Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Biological N2 Reduction

In this article, the reasons for this mechanism in catalytic reduction of N2 will be considered, and results for electron transfer in biological N2 reduction and model synthetic systems will be compared. Hopefully, this consideration will lead to understanding how inert dinitrogen can be turned into a very active substrate readily reacting in solution in the presence of comparatively mild reducing agents. [Pg.1542]

Proteins containing iron-sulfur clusters are ubiquitous in nature, due primarily to their involvement in biological electron transfer reactions. In addition to functioning as simple reagents for electron transfer, protein-bound iron-sulfur clusters also function in catalysis of numerous redox reactions (e.g., H2 oxidation, N2 reduction) and, in some cases, of reactions that involve the addition or elimination of water to or from specific substrates (e.g., aconitase in the tricarboxylic acid cycle) (1). [Pg.258]

Not all biological oxidation-reduction reactions involve carbon. For example, in the conversion of molecular nitrogen to ammonia, 6H1 + 6e + N2 2NH3, the nitrogen atoms are reduced. [Pg.508]

Biological N2 fixation (1), i.e., the reduction of N2 to NH3 catalyzed by FeMo, FeV, or FeFe nitrogenases, is one of the fundamental synthetic processes of nature (2-4). In spite of intense efforts over the last decades, its molecular mechanism is poorly understood, in particular because the pivotal chemical question has remained unanswered how do nitrogenases achieve to activate and convert the inert N2 molecule to ammonia under ambient conditions and mild redox potentials. [Pg.56]

All mechanistic proposals for biological N2 fixation are left with the problem to explain how nitrogenases enable the catalytic N2 reduction at mild biological reduction potentials (6,8). These reduction potentials probably represent the biggest challenge in the search for synthetic competitive catalysts that exhibit nitrogenase-like activity. [Pg.56]

Figure 10.5 Major processes involved in the biogeochemical cycling of N in estuaries and the coastal ocean (1) biological N2 fixation (2) ammonia assimilation (3) nitrification (4) assimilatory NC>3 reduction (5) ammonification or N remineralization (6) ammonium oxidation (speculative at this time) (7) denitrification and dissimilatory NO3 reduction to NH4+ and (8) assimilation of dissolved organic nitrogen (DON). (Modified from Libes, 1992.)... Figure 10.5 Major processes involved in the biogeochemical cycling of N in estuaries and the coastal ocean (1) biological N2 fixation (2) ammonia assimilation (3) nitrification (4) assimilatory NC>3 reduction (5) ammonification or N remineralization (6) ammonium oxidation (speculative at this time) (7) denitrification and dissimilatory NO3 reduction to NH4+ and (8) assimilation of dissolved organic nitrogen (DON). (Modified from Libes, 1992.)...
Biological N2 fixation is catalyzed by Fe/Mo, Fe/V, or FeFe (the Fe-only) nitrogenases (150, 151). The extremely different reaction conditions of the biological and the Haber-Bosch processes of N2 reduction, that is, standard temperature and pressure and biological redox potentials on the one hand, red-hot temperatures and high pressures on the other hand, make the quest for low molecular weight competitive catalysts particularly challenging. [Pg.661]

The yields were found also to increase in the presence of phosphines, particularly trimethyl or tributyl phosphine. After all the improvements of the catalyst and reaction conditions the system became by far the most active of known non-biological catalytic systems for the reduction of dinitrogen at ambient temperature and pressure. The specific activity (the rate of N2 reduction per mole of the complex) reached and even exceeded that of nitrogenase. Up to 1000 turnovers relative to the molybdenum complex can be observed at atmospheric pressure and more than 10 000 turnovers at elevated N2 pressures. [Pg.1563]

Nitrogen fixation is the processes by which N2 is converted to any nitrogen compound where nitrogen has a nonzero oxidation state. Historically, the most common process has been the biologically driven reduction of N2 to NH3 or NH4. However, currently anthropogenic ally enhanced nitrogen fixation dominates on continents (see Section 8.12.4). [Pg.4424]

In molecular chemistry (including biology), the reduction of metal-bonded N2 and metal-bonded nitrido complexes involves protonation-single electron transfer sequences. [Pg.463]


See other pages where Biological N2 Reduction is mentioned: [Pg.362]    [Pg.363]    [Pg.263]    [Pg.83]    [Pg.83]    [Pg.362]    [Pg.363]    [Pg.263]    [Pg.83]    [Pg.83]    [Pg.82]    [Pg.1036]    [Pg.381]    [Pg.287]    [Pg.310]    [Pg.311]    [Pg.344]    [Pg.515]    [Pg.369]    [Pg.668]    [Pg.668]    [Pg.240]    [Pg.242]    [Pg.3101]    [Pg.1541]    [Pg.1541]    [Pg.1549]    [Pg.2601]    [Pg.147]    [Pg.240]    [Pg.242]    [Pg.413]    [Pg.3100]    [Pg.243]    [Pg.328]    [Pg.575]    [Pg.965]    [Pg.455]    [Pg.303]    [Pg.450]    [Pg.203]    [Pg.90]    [Pg.96]   


SEARCH



Biological reductants

Reduction, biological

© 2024 chempedia.info