1,3-Ammonia elimination

Several alternatives are used to reduce ammonia elimination. Applied in relatively small quantities, urease inhibitors such as A-(n-butyl) thiophosphoric acid triamide reduce the rate of microbial hydrolysis of urea and increase its efficiency as a fertilizer (Manahan, 2005). Ammonia volatilization could also be reduced using a mixture of urea with tropical peat soil or free humic substances, such as humic and fulvic acids, isolated from peat soils (Bernard et al., 2009). Another application of green technologies is the use of thermal polyaspartate, a product formed by the condensation and base treatment of a natural compound, aspartic acid. This has been found to be effective in stimulating plant uptake of fertilizer thus reducing the amount of fertilizer required (Manahan, 2005). 

Both complexes 75 and 76 promote the hydrolysis of urea in a two-step process with the same initial rates (118). Heating of 75 or 76 in acetonitrile solution produced ammonia with kinetic first-order dependence on complex concentration and an observed rate constant of (7.7 0.5) x 10 " h to yield a cyanate complex as the reaction product. It remains unclear, however, which binding mode of urea (terminal or bridging as found in 76) facilitates the ehmination reaction. Ammonia elimination from the O bound terminal substrate appears to be in accordance with quantum chemical studies on that model system (34). Although no crystals could be obtained for the cyanate-containing reaction product, an analogous complex (77) with virtually identical Vas(OCN) (as = asymmetric) vibration (at 2164cm )... 

Bentley and Neuberger (20) provided early definitive evidence that glucose oxidase released D-glucono-8-lactone as the oxidation product of D-glucose. By analogy, therefore, it was considered likely that the first product (P) of the amino acid oxidases was the oc-imino acid which, through fairly rapid nonenzymatic hydration and ammonia elimination,... 

The previously reported 1,3-water loss from ionized 3-phenylpropanol (126) leads initially to 127. This is in contrast to the formation of ionized )5-methylstyrene (102) by 1,3-ammonia elimination from 3-phenylpropylamine (128). As 127 may also be generated by simple ring opening of cyclopropylbenzene (100)" it is not surprising that the CA mass spectra of CgH generated from either 126 or 100 are indistinguishable... 

Among the pyrolysis products of plasma-polymerized HMCTSN we found monomer (B), its oxy-derivative (A), octamethylcyclotetrasilazane (C) and bicyclic dimer (E) (Fig. 1 and Table I). It was difficult to identify the structure of compound D, but on the basis of mass spec-trometric data we speculate that it is an unstable product formed by ammonia elimination from the dimer molecule. 

Nucleoside O-phosphorothioates react with acrylonitrile at pH 8—9 to give 5-cyanoethyl derivatives, which may then be condensed with other nucleosides. Treatment with ammonia eliminates the cyanoethyl group, giving a dinucleoside 0,0-phosphorothioate. A number of these compounds, including Tp Tp T, have been prepared. ... 

A large group of pyridoxal-P-dependent enzymes catalyse reactions that affect as well as C of the amino acid and these can be divided into two main groups (Fig. 24) (a) those that involve the substitution of a group at ()8 replacement) and (b) those that involve the overall elimination of the a-hydrogen atom and the substituent with the formation of a-oxoacid and ammonia elimination-deamination). 

Acrylamide is polymerized free radically in acidified aqueous solution to produce poly(acrylamide) with the monomeric unit, I (see below). At temperatures above 140° C, structures 11 and 111 are formed by ammonia elimination and inter- or intramolecular imidation. When the medium is too strongly alkaline, the amide groups are saponiHed to carboxyl groups. In the polymerization of acrylamide with strong bases in organic solvents, however, poly()3-alanine) is produced with the monomeric unit, IV ... 

Figure 6.6 Comparison of liver-specific functions such as albumin secretion (a), ammonia elimination (b), and EROD activities (c) in AL and AL/GC sponges for monoculture and co-culture of hepatocytes with NIH3T3. (a) Albumin secretion rates for both systems were measured over 28 days in culture. ELISA specific for mouse albumin were used to quantify protein in 24h conditioned medium, (b) Ammonia elimination was compared between both systems on day 5 and 16 of culture, (c) EROD deethylase activity by cytochrome P4501A1 was compared between both systems on day 6 and 16 of culture. EROD activity was measured using the highly fluorescent resomfin in both systems. All data are represented as mean SDj jj (n = 6). Statistics (two-tailed paired Smdent s f-test) compared monoculture with co-culture P<0.05 and "P <0.01.

A work of Alexandrova et al. [671] addresses the decomposition of urea in neutral aqueous solution, which is most relevant as reference point for biological processes. Joint ab initio and QM/MM studies on alternative reaction pathways were carried out to identify preferred routes for the hydrolytic and ammonia-eliminative processes. The activation barrier for the direct ammonia elimination... 

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