Ammonia fixation

FIGURE 8.29 Schematic showing ammonium fixation in clay lattice. 

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Thorn, K. A., and Mikita, M. A. (1992). Ammonia fixation by humic substances a nitrogen-15 and carbon-13 NMR study. Sci. Total Environ. 113, 67-87. 

Berger, M.G., Sprengart, M.L., Kusnan, M. and Fock, H.P. (1986) Ammonia fixation via glutamine synthetase and glutamate synthase in the crassulacean acid metabolism plant, Cissus quadrangularis. Plant Physiol., 81, 356-60. 

In another study, ammonia fixation of N-labeled ammonium hydroxide with Suwannee River fiilvic acid, IHHS peat and leonardite humic acid were examined by solution NMR with the application of INEPT and DEPT pulse sequences.(23) Similar reaction of ammonia with all three samples is reported. Most of the nitrogen incorporated seems to be in the form of indole and pyrrole followed by pyridine, pyrazine, amide and aminohydroquinone nitrogen. The authors also suggest a possible reaction mechanism to explain the formation of the heterocyclic compounds identified in the spectra. They also claimed that these results need to be substantiated through further work with model compounds and experiments with the reaction conditions, i.e., in which phenols will undergo oxidation to quinones when reacted with ammonia. 

Bennett (1949) observed that the nitrogen content of commmercial lignin was increased substantially by treatment with concentrated ammonium hydroxide, but methylation essentially prevented fixation of the nitrogen. His work seems to support the conclusions of Mattson and Koutler-Andersson that simultaneous oxidation and ammonia fixation take place by way of the phenolic hydroxyl groups. 

Mattson and Koutler-Andersson suggested that much or most of the nitrogen in soil humus originates from reaction with ammonia. They considered that in soils the oxidative ammonia fixation is related to the lignin fraction, and that aromatic rings and hydroxyl groups are involved. 

Fig.ll.1. Relation of ammonia fixation to pH in several soils. (From Broadbent et al., 1960.)... 

The findings of Burge and Broadbent (1961) that ammonia fixation in organic soils of varying carbon content is linearly correlated with their carbon contents, and that the reaction occurs both in the presence and absence of oxygen, is of considerable significance (Fig.l 1.2). In the presence of oxygen, 1 molecule of ammonia was fixed per 29 atoms... 

Fig, 11.2. Relationship between carbon content and ammonia fixation in several organic soils. (From Burge and Broadbent, 1961.)... 

Recently, Kobayashi and co-workers reported an interesting variant for the synthesis of homoallylic amines, dubbed an ammonia fixation reaction [128]. With this method, allylboronates are reacted with aldehydes in a solution of ethanolic ammonia. Despite the highly basic conditions, optically pure protected a-hydroxy aldehydes such as 89 can be employed without any observed racemization, and this approach was apphed to the synthesis of aminosugar derivatives via aminoalcohol product 90 (Equation 47). Unfortunately, the addition of a chiral camphor-based allylboronate to benzaldehyde led only to a low enantioselectivity (34% ee). Reactions with the ( )- and (2)-pinacol crotylboronates lead to the same diastereoselectivity seen in the corresponding reactions with aldehydes, affording the respective anti and syn products from a reaction mechanism that most likely involves the intermediacy of primary imines. 

The CAAC gold complex 43a catalysed the amination of terminal and internal alkynes (Scheme 5.8)." When using ammonia or a primary amine as substrate, imines were the major product. For ammonia fixation, the reaction was also successfully carried out using the preformed ammonia complex 43b as... 

MATTSON S. and KOUTLER-ANDERSSON E. 1942. The acid-base condition in vegetation, litter and humus V. Products of partial oxidation and ammonia fixation. Annals of the Royal Agricultural College, Sweden,... 

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