Polyacrylamide amines, reaction

Mannich Reaction. Aminomethylation of polyacrylamide with formaldehyde [50-00-0] and a secondary amine to produce a Mannich polyacrjiamide has been extensively studied (40). 

Hoffman Degradation. Polyacrylamide reacts with alkaline sodium hypochlorite [7681-52-9], NaOCl, or calcium hypochlorite [7778-54-3], Ca(OCl)2, to form a polymer with primary amine groups (58). Optimum conditions for the reaction include a slight molar excess of sodium hypochlorite, a large excess of sodium hydroxide, and low temperature (59). Cross-linking sometimes occurs if the polymer concentration is high. High temperatures can result in chain scission. 

Fig. 2. Functional groups on modified polyacrylamides (a) formed by reaction with dimethylamine and formaldehyde (Mannich reaction) (b), quatemized Mannich amine (c), carboxylate formed by acid or base-cataly2ed hydrolysis or copolymerization with sodium acrylate and (d), hydroxamate formed by...

The Mannich reaction of polyacrylamide with formaldehyde and an amine may be used for the obtaining product that contains N-methylol groups (or ethers or ethers thereoO-... 

The reaction rate increases when heated to temperatures up to 40°C. The amino derivatives can then be quaternized if desired. The N-methylol derivatives of polyacrylamide can be made cationic by heating with amines, or they can be made anionic by heating with aqueous bisulfite solution under basic conditions. 

Conversion of Graft Polyacrylamide to Amines via the Hofmann and Mannich Reactions... 

In a second step, the gel is fimctionahzed for NA attachment. Common methods for polyacrylamide gel fimctionahzation are based on the treatment of the polymerized support with reagents such as hydrazine or ethylenedi-amine. These treatments generate amine groups in the gel that can react with amine-modified ONDs via glutaraldehyde coupling, or directly with oxidized DNA probes (Fig. 15). Alternatively, the fimctional groups may be introduced by copolymerization reactions (e.g. co-polymerization with N-hydroxysuccinimide acryhc or oxirane acryhc derivatives) [59]. 

Amidines and sulfonamides have also been used as linkers for primary or secondary aliphatic amines (Entries 4, 5, and 7, Table 3.23). These derivatives are stable under basic and acidic reaction conditions and can only be cleaved by strong nucleophiles. Phenylalanine amides can be hydrolyzed by treatment with certain enzymes (Entry 8, Table 3.23), and can therefore be used for linking amines to supports compatible with enzyme-mediated reactions (CPG, some polyacrylamides, macroporous polystyrene, etc.). 

Molecules of type I are the classical product of reactions between monofunctional reactants. In many cases, they can be considered to be derived from the functionalization of a substrate or, reciprocally, of an amine, in order to attach chemical moieties purposely designed for specific uses, without substantially affecting the essential molecular structure. This is the case, for instance, of the antibiotic substance 494, which assumes hydrophilic properties upon aminomethylation of the pharmacologically active substrate having an amino acidic residue, or of the complexant agent 495,- as well as of the polyacrylamide Mannich base 502. - ... 

Finally, some important studies of the influence of pH in the reaction between formaldehyde and amine in biological. systems, in the aminomethylation of polyacrylamide, and in the use of aldehydes other than foiTnaldchyde- - lead to the conclusion that under acidic conditions, aldehyde attack by the amine is the rate-determining step. Under neutral or basic conditions the rate-determining step is hydroxyl elimination from the methylolamine HO—CH2—NR2 with formation of the methyl-cncimmonium cation. - Polarographic methods demonstrate that the maximum concentration of this last species occurs at a pH near 10. 

The yields of this reaction are typically 40—80%. 13C-nmr studies (41) indicate that the reaction is a second-order process between polyacrylamide and dimethylaminomethanol, which is one of the equilibrium products formed in the reaction between formaldehyde and dimethyl amine [124-40-3], C2H7N. The Mannich reaction is reversible. Extensive dialysis of Mannich polyacrylamides removes all of the dimethylaminomethyl substituents (42). 

Entrapment in polyacrylamide gel over a platinum grid matrix Glutaraldehyde-mediated reaction with a nylon-polyethyleneimine copolymer Reaction with macroporous aminated silo chrome coated with an acrolein-vinylpyridine copolymer Adsorption onto tannin coupled to amino hex y 1-cellulo se Entrapment in cellulose fibres Carbodi-imide-mediated reaction with chitosan... 

Sulfomethylation. The reaction of formaldehyde and sodium bisulfite [7631-90-5] with polyacrylamide under strongly alkaline conditions at low tem-peratnre to produce sulfomethylated polyacrylamides has been reported many times (123-125). A more recent publication (126) suggests, however, that the expected sulfomethyl substitution is not obtained under the previously described strongly alkaline conditions of pH 10-12. This nmr study indicates that hydrolysis of polyacrylamide occurs and the resulting ammonia reacts with the sodium bisulfite and formaldehyde to form sulfomethyl amines and hexamethylenetetramine... 

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