Amino groups, determination

In most cases the presence of the amino group facilitates the introduction of further substituents into the same ring. Reaction media and conditions as well as type and position of the amino group determine the position of substitution. 

Amino acid polyamides —NH2 Amino group determination... 

Nowadays, both TVB-N and ammonia in muscle are generally determined conventionally by the Kjeldahl distillation method and the procedure reported by Antonacopoulos and Vyncke (1989), which is very time consuming, produces toxic vapors, and, moreover, gives yield values higher than expected as a result of the hydrolysis of the protein amino groups. Determination of TVB-N by FIA is therefore a major step forward in terms of time, money, and handling of toxic substances. 

Ultraviolet photoelectron spectroscopy allows the determination of ionization potentials. For thiazole the first experimental measurement using this technique was preformed by Salmona et al. (189) who later studied various alkyl and functional derivatives in the 2-position (190,191). Substitution of an hydrogen atom by an alkyl group destabilizes the first ionization potential, the perturbation being constant for tso-propyl and heavier substituents. Introduction in the 2-position of an amino group strongly destabilizes the first band and only slightly the second. 

Monomer Reactivity. The poly(amic acid) groups are formed by nucleophilic substitution by an amino group at a carbonyl carbon of an anhydride group. Therefore, the electrophilicity of the dianhydride is expected to be one of the most important parameters used to determine the reaction rate. There is a close relationship between the reaction rates and the electron affinities, of dianhydrides (12). These were independendy deterrnined by polarography. Stmctures and electron affinities of various dianhydrides are shown in Table 1. 

The amino group is readily dia2oti2ed in aqueous solution, and this reaction forms a basis for the assay of sulfas. Aldehydes also react to form anils, and the yellow product formed with 4-(dimethylamino)hen2a1dehyde can be used for detection in thiu-layer and paper chromatography. Chromatographic retention values have been deterrnined in a number of thiu layer systems, and have been used as an expression of the lipophilic character of sulfonamides (23). These values have corresponded well with Hansch lipophilic parameters determined in an isobutyl alcohol—water system. 

The ortho hydrogen atoms surrounding the central carbon atom show considerable steric overlap. Therefore, it can be assumed that the three aryl groups in the dye are not coplanar, but are twisted in such a fashion that the shape of the dye resembles that of a three-bladed propeller (9). Substitution in the para position of the three aryl groups determines the hue of the dye. When only one amino group is present, as in fuchsoriimine hydrochloride [84215-84-9] = 440 nm (2), the shade is a weak orange-yeUow. 

To determine the direction of primary attack at aminobutynones in the presence of competing hydroxyl and amino groups in the benzene ring, the reaction of 4-dimethylaminobut-3-yn-2-one with m-aminophenol has been examined (65-70°C, THF, 20 min). It was found that the hydroxyl group reacts first to form (9,A-ketenacetal of 4-dimethylamino-4-(m-aminophenoxy)-but-3-en-2-one (363) (88ZOR1165). 

The next step of our study was to determine which amino group of kasuganobiosamine binds with the residual moiety. 

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