Reactions of the amino group

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. 

Amino acids undergo reactions characteristic of both their anine and carboxylic acid functional groups. Acylation is a typical reaction of the amino group. 

Nickel tetranitrophthalocyanine can be reduced to nickel tetraaminophthalocyanine with tin(II) chloride342 or sodium sulfide.319 343 To achieve better solubility, long alkanoyl side chains can be attached by the reaction of the amino groups with carboxylic acid chlorides.342 Copper(ll) tetranitrophthalocyanine 1 is reduced to the tetraamino compound 2 with sodium suinae." "... 

Substituted pyrimidine N-oxides such as 891 are converted analogously into their corresponding 4-substituted 2-cyano pyrimidines 892 and 4-substituted 6-cya-no pyrimidines 893 [18]. Likewise 2,4-substituted pyrimidine N-oxides 894 afford the 2,4-substituted 6-cyano pyrimidines 895 whereas the 2,6-dimethylpyrimidine-N-oxide 896 gives the 2,6-dimethyl-4-cyanopyrimidine 897 [18, 19] (Scheme 7.6). The 4,5-disubstituted pyridine N-oxides 898 are converted into 2-cyano-4,5-disubsti-tuted pyrimidines 899 and 4,5-disubstituted-6-cyano pyrimidines 900 [19] (Scheme 7.6). Whereas with most of the 4,5-substituents in 898 the 6-cyano pyrimidines 900 are formed nearly exclusively, combination of a 4-methoxy substituent with a 5-methoxy, 5-phenyl, 5-methyl, or 5-halo substituent gives rise to the exclusive formation of the 2-cyanopyrimidines 899 [19] (Scheme 7.6). The chemistry of pyrimidine N-oxides has been reviewed [20]. In the pyrazine series, 3-aminopyrazine N-ox-ide 901 affords, with TCS 14, NaCN, and triethylamine in DMF, 3-amino-2-cyano-pyrazine 902 in 80% yield and 5% amidine 903 [21, 22] which is apparently formed by reaction of the amino group in 902 with DMF in the presence of TCS 14 [23] (Scheme 7.7) (cf. also Section 4.2.2). Other 3-substituted pyrazine N-oxides react with 18 under a variety of conditions, e.g. in the presence of ZnBr2 [22]. 

The terminal amino and carboxyl groups react in the same way as the corresponding amino acids (acylation, animation, esterification, etc.). Some of the reactions of the amino groups (with ninhydrin, orthophthaldehyde, fluorescamine, etc.) are used for detection purposes, as will be discussed later. Peptides also react in ways that free amino acids do not, like the classic biuret reaction, which consists of the formation of a colored complex with a transition metal (Cu, Ni, etc.)... 

Acetylcholineesterase and choline oxidase Au foil was treated with cystamine to produce a base layer of ami-nothiolate units, was derivatized by reaction of the amino group and disodium-4,4 -diisothiocyanato-trans-stilbene-2,2 -disulfonate. Enzymes were immobilized at the isothiocyanate group via thiourea link. The bifunctional sensor for ACh was prepared by stepwise immobilization of four layers of the enzyme ChO and three layers of AChE. Choline generated was detected amperometircally with the use of 2,6-dichloro-phenolindophenol as a mediator in solution. Electrical communication between the enzyme and the electrode is achieved either by the use of ferrocenecar-boxylic acid as mediator in the assay buffer or by immobilization of [(ferrocenyl methyl)amino] hexa-noic acid on the enzyme layer. [92]... 

The most important reaction of amino acids from a biologic point of view is their ability to form peptide linkages, that is, the reaction of the amino group of one amino acid with the carboxyl group of another ... 

The browning reaction can be defined as the sequence of events that begins with the reaction of the amino group of amino acids, peptides, or proteins with a glycosidic hydroxyl group of sugars the sequence terminates with the formation of brown nitrogenous polymers or melanoidins (Ellis 1959). 

Unfortunately, introduction of the N-Dts group requires two steps, the first being reaction of the amino group with 0-ethyl S-carboxy methyl dithiocarbon-ate or 0,0-diethyl trithiodicarbonate [Scheme 8.20].32 The intermediate ethoxy-thiocarbonyl derivative is then treated with chlorocarbonylsulfenyl chloride, whereupon chloroethane is extruded to give the JV-Dts derivative. Since the first step is often accompanied by some noisome minor products, a solid-phase variant has been developed for the synthesis of N-Dts-protected amino acids.33... 

The carbamates represent the single most important family of protecting groups for all types of amines. All of the members of the carbamate family are easy to introduce by reaction of the amino group with chloroformates or various deri-... 

Various substituents can be present in the aromatic ring, but a free amino group lowers the yield significantly, even in the presence of additional hydrogen fluoride, probably due to side reactions of the amino group with sulfur tetrafluoride. ... 

The ionic bonding between the dye and the fiber is the result of the reaction of the amino groups on the fiber with acid groups on the dye. Generally the fastness of this dye depends on the rate with which the dye can diffuse through the fiber under the conditions of washing. Metal complex (cobalt or chromium) add dyes are used mainly on wool for improved fastness. 

The masking of the reactions of the amino groups of a-amino acids by forming the copper(II) complexes is found to be effective for a large number of other reagents, including fluorodinitrobenzene (59) and acetylation reagents (34f 56),... 

First, CD polyrotaxanes were synthesized by us by polymer analogous reaction of the amino groups of the PI-ll/a-CD pseudopolyrotaxane with nicotinoyl chloride. A 25% conversion of the imino groups led to a permanent 67% coverage of... 

The post-cross-linking reaction of the amino groups with the isocyanate groups of BICDPM decreases the number of protonable amino groups in the PVFA-co-PVAm chains. As expected, with increasing amount of cross-link-... 

The most representative general reactions of the amino group (see Figure 4.1) that are, more or less, easily reversible are acylation (+H3N—(CR R2—) C02 — R— CO—Nil—(CR R2—) C02H) and the analogoussulphonylation, thioacylation and thiocarbamylation. N-Benzylation can be reversed by catalytic hydrogenation. 

A more detailed survey of reactions of the amino group... 

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