Abiotic reagents

The research team of S.R. Rajski demonstrated that o-carboalkoxy triarylphosphines react with aryl azides to afford Staudinger ligation products bearing O-alkyl imidate linkages. In comparison, the reaction of alkyl azides with o-carbalkoxy triarylphosphines usually gives rise to amide linkages. The importance of this technique lies in its ability to couple abiotic reagents under biocompatible conditions. 

Supramolecular catalysts are by nature abiotic chemical reagents that may perform the same overall processes as enzymes, without following the detailed pathway by which the enzymes actually effect them or under conditions in which enzymes do not operate. Furthermore and most significantly, this chemistry may develop systems realizing processes that enzymes do not perform while displaying comparable high efficiencies and selectivities. 

The apparent yield of the reaction (% acrylic acid converted to 3-mercaptopropionate) was about 1-2% at 60 C and 0.3-0.4% at 25 C. Addition of tributylphosphine, a disulfide cleaving reagent, to the reaction mixture either before ot after the 2 hour Incubation, Increased the thiol yield by about a factor of two. These results suggest that abiotic reactions may Indeed be responsible for the formation of some thiols In the environment and that thiols oxidize rapidly to form disulfide compounds even under reducing conditions. A kinetic study of the Michael reaction In seawater Is currently being undertaken. 

Reactions of oxidizing inorganic sulphur may nm in the presence of strong oxidizers also w/o microorganisms, i.e., abiotically. However, microbial oxidizing is much more effective, especially at low reagent concentrations. 

Abiotic reactions include chemical transformation, which results in the formation of more simple organic compounds but not in total mineralization. An important role in these reactions is played by nucleophils -electron-excessive chemical reagents (anions or molecule), which have an undivided pair of electrons on the outer electron level (OH, Cl, Br, CN, H O, CHjOH, NHj etc.). Most important abiotic reactions are hydrolysis and nucleophile substitution. 

In some cases it is feasible to convert chemical contaminants into less harmful forms in situ by promoting abiotic chemical reactions. One interesting example is the introduction of a Fenton s reagent into a contaminated aquifer the reagent, which comprises hydrogen peroxide and an iron catalyst, produces hydroxyl radicals according to the reaction ... 

Methylation by non-enzymatic MeCoBi2 may be treated as abiotic, except that the reagent itself is produced biotically and may be re-methylated biotically. The two main abiotic methylation processes are transmethylation, and to a lesser extent photochemical. 

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