Formaldehyde amino group reaction

Amino Resins. Amino resins (qv) include both urea- and melamine—formaldehyde condensation products. They are thermosets prepared similarly by the reaction of the amino groups in urea [57-13-6] or melamine [108-78-1] with formaldehyde to form the corresponding methylol derivatives, which are soluble in water or ethanol. To form plywood, particle board, and other wood products for adhesive or bonding purposes, a Hquid resin is mixed with some acid catalyst and sprayed on the boards or granules, then cured and cross-linked under heat and pressure. 

The amino group in cyanamide is very reactive toward formaldehyde. The reaction produces first an unstable hydroxymethyl derivative that... 

Formaldehyde, sulphur dioxide and glutaraldehyde react with amino groups. If these groups are essential for metabolic activity, cell death will follow reactions of this nature. Chlorinated fso-thiazolones as well as acting on -SH groups, (Section 3.4), can react with -NH2 groups. 

The synthesis of urea-formaldehyde resin takes place in two stages. In the first stage, urea is hydroxymethylolated by the addition of formaldehyde to the amino groups of urea (Figure 19.1). This reaction is in reality a series of reactions that lead to the formation of mono-, di-, and trimethy-lolureas. Tetramethylolurea does not appear to be produced, at least not in a detectable quantity. The addition of formaldehyde to urea takes place over the entire pH range, but the reaction rate is dependent on the pH. 

Fraenkel-Conrat H, Olcott HS. Reaction of formaldehyde with proteins. VI. Cross-linking of amino groups with phenol, imidazole, or indole groups. J. Biol. Chem. 1948 174 827-843. 

Figure 19.1 A schematic view of the common formaldehyde-induced modifications in proteins. Reactive methylol adducts are formed in the initial reaction between formaldehyde and cysteine or the amino groups of basic amino acid residues. The methylol adduct can subsequently undergo a dehydration reaction to form a Schiff s base. Adducted residues can undergo a second reaction to form methylene bridges or can convert to the ethoxymethyl adduct after the ethanol dehydration step.

The introduction of Calcobond dyes a few years later by American Cyanamid exploited a similar principle but incorporated the N-methylol groups into the dye molecule itself [132]. The labile chloro substituents in dichlorotriazine dyes were converted to amino groups by substitution with ammonia and the resulting melamine residue made cellulose-reactive again by reaction with formaldehyde (Scheme 7.59). A typical member of this range was Cl Reactive Red 92 (7.120). A characteristic problem of the Procion Resin process and of the... 

Condensation between the 4-amino group of the oxadiazole moiety of the triazolooxadiazolium inner salt 133 and formaldehyde furnished the methanediamino linked bis(inner salt) 92 from which the methanedinitroamine analogue 137 could be obtained on reaction with nitric acid (Scheme 20) <1995JHC1405>. 

The basic amino group of the 1-position in semicarbazide or thiosemi-carbazide may be used to react by a substitution reaction with activated halides [52], ethers [51], hydroxy [53], phenoxy [54], and amino groups [55] to yield substituted 1-semicarbazides or thiosemicarbazides. In addition, the amino group of the 1-position may add to electron-deficient double bonds [56]. Formaldehyde and other aldehydes may add to all the available free NH groups to give methylol, alkylol, or polymeric products under basic conditions [57]. Aldehydes or ketenes usually give semicarbazone derivatives, and these in turn are used analytically to identify the purity or structure of a known aldehyde [3]. 

Amino-3-chloro-5-trifluoromethylpyridine with electron-rich alkenes and formaldehyde in the presence of trifluoroacetic acid in boiling acetonitrile for 1 h yielded 6a,7,8,9,10,10a-hexahydro-6//-pyrido[l,2-a]-quinazolines (326) (96TL2615). The regiochemistry is dictated by the reaction of formaldehyde at the primary amino group. 

Gray et a I.146 radiolabeled a PNA using [14C]formaldehyde in a reductive formylation reaction to specifically methylate the exocyclic amino groups of the nucleotide bases. 

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