [Pg.623]    [Pg.827]    [Pg.1]   
See also in sourсe #XX -- [ Pg.232 ]




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