Amines active hydrogen determination

Amines are the most frequent curing agents, and the curing mechanism is determined by a simple addition reaction of active hydrogens of polyamines to epoxy groups. Consequently, the structures of the cured resins are not much different from the ideal structure shown in Fig. 1 a. Some examples of polyamines are shown in Table 2. The structures of the cured resins obtained from DGEBA and stoichiometrically equivalent amounts of polyamines are shown in Fig. 1 a, and differ in the 0 segment. 

Use Analytical reagent for active hydrogen atoms in organic compounds also to determine water, alcohols, and amines in inert solvents. 

Zenkevich, I.G. Determination of the number of functional groups with active hydrogen atoms in phenols and aromatic amines by HPLC. Zh. Phys. Khim. (Russ.) 1998, 72 (6), 1131-1136. 

The N—H partial structure confers upon primary and secondary amines a set of properties which can be connected mainly with two phenomena active hydrogen and hydrogen bonding. Both are interrelated, although the methods of determining the former are usually chemicar, while the latter is investigated mainly through physical properties as shown in section lI.E. 

Various methods have been used for detecting and determining active hydrogen in general, and they can be applied with diverse degrees of success to amines. 

Divalent copper, cobalt, nickel, and vanadyl ions promote chemiluminescence from the luminol—hydrogen peroxide reaction, which can be used to determine these metals to concentrations of 1—10 ppb (272,273). The light intensity is generally linear with metal concentration of 10 to 10 M range (272). Manganese(II) can also be determined when an amine is added to increase its reduction potential by stabili2ing Mn (ITT) (272). Since all of these ions are active, ion exchange must be used for deterrnination of a particular metal in mixtures (274). 

Fe/MgO catalysts with 5 to 30 mol % Fe have been prepared by impregnation and coprecipitation. Their reducibility has been measured and a comparison made of their Fe° surface areas. Catalysts prepared via coprecipitation yielded larger iron areas than those via impregnation. The activity and selectivity of the reduced catalysts for the hydrogenation of propanenitrile at 20-30 bar and 473 K and of ethanenitrile at 1 bar and 508 K have been determined. The most active catalysts are those prepared by coprecipitation and they show high selectivity for primary amines. The activity for ethanenitrile hydrogenation correlates with the iron surface area. 

Supported iron catalysts are notoriously difficult to reduce [6-8] and thus a substantial fraction of the iron can be expected to remain inactive for the catalysis of hydrogenation. Particular attention has therefore been paid to the preparation of Fe/MgO catalysts by several different methods and examination of their effectiveness in producing metallic iron of adequate specific surface area after reduction in hydrogen. The activity and selectivity for primary amine formation have been determined for the hydrogenation of ethanenitrile (acetonitrile) and propanenitrile. 

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