Reactivity mechanism

A. D. Jenkins and A. Ledwith, eds.. Reactivity, Mechanism and Structure in Polymer Chemisty, Wiley-Interscience, New York, 1974. 

Bamford, C.H. In Reactivity, Mechanism, ami Structure in Polymer Chemistry Jenkins, A.D. Ledwith, A., Eds. Wiley-Interscience London, 1974 p 52. 

Wade Harper, J. Powers, J. C. Reaction of serine proteases with substituted 3-alkoxy-4-chloroisocoumarins and 3-alkoxy-7-amino-4-chloroisocoumarins new reactive mechanism-based inhibitors. Biochemistry 1985, 24, 7200-7213. 

Third, as the size and complexity of the biomolecular systems at hand further expand, there are more uncertainties in the molecular model itself. For example, the resolution of the X-ray structure may not be sufficiently high for identifying the locations of critical water molecules, ions and other components in the system the oxidation states and/or titration states of key reactive groups might be unclear. In those cases, it is important to couple QM/MM to other molecular simulation techniques to establish and to validate the microscopic models before elaborate calculations on the reactive mechanisms are investigated. In this context, pKa and various spectroscopic calculations [113,114] can be very relevant. 

The Diels-Alder reaction is among the most useful tools in organic chemistry. It has been the object of a great number of theoretical studies95-131 dealing with almost every one of the experimental aspects reactivity, mechanism, selectivity, solvent effects, catalysis and so on. 

Milling atmosphere, which is a neutral protective gas (helium or argon) during mechanical milling or hydrogen under pressure up to 0.9 MPa under reactive mechanical alloying processes. 

In a variant of the second method described earlier the premixed metallic powders (or pulverized ingots) are milled under hydrogen atmosphere to directly form an intermetallic hydride. It can be also viewed as hydrogen alloying of metal powders and powder mixtures in hydrogen alloying mills. This method is called a reactive mechanical alloying (RMA) or mechanochemical synthesis (MCS). 

Hydrogen Storage Characteristics ofMgH Synthesized by Reactive Mechanical (Ball) Milling of Mg... 

Much more efficient method of the synthesis of metal hydrides is a one-step method of reactive ball milling of elemental metal directly under hydrogen gas. The method of reactive mechanical alloying/milling of either elemental metals or preaUoyed... 

Table 2.15 Composition of powders and processing parameters for reactive mechanical milling of Mg-H powders [63]... 

For the sake of clarity, it must be mentioned that Huot et al. [24, 35] reported that at 350°C the absorption/desorption PCT plateau pressure hysteresis of the unmilled MgH was quite substantial, while the hysteresis of the same material milled for 20 h was very small. They argued that the plateau pressure difference observed for the uiimilled material was due to a very slow desorption kinetics which did not allow reaching equilibrium. In turn, ball milling increased desorption kinetics, which allowed reaching equilibrium and eliminated hysteresis. However, it must be noticed that the situation reported by Huot et al. is completely opposite to what is observed in Fig. 2.43, in which MgH synthesized by reactive mechanical milling shows a pressure hysteresis. 

Elansari et al. [201] developed a novel method of synthesizing alkali metal hydrides Na, KH, RbH, and CsH by reactive mechanical milling of pure alkaline metals under hydrogen pressure up to 30 bars in a planetary mill (Retsch PM 400). The reaction proceeds in 16 h and gives 3-15 g of very pure alkali metal hydride with FCC crystal structure (space group Fm3m). 

R.A. Varin, S. Li, A. Calka, Environmental degradation by hydrolysis of nanostructured P-MgHj hydride synthesized by controlled reactive mechanical milling, J. Alloys Compd. 376 (2004) 222-231. 

F.C. Gennari, F.J. Castro, G. Urretavizcaya, Hydrogen desorption behavior from magnesium hydrides synthesized by reactive mechanical aUoying, J. Alloys Compd. 321 (2001) 46-53. 

S. Orimo, H. Fujii, T. Yoshino, Reactive mechanical grinding of ZrNi under various partial pressures of hydrogen, J. Alloys Compd. 217 (1995) 287-294. 

S. Orimo, H. Fujii, Hydriding properties of the Mg Ni-H system synthesized by reactive mechanical grinding, /. Alloys Compd. 232 (1996) L16-L19. 

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