Reactions mechanochemical

Hall AK, JM Harrowfied, RJ Hart, PG McCormick (1996) Mechanochemical reaction of DDT with calcium oxide. Environ Sci Technol 30 3401-3407. 

M. Carey-Lea, (1892) Quicksilver from cinnabar The first documented mechanochemical reaction, J. Metals 34 46 Phil. Mag. cited after Takac Laszlo, Jan 2000, pp. 12-13. 

In another recent development Kojima et al. [103] mechanically milled LiH and Al without and with the TiClj additive for 24 h in a H gas atmosphere at a pressure of 1 MPa at room temperature. They found that a sm l amount of LiAlH could be directly synthesized by the mechanochemical reaction with concomitant formation of LijAlHg. The latter can be relatively easily formed by mechanochemical synthesis of LiAlH and LiH as originally reported by Zaluski et al. [71] and later by Balema et al. [104],... 

Y. Kojima, Y. Kawai, M. Matsumoto, T. Haga, Hydrogen release of catalyzed lithium aluminum hydride by a mechanochemical reaction , J. Alloys Compd. 462 (2008) 275-278. 

Two mechanisms of mechanochemical reactions are most likely. First, under the action of mechanical stress, intermixing occurs at the molecular level. Second, the product forms on the surface of macroscopic reacting species. Formed in the solid phase, the radicals generated recombine so that mechanolysis proceeds as a reversible reaction. However, the term reversibility should be applied only to the bond formation between radicals. For example, the structure of recombined product can be and is different from that of the starting material. It is the main feature that disturbs conventional reversibility of the radical recombination during mechanolysis. 

Because ATP and GTP are required in many biosynthetic and mechanochemical reactions, the ability to manipulate their concentrations is particularly important in many kinetic studies. The three enzymes most commonly employed for this purpose are hexokinase, phosphofruc-tokinase, and alkaline phosphatase. Each of these enzymes offers advantages and disadvantages, and one must consider the design requirements for any particular experiment before using one of these to deplete ATP or GTP. 

Note Shearing, stretching, and grinding are typical methods for the mechanochemical generation of reactive sites, usually macroradicals, in polymer chains that undergo mechanochemical reactions. 

Processings of iron oxides at room temperature. II. Mechanochemical reaction effects on the structure and surface of pure, synthetic lepidocrocite. Mat. Res. Bull. 17 1017-1023... 

The effect of KBr pellet preparation discussed above brings about a well known - and possibly overlooked - class of mechanochemical reactions those between alkaline halogenides, such as KBr and Csl, used for IR pellets, and species, such as molecules carrying -COOH groups, which may cause an alteration of the absorption frequencies with respect to those measured in solution or Nujol [70]. The mechanochemical reactions that take place when milhng and pressing analytes with KBr to form discs for IR experiments have been recently reviewed by Fernandez-Bertran and Reguera [71]. 

In a recent study, Fernandez-Bertran et al. used mechanochemical reactions to prepare a number of hemin complexes with amino acids such as arginine, histidine, lysine, methionine and tryptophan. The basic amino acids react with the hemin peripheral propionic acid groups, while arginine is also able to form a pentacoordinated complex at the Fe(III) centre. The reactions were followed by IR and Mossbauer spectroscopies [77a]. The solid-state reaction of hemin with KCN, Na2S and various substituted imidazoles has also been investigated [77b]. 

Unfortunately the authors argue that they were performing mechanochemical reactions with mechanical energy input for the salt formation or complexation to occur, rather than just creating the required contacts between reacting crystals. Furthermore, they did not exclude moisture, reported intermediate liquid phases in various cases, and did not separate out any real solid-state reactions that might have been achieved. It is therefore not possible to discuss the results in more detail here. 

Recently, a solvent-free variation was found to be equally effective. The inorganic base Na2C03 was utilized to replace the organic base DBU in a mechanochemical reaction under high-speed vibration milling conditions [37]. The yields with diethyl bromomalonate are in the range 40-50%. 

The smallest subimit of these fullerene polymers is the C j2o dimer [368], Synthesis and examination of the properties of this molecule are, therefore, of considerable interest. Beside the solid-state mechanochemical reaction of with KCN -described in Section 3.2.3 -the dimer Cj2o can be synthesized at 5 GPa and 200 °C in good yields from a bis(ethylene-difhio)TTF-C5Q complex [369]. Cj2o is a dark brown solid that is almost insoluble in most organic solvents. 1 ts solubility decreases with increasing purity of the sample this behavior is also known for pristine C q. 

The mechanochemical reactions of aluminum were investigated under two reaction conditions, namely, during and after the milling. The active source may be different in the two reactions. However, high temperature, high pressure, and nascent surface appeared not to be active factors in this case, because preactivated aluminum was observed to react with butyl bromide even after the termination of milling. 

Mechanochemical reactions (conversion of mechanical to chemical energy and vise versa) have widely been studied. They are caused by proton transfer 533 ion exchange534,535), chelate formation270,536), redox reaction 537,538), phase transitions539,540), cis-trans transitions541, and formation of intermacromolecular complexes185. ... 

Hon D N-S (1983) Mechanochemical reactions of lignocellulosic materials Appl Polym Symp 37 461-481... 

To enhance reactivity in ceramic reactions, intimate mixtures of small particles are preferred. Vigorous grinding, however, does not only reduce the particle size. Using high energy mills, considerable local pressures and temperatures may be achieved. So-called mechanochemical reactions are very rare with fluorides ... 

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