Anhydrous organic solvents

Chlorine in the presence of hydrogen chloride in an anhydrous organic solvent yields 2,4,6-trichloroariiline [634-93-5] (36,37). A mixture of aniline vapor and chlorine, diluted with an inert gas, over activated carbon at 400°C yields o-chloroaruline [95-51-2] (38). Aniline when treated with chlorine gas, in an aqueous mixture of sulfuric acid and acetic acid, at 105—115°C gives an 85—95% yield of -chlorarul [118-75-2] (39). 

Yamashita, S., Satoi, M., Iwasa, Y.etal. (2007) Utilization of hydrophobic bacterium Rho do co ecus opacusB-4 as whole-cell catalyst in anhydrous organic solvents. Applied Microbiology and Biotechnology, 74, 761-767. 

Some metal-sulfur clusters have been used in anhydrous organic solvents as C02 electrocatalysts. They lead mainly to HCOO-,183-185 except when LiBF4 is used as electrolyte, where oxalate formation is observed.186,187... 

Tris(dimethylamino)borane is a colorless liquid having a typical amine odor, b.p. 147°, nd° 1.4461. It is readily and quantitatively hydrolyzed. It is miscible without decomposition with most common nonprotonic anhydrous organic solvents. 

The formation of hydrogen does not occur in anhydrous organic solvents.32,33,63 Due to the lack of hydrogen evolution, dissolution valence is near 4 at all current densities. Addition of water in the organic solvents reduces the dissolution valence. 

For the preparation of two-dimensional materials by reaction of the same type of complex (M=Zn) in anhydrous organic solvent in the presence of 1,6-hexylamine at room temperature, or in the presence of long-chain primary amines near 200 °C [98, 109]... 

Clemmensen reduction of ketones in anhydrous organic solvents. Vedejs, E., Org. Reactions 22,401 (1975). 

In anhydrous organic solvents, ethene/CO copolymerisation termination occurs exclusively by P-H transfer to give vinyl terminated polyketone and Pd-H (Scheme 7.15c). On the other hand, traces of water are very difficult to eliminate and consequently chain transfer by protonolysis is often observed, together with p-H transfer. Experimental evidence in this sense has been straightforwardly obtained by an in situ NMR study of the chemical stability of the p-chelate [Pd(CH7CH7C(0)-Me)(dppe)]PF5 (7) in wet and anhydrous CD2CI2 [5ej. Figure 7.13 reports a sequence of P H NMR spectra taken after dissolution of the p-chelate in the wet solvent already the first spectrum at room temperature showed the formation of the p-hydroxo binuclear complex [Pd(OH)(dppe)]2(PF )2 (8), that was the only detectable species after 15 h. 

The reactions using commercially available peroxydisulfate, such as Na2S20s, K2S2O8 or (NH4)2S20g, have been generally carried out in aqueous solutions mostly in the presence of metal catalysts. It was expected that if the peroxydisulfate could be used in anhydrous organic solvents, a clean-cut reaction would take place under mild reaction conditions. 

On the other hand, in two other papers, the formation of hydrogen gas was not mentioned, whereas carbon monoxide and formic acid were both observed as products. In studies carried out by Ogura and coworkers [123], electrogenerated [Co(PPh3)2L] (where L is a substituted quinoline, bipyridine, or phenan-throline moiety) was employed as a catalyst for the reduction of CO2 in anhydrous organic solvents, conditions for which the current efficiency for production of CO (the main product) was 83%. Similarly, in an investigation done by Behar et al. [124], who used cobalt porphyrins as catalysts in an acetonitrile medium, the formation of both carbon monoxide and formic acid was noted however, the catalytic species did not appear to contain cobalt(I), but rather a cobalt(O) species complexed with carbon dioxide. 

Barbier-Grignard-type reactions in water (Li, 1996) between aUyl hahdes and carbonyl compounds can be mediated by metals of tin, zinc, or indium. Usually the generation of the organometalhc reagent takes place in anhydrous organic solvents, but using softer metals allows this reaction to take place in water. 

Figure 3.7 Catalytic activity of subtilisin in anhydrous organic solvents ( n-hexane, diisopropyl ether, T THF) as a function of the KCI content in the dry catalyst. The activity is expressed in terms of kat/Km of the transesterification reaction between N-acetyl-L-phenylalanine ethyl ester and n-propanol, used in concentrations of lOmM and 0.85 M, respectively [88].

The seminal work of Klibanov in the early 1980s [46,47] made it clear that enzymes can be used in hydrophobic organic solvents, although at the price of a severely reduced reaction rate [48, 49]. Indeed, many Upases, as well as some proteases and acylases, are so stable that they maintain their activity even in anhydrous organic solvents. This forms the basis for their successful application in non-hydrolytic reactions, such as the (enantioselective) acylation of alcohols and amines, which now are major industrial applications [50]. 

E. Vedejs, Clemmensen Reduction of Ketones in Anhydrous Organic Solvents, Organic Reactions 22, 401 (1975). 

Contrary to expectations that enzymes are only active in aqueous solution, activity in almost anhydrous organic solvents was already demonstrated in the 1930s and rediscovered in 1977. It was not water-miscible hydrophilic solvents such as methanol or acetone that proved to be the best reaction media, but hydrophobic water-immiscible solvents such as toluene or cyclohexane. Supposedly, the cause is the partitioning of water between the enzyme surface and the bulk phase of the organic solvent. As comparably hydrophilic solvents such as methanol or acetone can take up basically infinite amounts of water, they strip the remaining water molecules off the enzyme surface. As a consequence, the enzyme is no longer active because it requires a small but measurable amount of water for developing its activity... 

Enzymes are sometimes more stable in anhydrous organic solvents than in water. Lysozyme in water at 100 °C was demonstrated to be 50% deactivated after 30 s (pH 8) or after 100 min (pH 4), but after 140 h in cyclohexane or even after 200 h as a dry powder (Zaks, 1986a). 

The common mode of suspending lyophilized enzymes in organic solvents containing very little water results in just a low specific activity. Much higher specific activity can be achieved if the enzymes are dissolved in water first and then diluted with anhydrous organic solvent to the same water content (Dai, 1999) the lower the water content of the medium, the greater the discrepancy. 

A. M. Klibanov, 1989, Enzymatic catalysis in anhydrous organic solvents, Trends Biochem. Sci. 14, 141-144. 

---